JP2018142406A - All-solid battery and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an all-solid battery superior in output characteristic and a manufacturing method of the battery.SOLUTION: For solving the above problem, an all-solid battery includes: a positive electrode layer; a negative electrode layer; and a solid electrolyte layer provided between the positive electrode layer and the negative electrode layer. The positive electrode layer comprises: a positive electrode active material; and a positive electrode collector that is provided on a positive electrode mixture layer, and includes an oxide glass having the positive electrode active material and an ion conduction. A positive electrode active material is embedded in the surface of the positive collector.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an all-solid battery using a solid electrolyte and a method for manufacturing the same.

  In order to suppress deterioration of characteristics of lithium ion batteries at high temperatures and to ensure safety, all-solid batteries using a lithium ion conductive solid electrolyte instead of an electrolyte have been proposed. In particular, lithium-ion-conducting oxide-based solid electrolytes with NASICON, perovskite, and garnet structures are extremely high in thermal stability, and are therefore intensively studied for application to all-solid-state batteries.

  Patent Document 1 discloses an all-solid battery manufacturing method to which a green sheet method is applied. An active material slurry, a solid electrolyte slurry, and a current collector slurry are prepared, and green sheets prepared by coating and drying these are laminated and sintered to produce a multi-layered all solid state battery. .

Patent Document 2 discloses that the general formula (I): A _a (B _1-b S _b ) O _c (where A is selected from Na and Li, and a is 2.75 <a <3. , B is 0 <b <0.25, and c is 3 <c <3.25). A glassy oxide-based solid electrolyte is disclosed. It has been shown that this solid electrolyte can give sufficient conductivity to the solid electrolyte and / or the positive electrode even when heated to about 300 ° C. or lower when the solid electrolyte layer and / or the positive electrode is manufactured by pressing. .

  In addition, it is difficult for an all solid state battery to have both electron conductivity and ion conductivity because it is difficult to uniformly fill a solid electrolyte as compared with a lithium ion battery using a conventional electrolyte. There is a problem that it is difficult to obtain input / output characteristics. In Patent Document 3, in order to improve the input / output characteristics of an all-solid battery, an intermediate layer made of a low-hardness material is disposed between a positive electrode mixture layer made of a positive electrode active material and a solid electrolyte and a current collector, and An all-solid battery with improved electrical contact between the agent layer and the current collector is disclosed.

JP 2007-227362 A JP2015-176854 A Japanese Patent Laying-Open No. 2015-176819

  In patent document 1, in order to make the interface between a solid electrolyte and an active material adhere, and to improve electroconductivity, it sinters at about 1000 degreeC high temperature. However, depending on the type of active material used, the active material and the solid electrolyte may cause a chemical reaction due to sintering at a high temperature, and a high-resistance heterogeneous phase may be formed. Therefore, an all-solid battery that can produce a positive electrode layer and a solid electrolyte layer by integral sintering is expected regardless of the type of active material.

  Patent Document 2 discloses that a positive electrode active material layer and a positive electrode are produced by pressing a powder of a glass ceramic solid electrolyte. However, with a powder press, it is difficult to slice the solid electrolyte layer to the order of 100 μm or less. In order to obtain high input / output characteristics, it is expected to reduce the effective resistance by thinning the solid electrolyte.

  In the all solid state battery of Patent Document 3, an organic polymer or a soft metal such as In or Sn is applied as an intermediate layer. However, since these materials deteriorate or dissolve when exposed to a high temperature environment of 100 ° C. or higher, there is a problem that they cannot be used in a high temperature severe environment.

  Therefore, an object of the present invention is to provide an all solid state battery excellent in input / output characteristics.

  In order to solve the above problems, an all-solid battery according to the present invention is an all-solid battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer, The positive electrode layer includes a positive electrode current collector, and a positive electrode mixture layer provided on the surface of the positive electrode current collector and including a positive electrode active material and an oxide glass having ion conductivity, and the surface of the positive electrode current collector Is characterized in that the positive electrode active material is embedded.

  According to the present invention, it is possible to provide an all solid state battery excellent in input / output characteristics.

It is sectional drawing of the all-solid-state battery which concerns on one Embodiment of this invention. It is a cross-sectional schematic diagram of the electrode group of the all-solid-state battery which concerns on one Embodiment of this invention. It is a cross-sectional schematic diagram of the electrode group of the all-solid-state battery which concerns on one Embodiment of this invention. It is an electrode preparation process of the all-solid-state battery which concerns on one Embodiment of this invention. It is an electrode preparation process of the all-solid-state battery which concerns on one Embodiment of this invention. 2 is an electron micrograph of an electrode cross section of an all solid state battery according to Example 1. FIG.

