JP2009181882A - Method of manufacturing lithium battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a lithium battery in which a trouble due to a difference in contraction ratios of respective members during calcination can be alleviated. <P>SOLUTION: In the manufacturing method of a lithium battery, a lamination body 10 in which electrode green sheets 13a, 13b and contraction controlling layers 15a, 15b containing inorganic substance powder having a melting point higher than a predetermined temperature are laminated in order on at least one surface of a solid electrolyte green sheet 11 is fabricated, and the lamination body 10 is calcined at a predetermined temperature. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a lithium battery, and more particularly to a method for manufacturing a lithium solid state battery.

  In recent years, lithium batteries have been widely used as power sources for portable information devices such as mobile phones and notebook PCs. Batteries used for these applications are required to have high energy density and excellent cycle characteristics as well as high safety.

  A gel polymer electrolyte in which a polymer is impregnated with an organic electrolyte has been developed as an electrolyte for a lithium battery that meets these requirements. This is because such a gel polymer electrolyte is difficult to leak because it is in the form of a gel, so that the safety of the battery can be improved. However, since the gel polymer electrolyte still contains a flammable organic electrolyte, further improvement in safety is desired, and adverse effects on the environment cannot be ignored.

  Thus, solid electrolytes have attracted attention as materials that have a low environmental burden and are excellent in safety. Since the solid electrolyte does not contain an organic solvent and there is no risk of leakage or ignition, a battery (solid battery) using the solid electrolyte has extremely excellent safety.

Conventionally, solid state batteries are manufactured as follows (see Patent Documents 1 and 2).
First, a solid electrolyte green sheet and an electrode green sheet are prepared using a slurry containing each of a solid electrolyte and an active material and a binder. Next, a solid electrolyte green sheet is laminated between electrode green sheets, and this laminate is fired. Thereby, the binder contained in each green sheet sinters, and a solid electrolyte layer and an electrode layer are combined. Subsequently, a battery is manufactured by attaching a current collector to the electrode layer.
JP 2007-5279 A JP 2007-227362 A

  However, each green sheet shrinks when exposed to a high-temperature atmosphere during firing. Generally, there is a large difference in shrinkage between the electrode green sheet and the solid electrolyte green sheet. For this reason, a strong force is applied between the layers, and there may be a problem that the solid electrolyte layer and the electrode layer are cracked or delamination occurs.

  This invention is made | formed in view of the above situation, and it aims at providing the manufacturing method of the lithium battery which can relieve the malfunction resulting from the difference in the shrinkage | contraction rate of each member in baking.

  In order to complete the present invention, the present inventors have found that by disposing a layer containing an inorganic substance powder having a melting point exceeding the firing temperature on the outside of the laminate, shrinkage of the entire laminate during firing is suppressed. It came. Specifically, the present invention provides the following.

(1) A solid electrolyte green sheet containing a powder of oxide glass exhibiting lithium ion conductivity after heat treatment or a solid electrolyte layer having a lithium ion conductive crystal, and an electrode green sheet containing an active material that absorbs and releases lithium ions And a method of manufacturing a lithium battery using
Producing a laminate in which the electrode green sheet and a shrinkage suppression layer containing a powder of an inorganic substance having a melting point exceeding a predetermined temperature are sequentially laminated on at least one surface of the solid electrolyte green sheet or the solid electrolyte layer;
The manufacturing method of a lithium battery which has the procedure which bakes the said laminated body at the said predetermined temperature.

In general, the shrinkage rate in firing is such that the solid electrolyte green sheet is larger than the electrode green sheet, and the solid electrolyte layer obtained by firing the solid electrolyte green sheet is smaller than the electrode green sheet. For this reason, when a laminate of the solid electrolyte green sheet or solid electrolyte layer and the electrode green sheet is fired, there may be a problem that the solid electrolyte layer or electrode layer is broken or delamination occurs.
According to invention of (1), the shrinkage | contraction suppression layer containing the powder of an inorganic substance with melting | fusing point higher than the temperature of baking is arrange | positioned on the outer side of a laminated body, and an inorganic substance does not melt | dissolve in baking but does not shrink | contract substantially. For this reason, shrinkage of each green sheet or layer sandwiched between the shrinkage suppression layers is strongly suppressed. Thereby, the malfunction resulting from the difference in the shrinkage | contraction rate of each member in baking can be relieved.