  Hereinafter, an all-solid battery according to an embodiment of the present invention will be described. The configuration of the all-solid-state battery and the manufacturing method thereof are not limited to those shown below, and can be implemented with appropriate modifications within a range that does not change the gist thereof.

  The all-solid-state battery which concerns on one Embodiment is related with the technique which improves an input-output characteristic by enlarging the contact area of a positive electrode collector and a positive electrode active material. In particular, the all-solid-state battery according to an embodiment exhibits excellent input / output characteristics in a severe environment of a low temperature of 0 ° C. or lower to a high temperature of 80 ° C. or higher for in-vehicle and industrial use.

<All solid battery>
FIG. 1 is a schematic cross-sectional view of an all solid state battery according to an embodiment of the present invention. The all solid state battery includes a positive electrode layer 8, a negative electrode layer 6, and a solid electrolyte layer 7 (hereinafter referred to as an electrode group) disposed between the positive electrode layer 8 and the negative electrode layer 6. The electrode group is accommodated in a battery case including a positive battery case 1 and a negative battery case 2. A gasket 4 is provided inside the battery case in order to maintain the airtightness inside the case and to prevent a short circuit between the positive electrode terminal and the negative electrode terminal. The all solid state battery further includes a wave washer 4 and a spacer 5 in order to fix the electrode group.

  2 and 3 are schematic cross-sectional views of an electrode group of an all-solid battery according to an embodiment of the present invention. The electrode group of the all-solid-state battery includes a positive electrode layer 8 composed of a positive electrode current collector 9 and a positive electrode mixture layer applied to the surface of the positive electrode current collector, a solid electrolyte layer 7 including a solid electrolyte 11, and a negative electrode layer. 12. The positive electrode mixture layer includes a positive electrode active material 10 and a solid electrolyte 11, and a positive electrode active material is embedded in the surface of the positive electrode current collector 9. In this specification, when 5% or more of the surface of the positive electrode active material is in surface contact with the positive electrode current collector, it is defined that the positive electrode active material is embedded in the positive electrode current collector.

  Since the positive electrode active material is embedded in the surface of the positive electrode current collector, the contact area between the positive electrode current collector and the positive electrode active material is increased. As a result, the electron conductivity between the current collector and the positive electrode active material is improved, and high-speed charge transfer can be performed during charge and discharge without including a conductive assistant such as conductive carbon in the positive electrode mixture layer as in the past. It becomes possible.

  From the viewpoint of improving input / output characteristics, the positive electrode active material is preferably composed of one layer as shown in FIG. 3 as shown in FIG.

The solid electrolyte contained in the positive electrode layer and the solid electrolyte contained in the solid electrolyte layer are oxide glasses having ion conductivity. The oxide glass having ion conductivity is preferably a continuum only by press molding the powder. As such an oxide glass, a general formula Li _x A _y O _z (A is at least one of S, B, C, P, Al, Ti, and 1 ≦ x ≦ 3, 1 ≦ y ≦ 1 <= 2 <= z <= 4.) The glass containing the oxide represented by this is mentioned. Specifically, it preferably includes at least one of lithium, boron, sulfur, and oxygen, and more preferably includes Li ₃ BO ₃ and Li ₂ SO ₄ . For example, Li ₃ BO ₃ —Li ₂ SO ₄ glass _or Li ₃ BO ₃ —Li ₂ SO ₄ —Li ₂ CO ₃ glass can be used.

  The oxide glass having ion conductivity may have a crystal phase. This is because ionic conductivity is improved by crystallizing part of the oxide glass.

  The oxide glass having ion conductivity described above becomes a continuous body simply by press molding, and does not require sintering at a high temperature of about 1000 ° C. Therefore, the types of other materials used for the all-solid battery are not limited. For example, conventionally, when an oxide-based solid electrolyte is used, since sintering at a high temperature of about 1000 ° C. is necessary, Au, Ag, or the like has been used as a positive electrode current collector. An Al current collector often used in a lithium ion secondary battery using a non-aqueous electrolyte cannot be used together with an oxide-based solid electrolyte because of its low heat resistance. In order to use the Al current collector together with the oxide-based solid electrolyte, the Al foil can be laminated after sintering the solid electrolyte and the positive electrode mixture layer. There was a problem that the interfacial resistance with the substance was increased. Since the oxide glass having ion conductivity described above does not need to be sintered at high temperature, the Al current collector foil, the positive electrode mixture layer, and the solid electrolyte can be integrally sintered.