  (2) The method for producing a lithium battery according to (1), wherein the area shrinkage ratio of the solid electrolyte green sheet or the electrode green sheet in firing is 10% or less.

  (3) The thickness of the said solid electrolyte green sheet is a manufacturing method of the lithium battery as described in (1) or (2) which is 50% or less of the thickness of the said laminated body.

  (4) The method for manufacturing a lithium battery according to any one of (1) to (3), wherein the thickness of the shrinkage suppression layer is 10% or more of the thickness of the laminate.

  (5) The method for producing a lithium battery according to any one of (1) to (4), wherein the inorganic substance has a melting point of 1100 ° C. or higher.

  (6) The method for producing a lithium battery according to any one of (1) to (5), wherein the oxide glass powder has an average particle size of 5 μm or less.

  (7) The method for producing a lithium battery according to any one of (1) to (6), wherein the maximum particle diameter of the oxide glass powder is 20 μm or less.

  (8) The method for producing a lithium battery according to any one of (1) to (7), wherein the powder of the inorganic substance has an average particle diameter of 5 μm or less.

  (9) The method for producing a lithium battery according to any one of (1) to (8), wherein the maximum particle diameter of the inorganic substance powder is 20 μm or less.

  (10) The lithium battery according to any one of (1) to (9), wherein the solid electrolyte green sheet or the solid electrolyte layer, the electrode green sheet, and the shrinkage suppression layer are laminated at a lamination pressure of 1 MPa or more. Method.

(11) The powder of the oxide glass has an ionic conductivity of 1 × 10 ⁻⁴ Scm ⁻¹ or more at 25 ° C. after the heat treatment under the same conditions as the firing. A method for producing a lithium battery as described above.

(12) The method for producing a lithium battery according to any one of (1) to (11), wherein the solid electrolyte layer after firing has an ionic conductivity of 1 × 10 ⁻⁵ Scm ⁻¹ or more at 25 ° C.

(13) The powder of the oxide glass is Li _{1 + x + y} M _x (Ge _1−y Ti _y ) _2−x Si _z P _3−z O ₁₂ (wherein M is selected from the group consisting of Al and Ga 1 The lithium battery according to any one of (1) to (12), wherein the lithium battery includes a crystal represented by the following formula: 0 ≦ x ≦ 0.8, 0 ≦ y ≦ 1.0, and 0 ≦ z ≦ 0.6 Manufacturing method.

(14) The solid electrolyte after firing is expressed in mol%,
Li ₂ O: 12-18% and / or
_{Al 2 O 3 + Ga 2 O} 3: 5~10%, and / or,
_{TiO 2 + GeO 2: 35~45%} , and / or,
SiO ₂ : 1-10% and / or
P ₂ O _5: 30~40%
The manufacturing method of the lithium battery in any one of (1) to (13) containing the glass ceramics containing this.

  According to the present invention, the shrinkage-suppressing layer containing an inorganic substance powder having a melting point higher than the firing temperature is disposed outside the laminate, and the inorganic substance does not melt during firing and does not substantially shrink. For this reason, shrinkage of each green sheet or layer sandwiched between the shrinkage suppression layers is strongly suppressed. Thereby, the malfunction resulting from the difference in the shrinkage | contraction rate of each member in baking can be relieved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

  FIG. 1 is a diagram illustrating an aspect of the manufacturing method according to the present embodiment, and FIG. 2 is a diagram illustrating another aspect of the manufacturing method according to the present embodiment. As shown in FIGS. 1 and 2, the method of manufacturing a lithium battery according to the present embodiment includes a procedure for producing a laminate, a procedure for firing the laminate, and a procedure for attaching a current collector to the laminate. Have.

<Material>
First, materials used in the present invention will be described. In the present specification, the “green sheet” refers to an unfired body of glass powder or crystal (ceramics or glass ceramics) powder formed into a thin plate, and specifically, glass powder, crystals (ceramics or ceramics). (Glass ceramics) Powder and organic binder, plasticizer, solvent etc. mixed slurry, doctor blade, calendar method, spin coating, dip coating, etc. coating method, inkjet, bubble jet, offset printing method, die coater method , Which is formed into a thin plate by a spray method or the like. The “green sheet” also includes a green sheet or a green sheet fired body in which a mixed slurry is applied.