  The Young's modulus of the ion conductive oxide glass is preferably 40 GPa or more and 60 GPa or less. By using an oxide glass having a Young's modulus of 40 GPa or more and 60 GPa or less, the ion conductive oxide glass is deformed during press molding to form a good interface with the positive electrode active material. When the force pushed by the current collector is sufficiently exerted, the positive electrode active material is embedded on the surface of the current collector, and 5% or more of the surface area of the positive electrode is in surface contact.

  The Young's modulus of the oxide glass having ion conductivity can be controlled, for example, by adjusting the melting point.

Li ₃ BO ₃ —Li ₂ SO ₄ glass and Li ₃ BO ₃ —Li ₂ SO ₄ —Li ₂ CO ₃ glass are Li ₃ BO ₃ and L ₂ iSO ₄ , Li ₃ BO ₃ and L ₂ iSO ₄ and Li, respectively. It is obtained by mixing ₂ CO ₃ by mechanical milling in an inert atmosphere. The processing apparatus and processing conditions are not limited, but a planetary ball mill is particularly preferable, and the raw materials may be sufficiently mixed in a mortar or the like in an inert atmosphere before the milling process. The processing conditions need to be changed as appropriate according to the processing apparatus to be used, but when using a planetary ball mill, the raw materials can be mixed and reacted more uniformly as the rotational speed increases and / or the processing time increases. . Specifically, when a planetary ball mill is used, the force calculated from the acceleration of the sample and the weight of the sample is preferably 0.02N or more and processed for 1 hour to 50 hours, preferably 20 hours to 50 hours. It is more preferable that the treatment is performed within the time. The treatment atmosphere is preferably an inert atmosphere such as argon, but may be treated in an airtight state using an overpot or the like.

  In order to avoid hydrolysis reaction during mechanical milling treatment, it is preferably in an anhydrous state. When both salts contain crystal water, the temperature is 200 ° C. or higher and 600 ° C. or lower in air for 1 hour. It is preferable to dehydrate within 6 hours.

  For the positive electrode current collector, for example, aluminum and its alloys are preferable because they are inexpensive and lightweight. A sheet or mesh is used. The positive electrode current collector can be made of a material such as stainless steel or titanium in addition to the aluminum material. The positive electrode current collector is not particularly limited in material, shape, manufacturing method, and the like, and can be appropriately selected from a wide range.

As the positive electrode active material, for example, a Li-containing layered oxide typified by LiCoO ₂ , a spinel type oxide such as LiMn ₂ O ₄ , an olivine type oxide such as LiFePO _4, or the like is used. These positive electrode active materials include LiNbO ₃ , lithium nitride (Li ₃ N), Li ₇ La ₃ Zr ₂ O ₁₂ having a garnet-type structure, and Li _{1 + x + y} Al _x Ti _2-x Si _y P ₃ having a NASICON-type crystal structure. _{-y O 12 (x = 0.3,} Y = 0.2) by the solid electrolyte and the like, such as it may be coated. The positive electrode active material is preferably primary particles. The average particle diameter is preferably 5 μm or more, and more preferably 10 μm or more.

  The positive electrode mixture layer may contain a conductive additive in addition to the positive electrode active material and the oxide glass. Examples of the conductive aid include graphite such as natural graphite and artificial graphite, single-walled or multi-walled carbon nanotubes, graphene, fullerene, VGCF, acetylene black, ketjen black (trade name), channel black 6, furnace black, lamp Carbon black such as black and thermal black, carbon fiber, and the like can be used. These may be used alone or in combination of two or more. For example, in the case of particles, those having a form of aggregate such as secondary particles and chain structures are not limited to primary particles. The amount of carbon DBP oil supply (value of how much oil is retained in the voids of the structure) is 100 (ml / 100 g) or more, so that a small amount of 2.5 to 10 wt% of the positive electrode slurry solid content can be added. It becomes possible to ensure sufficient electron conductivity after high temperature storage.

  From the viewpoint of improving input / output characteristics, the thickness of the solid electrolyte layer is preferably 100 μm or less.

  For the negative electrode, metallic lithium, indium, a sheet on which a lithium alloy or silicon is vapor-deposited, or a foil thereof can be used. These negative electrodes may be formed on a current collector such as aluminum or copper foil.