  In addition, the green sheet is preferably formed to have a uniform thickness in that it is uniformly heated during firing and a dense sintered body having a porosity of 20 vol% or less can be easily manufactured. Therefore, the variation in the thickness of the green sheet is preferably + 10% or more and −10% or less with respect to the average value of the green sheet thickness distribution. Moreover, it is preferable that the composition of the green sheet is made uniform by thoroughly mixing the raw materials and densified by pressing with a roll press, uniaxial, isotropic pressing or the like before firing. Therefore, the mixing of the raw materials is preferably performed for 1 hour or more in a ball mill, for example.

[Solid electrolyte green sheet]
The solid electrolyte green sheet is obtained by forming a slurry containing oxide glass powder exhibiting lithium ion conductivity after heat treatment, an organic binder, a plasticizer, a solvent, and the like into a thin plate shape.

(Oxide glass powder)
The oxide glass powder is preferably a glass powder that exhibits lithium ion conductivity by heat treatment. Such glass is expressed in mol% based on oxide,
Li ₂ O: 12-18% and / or
_{Al 2 O 3 + Ga 2 O} 3: 5~10%, and / or,
_{TiO 2 + GeO 2: 35~45%} , and / or,
SiO ₂ : 1-10% and / or
P ₂ O _5: 30~40%
It is more preferable that it contains.

The glass in _{Li 1 + x + y M x} (Ge 1-y Ti y) 2 _{over x Si z P 3-z O} 12 ( wherein the heat treatment, M is at least one element selected from the group consisting of Al and Ga, 0 ≦ x ≦ 0.8, 0 ≦ y ≦ 1.0, and 0 ≦ z ≦ 0.6) are precipitated to form glass ceramics, which exhibit high lithium ion conductivity.

  Here, the glass ceramic is a material obtained by heat-treating glass to precipitate a glass phase, and specifically comprises an amorphous solid and a crystal. Such glass ceramics are preferable in that they have almost no vacancies or crystal grain boundaries that hinder ion conduction, and are excellent in ion conductivity and chemical stability. Glass ceramics include materials in which the entire glass phase has undergone a phase transition to a crystal phase, that is, a material whose crystal content (crystallinity) in the material is 100% by mass.

  Moreover, you may include said glass ceramic powder in a green sheet with oxide glass.

  The powder is produced by pulverizing the above oxide glass using a ball mill, a jet mill or the like. The average particle size of the powder when mixed with the organic binder is preferably 5 μm or less, more preferably 3 μm or less, and most preferably 1 μm or less in terms of obtaining a high filling rate. In addition, the lower limit of the average particle diameter of the powder is preferably 0.01 μm or more, more preferably 0.05 μm or more, and most preferably 0.1 μm or more, from the viewpoint that uniform dispersibility can be improved. Here, the “average particle diameter” is a D50 (cumulative 50% diameter) value (volume basis) measured by a laser diffraction method. For example, a particle size distribution measuring device “LS100Q” (manufactured by Beckman Coulter) Or a submicron particle analyzer “N5” (manufactured by Beckman Coulter, Inc.). These apparatuses may be appropriately selected according to the particle diameter of the object to be measured. Specifically, when the maximum particle diameter is less than 3 μm, measurement may be performed using only the submicron particle analyzer “N5”.

  In addition, the upper limit of the maximum particle size (maximum value of the particle size) of the oxide glass is preferably 20 μm or less, more preferably 12 μm or less, and most preferably 9 μm or less in that a high filling rate can be obtained. The lower limit of the maximum particle diameter is preferably 0.001 μm or more, more preferably 0.005 μm or more, and most preferably 0.01 μm or more, from the viewpoint that uniform dispersibility can be improved.

  The lower limit of the content of the powder when mixed with the organic binder is preferably 50% by mass or more, more preferably 55% by mass or more, based on the whole mixed slurry in that the voids after firing can be reduced. Most preferably, it is 60 mass% or more. The lower limit of the content of the oxide glass powder in the solid electrolyte green sheet after drying is preferably 50% by mass or more, more preferably 55% by mass or more, and most preferably 60% by mass or more. is there.