  Moreover, the negative electrode may be comprised from the negative mix layer containing a negative electrode active material and a solid electrolyte, and a negative electrode electrical power collector. As the negative electrode active material, for example, Si, Si alloy, hard carbon, graphite, lithium titanate (LTO), or the like can be used.

<All-solid battery manufacturing method>
The electrode preparation process of the manufacturing method of the all-solid-state battery which concerns on one Embodiment of this invention of FIG. 4 is shown.

  An all solid state battery according to an embodiment of the present invention includes a positive electrode sheet preparation step in which a positive electrode slurry is applied and dried on a positive electrode current collector to prepare a positive electrode sheet, and a solid electrolyte slurry is molded or applied and dried into a sheet shape. A solid electrolyte sheet preparation step for preparing a solid electrolyte layer sheet, a lamination step for laminating a positive electrode sheet and a solid electrolyte sheet, and a laminate obtained by the lamination step at a temperature lower than the crystallization temperature of the oxide glass before pressing. A degreasing step of heating and degreasing, and a crystallization step of heating the degreased laminate at a temperature equal to or higher than the crystallization temperature of the oxide glass and lower than 300 ° C.

(Positive electrode sheet production process)
In the positive electrode sheet preparation step, first, a positive electrode slurry is prepared. The positive electrode slurry is prepared by mixing a positive electrode active material, an ion conductive oxide glass, and a binder solution. Here, as the solvent of the binder solution, a solvent that hardly reacts with the oxide glass powder is used. For example, ethanol, butyl acetate, dibutyl ether and the like can be mentioned. The binder is preferably one that decomposes 90% or more at less than 300 ° C., and examples thereof include methylcellulose and methylbutanetriol. These binders are used by dissolving in the above solvent in a weight ratio of 10% to 20%.

  As the ion conductive oxide glass powder, one that has been pulverized to a specific range of particle diameters by a method such as a bead mill or a ball mill is used. It is preferable to use an oxide glass powder having an average particle size of 10 μm or less, and more preferably 5 μm or less. The particle size distribution can be measured by a laser diffraction / scattering particle size distribution measuring apparatus. This is based on the median value (D50) of the particle size distribution, and is the particle size when the sum of the volumes smaller than a certain particle size occupies 50% of the total volume of the powder in the particle size distribution.

  The solid content ratio of the positive electrode slurry (the total of the positive electrode active material, the oxide glass powder, and the binder weight with respect to the weight of the slurry) is preferably 50% or more by adding a solvent as appropriate, and more preferably 70% or more. preferable.

  The ratio of the positive electrode active material to the oxide glass powder is preferably 1 or more by weight, and more preferably 4 or more. The weight ratio of the binder to the total of the oxide glass powder and the positive electrode active material is preferably less than 0.6, and more preferably less than 0.3.

  By applying the produced positive electrode slurry onto the positive electrode current collector by a doctor blade method, a screen printing method, or the like, a positive electrode sheet having a thickness after drying of 50 μm or less can be obtained.

(Solid electrolyte sheet manufacturing process)
In the solid electrolyte sheet preparation step, first, an ion conductive oxide glass powder and a binder solution are mixed to prepare a solid electrolyte slurry. A binder solution that does not chemically react with the oxide glass powder is used. Examples of the solvent that does not chemically react with the oxide glass powder include ethanol, butyl acetate, and dibutyl ether. The binder is preferably one that decomposes 90% or more at less than 300 ° C., and examples thereof include methylbutanetriol. These binders are used by dissolving in the above solvent in a weight ratio of 10% to 20%.

  As the ion conductive oxide glass powder, one that has been pulverized to a specific range of particle diameters by a method such as a bead mill or a ball mill is used. It is preferable to use an oxide glass powder having an average particle size of 10 μm or less, and more preferably 5 μm or less.

  The solid content ratio of the solid electrolyte slurry (the weight of the glass and the binder with respect to the weight of the slurry) is preferably 50% or more, more preferably 70% or more by appropriately adding a solvent. The weight ratio of the binder to the oxide glass powder is preferably less than 0.6, and more preferably less than 0.3.

  By applying and molding the prepared solid electrolyte slurry on a carrier film such as PET that has been subjected to a release treatment by a doctor blade method, a screen printing method, etc., to obtain a green sheet having a thickness of 50 μm or less after drying Can do.

  The obtained positive electrode sheet and solid electrolyte sheet are punched out to a predetermined size with a belt punch or the like, the carrier film is peeled off from the solid electrolyte sheet, and vacuum dried at 80 ° C. for 24 hours.

(Lamination process)
In the laminating step, the positive electrode sheet and the solid electrolyte sheet are laminated. After laminating, you may pressurize before degreasing. By applying pressure before degreasing, each green sheet and its interface are densified. Further, the positive electrode sheet and the solid electrolyte sheet are bonded. As a method of pressurization, using a hydraulic press or a roll press, the pressure during pressurization is preferably 100 MPa or more, more preferably 350 MPa or more in order to obtain sufficient denseness.

(Degreasing process)
The obtained laminated green sheet of the positive electrode / solid electrolyte layer is degreased below the crystallization temperature of the oxide glass and pressed to obtain an electrode in which the positive electrode and the solid electrolyte layer are integrated. The temperature at the time of degreasing should just be less than the crystallization temperature of the oxide glass contained in a positive electrode sheet and a solid electrolyte sheet. When glass ceramics are used, the Young's modulus increases, making it difficult to mold with a press after degreasing. From the viewpoint of facilitating press molding, the degreasing temperature is preferably 250 ° C. or lower. Therefore, the heat treatment temperature during degreasing is preferably 200 ° C. or higher and 250 ° C. or lower.

  Most of the binder contained in the solid electrolyte sheet is decomposed by the degreasing process, but a part of the binder remains in the solid electrolyte layer without being decomposed. The positive electrode layer and the solid electrolyte layer of the all-solid battery include a binder whose decomposition temperature is equal to or lower than the crystallization temperature of the oxide glass. From the viewpoint of reducing the residual amount of the binder, it is preferable to degrease after the lamination and before pressurization. Degreasing after lamination and before pressurization increases the number of voids in the green sheet compared to degreasing after pressurization, and the binder can be removed from these voids.

(Crystallization process)
The laminated green sheet obtained in the degreasing process is further heated at less than 300 ° C., whereby the oxide glass is partially crystallized to obtain glass ceramics with high ionic conductivity. The heat treatment temperature in the crystallization step is preferably 250 ° C. or higher and lower than 300 ° C.

(Joining process)
In the joining step, the negative electrode layer is joined to the solid electrolyte layer after the crystallization step. Specifically, metallic lithium, indium, or a lithium aluminum alloy is vapor-deposited on the solid electrolyte layer, or these foils are pressure-bonded and heated to join the negative electrode layer. When the negative electrode layer is pressure-bonded, it may be formed on a current collector such as SUS, aluminum, or copper foil.

  In addition, you may join a negative electrode layer with the following method. A negative electrode sheet is produced in the same manner as the positive electrode sheet and the solid electrolyte sheet. The negative electrode sheet is produced by molding a negative electrode slurry containing a negative electrode active material, oxide glass powder, a binder having a decomposition temperature lower than the crystallization temperature of the oxide temperature, and a solvent into a sheet shape. In the laminating step, the all-solid battery may be manufactured by laminating and pressing the positive electrode sheet, the solid electrolyte sheet, and the negative electrode sheet in this order, followed by a degreasing step and a crystallization step.

  An all solid state battery according to an embodiment of the present invention is prepared by applying a solid electrolyte slurry on a positive electrode sheet and drying to produce a laminate in which the positive electrode sheet and the solid electrolyte sheet are laminated, and then degreasing and crystallizing. It can also be produced. FIG. 5 shows an electrode manufacturing process of the all solid state battery. Applying and drying a solid electrolyte slurry containing a step of producing a positive electrode sheet, an oxide glass, a binder having a decomposition temperature lower than the crystallization temperature of the oxide glass, and a solvent, on the positive electrode sheet and the solid A step of obtaining a laminate of an electrolyte sheet, a degreasing step after degreasing less than the crystallization temperature of the oxide glass before pressurizing, and a degreasing step of pressing, and a crystallization temperature of the oxide glass after the degreasing step and less than 300 ° C And a crystallization step of heating at.

  Thus, since the positive electrode sheet and the solid electrolyte sheet can be laminated by directly applying and drying the solid electrolyte slurry on the positive electrode sheet, the process of superposing the dried positive electrode and the solid electrolyte sheet Therefore, it is possible to increase the throughput of battery manufacturing.

  As described above, the solid electrolyte layer can be thinned by applying the green sheet method to the glassy oxide solid electrolyte. Since the thickness of the solid electrolyte layer can be reduced to 100 μm or less, the output of the all-solid battery can be increased.