  The upper limit of the content of the powder is preferably 97% by mass or less, more preferably 94% by mass or less, and most preferably 90% by mass with respect to the entire mixed slurry in that the shape retention of the green sheet can be improved. % Or less. The upper limit of the content of the oxide glass powder in the solid electrolyte green sheet after drying is preferably 97% by mass or less, more preferably 94% by mass or less, and most preferably 90% by mass or less. is there.

The oxide glass powder has an ionic conductivity of 1 × 10 ⁻⁴ Scm ⁻¹ or more at 25 ° C. after heat treatment under the same conditions as firing described later, in that a high capacity and high output lithium battery can be easily manufactured. More preferably, it is 5 × 10 ⁻⁴ Scm ⁻¹ or more, and most preferably 1 × 10 ⁻³ Scm ⁻¹ or more. In addition, lithium ion conductivity refers to the property that the lithium ion conductivity exhibits a value of 1 × 10 ⁻⁸ Scm ⁻¹ or more at 25 ° C.

(Organic binder)
As the organic binder, commercially available binders widely used as molding aids for press molding, rubber press, extrusion molding, and injection molding can be used. Specific examples include acrylic resin, ethyl cellulose, polyvinyl butyral, methacrylic resin, urethane resin, butyl methacrylate, vinyl copolymer and the like. In addition to these, it is preferable to add an appropriate amount of a dispersant for improving the dispersibility of the particles, a surfactant for improving foam removal during drying, and the like.

  The lower limit of the content of the organic binder is preferably 1% by mass or more, more preferably 3% by mass or more, more preferably 5% by mass with respect to the total amount of the mixed slurry in that the ability to maintain the sheet shape can be improved. The above is most preferable. Further, the lower limit of the content in the green sheet after drying is preferably 3% by mass or more, more preferably 5% by mass or more, and most preferably 7% by mass or more.

  Further, the upper limit of the content of the organic binder is preferably 50% by mass or less, more preferably 40% by mass or less, with respect to the total amount of the mixed slurry, in that the voids after degreasing can be sufficiently reduced. 30% by mass or less is most preferable. The upper limit of the content in the green sheet after drying is preferably 40% by mass or less, more preferably 35% by mass or less, and most preferably 30% by mass or less.

(solvent)
In order to improve the dispersibility of the oxide glass powder, a solvent may be used. As such a solvent, known materials such as PVA, IPA, butanol and the like can be used, and alcohol or water is preferable in terms of reducing the environmental load. In order to obtain a more homogeneous and dense solid electrolyte, an appropriate amount of a dispersant may be used in combination, and an appropriate amount of a surfactant may be used in combination in order to improve foam removal efficiency during drying.

(Other)
The solid electrolyte green sheet may further include a Li-containing inorganic compound that functions as a sintering aid for bonding the glass ceramic particles. Among these, Li ₃ PO ₄ , LiPO ₃ , LiI, LiN, Li ₂ O, Li ₂ O ₂ , and LiF soften and melt at the time of sintering and fill the gaps in the oxide glass powder. As a result, the oxide glass powder It is preferable at the point which can couple | bond together firmly.

In addition, the solid electrolyte green sheet preferably contains a small amount of insulating crystal or glass having high dielectric properties in that lithium ion conductivity can be improved by promoting diffusion of lithium ions. For _{example, BaTiO 3, SrTiO 3, Nb 2} O 5, LaTiO 3.

[Production of solid electrolyte green sheet]
The solid electrolyte green sheet is usually obtained by forming a slurry obtained by mixing the above components into a thin plate shape on a support made of PET or the like that has been subjected to a release treatment, and then removing the thin film. Produced. However, in order to adjust the thickness of the solid electrolyte layer after firing, the sheets may be overlapped using a solid electrolyte green sheet as a support, or a solid electrolyte described later may be used as a support. Such molding may be performed by a known method such as a doctor blade or calendar method, as described above.

  The upper limit of the thickness of the green sheet after molding is preferably 200 μm or less, more preferably 150 μm or less, and most preferably 100 μm or less, from the viewpoint of suppressing the generation of cracks in the drying step described later. In addition, the lower limit is preferably 0.1 μm or more, more preferably 0.5 μm or more, and most preferably 1.0 μm or more in terms of ensuring excellent operability.