  Also, after the crystallization step, rather than bonding the positive electrode current collector to the positive electrode sheet side, degreasing, pressurizing, and crystallizing a laminate of the positive electrode current collector, the positive electrode mixture layer, and the solid electrolyte layer The positive electrode active material is embedded in the surface of the positive electrode current collector, and the adhesion between the positive electrode current collector and the positive electrode mixture layer is improved.

<Preparation of positive electrode active material>
Li ₂ CO ₃ as the Li source compound, Co ₃ O ₄ as the Co source compound, weighed so that the molar ratio of Li to Co is 1.03, mixed in a mortar, and hydraulic press It was compacted with a machine and formed into pellets.

The obtained pellet was heat-treated at 1000 ° C. for 10 hours in an oxygen atmosphere, and then pulverized in a mortar to synthesize a lithium-containing cobalt oxide represented by a general composition formula LiCoO ₂ having an average particle diameter of 15 μm. The composition ratio is measured by an ICP (Inductive Coupled Plasma) method, and the crystal structure is a layered structure belonging to the space group R-3m by XRD (X-ray Diffraction). It was confirmed.

Next, LiNbO ₃ was coated on the surface of the synthesized LiCoO ₂ particles. First, ethanol was dissolved in ethanol so that ethoxylithium and pentaethoxyniobium were each contained in an amount of 0.6 mol / L to prepare a precursor solution of a LiNbO ₃ reaction suppression layer.

The LiNbO ₃ precursor was coated on LiCoO ₂ using a tumbling fluidized coating apparatus (MP-01, manufactured by POWREC). LiCoO ₂ was put into a tumbling fluidized coating apparatus, and dry air was introduced as a fluidized gas. While the positive electrode active material powder was rolled up with dry air and circulated inside the tumbling fluidized coating apparatus, the LiNbO ₃ precursor solution was sprayed for 1.5 hours for coating.

Next, using a tubular electric furnace, a LiCoO ₂ positive electrode active material coated with LiNbO ₃ was obtained by heat treatment at 400 ° C. for 30 minutes in an oxygen gas atmosphere. The surface of the obtained positive electrode active material was observed with a scanning electron microscope SEM (Scanning Electron Microscope, Hitachi S-4300), and Nb was present with EDS (Energy Dispersive X-ray Spectroscopy, manufactured by Horiba Seisakusho). It was confirmed.

<Production of ion conductive oxide glass>
Li ₂ SO ₄ .H ₂ O (Wako Pure Chemical purity 98 to 102%) was heated in a vacuum oven at 300 ° C. for 2 hours and dehydrated to obtain Li ₂ SO ₄ . Similarly, Li ₃ BO ₃ (Toshima Seisakusho) was dried in a 300 ° C. vacuum oven for 2 hours. The dehydrated and dried Li ₃ BO ₃ and Li ₂ SO ₄ were mixed for 10 minutes using a mortar at a weight ratio of 9: 1 in an Ar atmosphere glove box with a dew point of −100 ° C.

The obtained mixed powder was put into a ball mill pot made of zirconia together with 70 g of a ball having a diameter of 5 mm, and sealed with a SUS overpot. Li ₃ BO ₃ —Li ₂ SO ₄ glass powder having an average particle size of 5 μm was obtained by mechanical milling treatment at a rotational speed of 370 rpm for 20 hours using a planetary ball mill (Pulverisette P-7 manufactured by Fritsch).

  In addition, said manufacturing method is based on Journal of Power Sources 270 (2014) 603-607.

  Hereinafter, a description will be given along the manufacturing procedure of the all-solid-state battery shown in FIG.

<Preparation of positive electrode slurry>
LiNbO ₃ coated LiCoO ₂ powder, Li ₃ BO ₃ —Li ₂ SO ₄ glass powder, and a binder solution dissolved in 15 wt% methylbutanetriol in butyl acetate are mixed in an environment having a dew point of −30 ° C. or less, and A slurry was prepared.

LiNbO ₃ -coated LiCoO ₂ powder and Li ₃ BO ₃ -Li ₂ SO ₄ glass powder in a weight ratio of 1: 1, and in a mortar so that the binder is 7: 3 in weight ratio to the total weight of these While mixing for 10 minutes, an appropriate amount of butyl acetate was added to form a positive electrode slurry.

<Preparation of solid electrolyte slurry>
Li ₃ BO ₃ —Li ₂ SO ₄ glass powder and a binder solution dissolved in 15 wt% methylbutanetriol in butyl acetate were mixed in an environment having a dew point of −30 ° C. or less to prepare a solid electrolyte slurry.

An appropriate amount of butyl acetate was added while mixing for 10 minutes so that the Li ₃ BO ₃ —Li ₂ SO ₄ glass powder and the binder were in a weight ratio of 7: 3 to obtain a solid electrolyte slurry.

<Preparation of positive electrode sheet>
The positive electrode sheet was formed by forming a green sheet having a thickness of about 20 μm on the aluminum current collector foil having a thickness of 15 μm from the positive electrode slurry by a doctor blade method. It dried at room temperature and punched with the belt punch, and the positive electrode sheet was obtained.

<Preparation of solid electrolyte sheet>
As with the positive electrode, the solid electrolyte sheet was formed into a green sheet having a thickness of about 50 μm by the doctor blade method.

  The solid electrolyte slurry was applied on a carrier film such as PET having been subjected to a release treatment with a doctor blade having a gap of 300 μm, dried at room temperature, and then punched with a belt punch to obtain a solid electrolyte sheet.

<Preparation of all-solid battery>
Each of the obtained green sheets was vacuum-dried at 80 ° C. for 24 hours, and then the positive electrode sheet and the solid electrolyte sheet were laminated, and pressed and unified with a hydraulic press at a pressure of 350 MPa. Then, the positive electrode and the solid electrolyte layer were integrated by degreasing at 250 ° C. in an argon atmosphere and pressing again.

By heating in this integral positive electrode and the solid electrolyte layer further _{290 ℃, Li 3 BO 3 -Li} 2 SO 4 glass by partially crystallized, the high ionic conductivity _Li 3 _BO 3 _-Li 2 SO _An electrode in which the positive electrode and the solid electrolyte layer were integrated as a _4- glass ceramic was obtained.

  The negative electrode layer was joined to the obtained electrode as follows. The negative electrode layer was joined by vacuum-depositing indium on the solid electrolyte layer side to obtain an electrode composed of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer.

  The electron micrograph of the produced electrode of FIG. 6 is shown. From FIG. 6, it was confirmed that the positive electrode active material was embedded in the surface of the current collector foil and that the oxide glass having ion conductivity became a continuous body by press molding.

  As shown in FIG. 2, a positive electrode layer 6 and a solid electrolyte layer are prepared between a stainless steel positive electrode case 1 and a negative electrode case 2 for producing a coin-type battery having a diameter of 20 mm and a thickness of 3.2 mm. 7 and negative electrode layer 8 were housed, laminated with wave washer 2 and spacer 5, and the periphery of both battery cases was caulked through gasket 3 to produce an all-solid battery.

  In Example 2, the solid electrolyte slurry was applied on the positive electrode sheet to produce a green sheet in which the positive electrode sheet and the solid electrolyte sheet were integrated, and the all solid state battery was the same as in Example 1 except that it was degreased without pressing. Was made.

(Comparative Example 1)
A positive electrode slurry was prepared in the same manner as in Example 1, and this was applied to a carrier film rather than a positive electrode current collector and dried to prepare a positive electrode sheet. The solid electrolyte sheet produced in the same manner as in Example 1 was laminated with the positive electrode sheet and pressed to produce a green sheet in which the positive electrode / solid electrolyte layer was integrated. This was degreased at 250 ° C. in an argon atmosphere, and then pressed to obtain an electrode in which the positive electrode and the solid electrolyte layer were integrated.

  A negative electrode layer was joined to the produced electrode in the same manner as in Example 1, and a positive electrode current collector was not particularly installed on the positive electrode sheet side, and an all solid battery was produced by directly contacting a spacer of a coin cell.

<Measurement of DC resistance>
The internal direct current resistance was measured for the produced all solid state batteries of Examples 1 and 2 and Comparative Example 1. The measurement method and results will be described below.

  First, the battery was placed in a constant temperature bath at 80 ° C. About each battery, it charged to 3.6 with the electric current value of the load factor of 0.02C with respect to the theoretical capacity | capacitance of the battery, and calculated | required the open circuit voltage after 1 hour. Subsequently, the maximum current is calculated from the amount of voltage drop after 10 seconds when discharging is performed at load factors of 0.02C, 0.04C, 0.2C, and 0.4C, and ΔV0.02C, ΔV0.04C, ΔV0. 2C and ΔV0.4C were determined.

  Each point in the graph in which ΔV at each current value is plotted on the vertical axis and the corresponding current value is plotted on the horizontal axis is linearly approximated by the least square method, and the slope is defined as the DC resistance R of the battery.

  The measurement results are shown in Table 1.

  As shown in Table 1, the all solid state batteries of Examples 1 and 2 in which the positive electrode was directly applied to the aluminum current collector and pressed were more than the battery of Comparative Example 1 in which the positive electrode was not directly applied to the aluminum current collector. It showed a low DC resistance. From this result, it is understood that the electron conductivity of the current collector and the positive electrode active material can be improved by embedding the positive electrode active material in the current collector and increasing the contact area.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode side battery case, 2 ... Negative electrode side battery case, 3 ... Gasket, 4 ... Wave washer, 5 ... Spacer, 6 ... Negative electrode layer, 8 ... Positive electrode layer, 9 ... Current collector, 10 ... Positive electrode active material, 11 ... Solid electrolyte, 12 ... Negative electrode

Claims (11)

An all solid state battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer disposed between the positive electrode layer and the negative electrode layer,
The positive electrode layer includes a positive electrode current collector, and a positive electrode mixture layer provided on a surface of the positive electrode current collector and including a positive electrode active material and an oxide glass having ion conductivity,
An all solid state battery, wherein the positive electrode active material is embedded in a surface of the positive electrode current collector. The all-solid-state battery according to claim 1,
The all-solid-state battery, wherein the positive electrode current collector is made of Al or an Al alloy. The all-solid-state battery according to claim 1 or 2,
The oxide glass has an Young's modulus of 40 GPa or more and 60 GPa or less. An all-solid-state battery according to any one of claims 1 to 3,
The oxide glass includes a crystal phase, and is an all solid state battery. The all-solid-state battery according to any one of claims 1 to 4,
The oxide glass includes lithium, boron, sulfur, and oxygen. The all-solid-state battery according to claim 5,
The oxide glass includes Li ₃ BO ₃ and Li ₂ SO ₄ . The all-solid-state battery according to any one of claims 1 to 6,
The all-solid-state battery, wherein the solid electrolyte layer has a thickness of 100 μm or less. It is a manufacturing method of the all-solid-state battery as described in any one of Claims 1 thru | or 7, Comprising:
A positive electrode slurry containing a positive electrode active material, the oxide glass, a binder whose decomposition temperature is lower than the crystallization temperature of the oxide glass, and a solvent is applied and dried on the positive electrode current collector to produce a positive electrode sheet. And a process of
Forming a solid electrolyte slurry by forming a solid electrolyte slurry containing the oxide glass, a binder having a decomposition temperature lower than the crystallization temperature of the oxide glass, and a solvent;
A lamination step of laminating the positive electrode sheet and the solid electrolyte sheet;
A degreasing step in which the laminate obtained by the laminating step is degreased at a temperature lower than the crystallization temperature of the oxide glass before being pressurized, and then pressurized.
A crystallization step of heating the laminated body obtained by the degreasing step at a crystallization temperature of the oxide glass or more and less than 300 ° C .;
A method for producing an all-solid-state battery. It is a manufacturing method of the all-solid-state battery as described in any one of Claims 1 thru | or 7, Comprising:
A positive electrode slurry containing a positive electrode active material, the oxide glass, a binder whose decomposition temperature is lower than the crystallization temperature of the oxide glass, and a solvent is applied and dried on the positive electrode current collector to produce a positive electrode sheet. And a process of
A solid electrolyte slurry containing the oxide glass, a binder having a decomposition temperature lower than the crystallization temperature of the oxide glass, and a solvent is applied onto the positive electrode sheet and dried to form a laminate of the positive electrode sheet and the solid electrolyte sheet. Obtaining a step;
A degreasing step in which the laminate is degreased at a temperature lower than the crystallization temperature of the oxide glass before being pressurized;
A crystallization step of heating at a crystallization temperature of the oxide glass at a temperature higher than 300 ° C. after the degreasing step;
A method for producing an all-solid-state battery. It is a manufacturing method of the all-solid-state battery according to claim 8 or 9,
After the said crystallization process, the process of joining a negative electrode layer to the said solid electrolyte sheet is provided, The manufacturing method of the all-solid-state battery characterized by the above-mentioned. It is a manufacturing method of the all-solid-state battery according to any one of claims 8 to 10,
The method for manufacturing an all-solid battery, wherein the binder is methylcellulose or methylbutanetriol.

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