  The solid electrolyte sheet obtained in this manner may be processed into an arbitrary shape as necessary. In order to improve the denseness of the solid electrolyte layer after firing, the solid electrolyte sheet is roll-pressed, uniaxially Or you may pressurize by isotropic pressurization.

[Solid electrolyte layer]
A solid electrolyte layer may be used instead of the solid electrolyte green sheet. The solid electrolyte layer is obtained by firing a solid electrolyte sheet. For this reason, the shrinkage | contraction rate in baking after lamination | stacking is small, and the malfunction accompanying shrinkage can be suppressed more reliably. In addition, when a solid electrolyte layer is used and only one of the electrode green sheets described below is used, the shrinkage suppression layer may not be disposed adjacent to the exposed solid electrolyte layer. The firing procedure will be described later.

[Electrode green sheet]
The electrode green sheet contains an active material that absorbs and releases lithium ions, and may also contain components similar to those of the solid electrolyte green sheet, such as an organic binder and a solvent. The electrode green sheet includes a positive electrode green sheet and a negative electrode green sheet.

  As the active material contained in the positive electrode green sheet, for example, a transition metal oxide containing at least one selected from the group consisting of manganese, cobalt, nickel, vanadium, niobium, molybdenum, and titanium can be used.

  The lower limit of the content of the positive electrode active material is preferably 40% by mass or more, more preferably 50% by mass or more, and 60% by mass because the density after firing is low and the shrinkage is large if the content is too small. The above is most preferable.

  Further, the upper limit of the content of the positive electrode active material is preferably 97% by mass, more preferably 94% by mass, since flexibility is reduced and handling becomes difficult if it is excessive. Most preferably, it is at most mass%.

  Since many positive electrode active materials have poor electron conductivity and ion conductivity, it is preferable to use an electron conduction aid such as conductive carbon, graphite, carbon fiber, metal powder, and metal fiber in combination. It is preferable to use an ion conduction aid such as glass ceramics in combination. The addition amount of these electron conduction assistants and ion conduction assistants is preferably 3 to 35% by mass, more preferably 4 to 30% by mass, and most preferably 5 to 25% by mass with respect to the positive electrode material. %.

  The content of the positive electrode active material in the above slurry is preferably 10% by mass or more, more preferably 15% by mass or more, and most preferably 20% by mass or more in terms of excellent applicability. .

  The active material contained in the negative electrode green sheet is preferably an alloy such as metallic lithium, lithium-aluminum alloy, lithium-indium alloy, a transition metal oxide such as titanium or vanadium, or a carbon-based material such as graphite. The lower limit of the content of the active material is preferably 40% by mass or more, more preferably 50% by mass or more, and more preferably 60% by mass or more because if the content is too low, the density after firing is low and the shrinkage is large. Most preferably. In addition, the upper limit of the content of the active material is preferably 97% by mass, more preferably 94% by mass, and 90% by mass because flexibility is reduced and handling becomes difficult if it is excessive. % Is most preferred.

  When the negative electrode active material has poor electron conductivity, it is preferable to use an electron conduction aid such as conductive carbon, graphite, carbon fiber, metal powder, metal fiber, etc., and ion conduction aid such as ion conductive glass ceramics. It is preferable to use an agent in combination. The addition amount of these electron conduction assistant and ion conduction assistant is preferably 3 to 35% by mass, more preferably 4 to 30% by mass, and most preferably 5 to 25% by mass with respect to the negative electrode material. It is.

  The content of the negative electrode active material in the above slurry is preferably 10% by mass or more, more preferably 15% by mass or more, and most preferably 20% by mass or more in terms of excellent applicability. .

  These electrode green sheets preferably contain the same oxide glass powder as that contained in the solid electrolyte. Thereby, since the ion movement mechanism in the electrolyte layer and the electrode layer is unified, the ion movement between the electrolyte layer and the electrode layer is smoothly performed, and the output and capacity of the battery can be improved.

  The lower limit of the content of the oxide glass powder in the mixed slurry is preferably 1% by mass or more, and preferably 3% by mass or more, based on the total amount of the mixed slurry, in that lithium ion conductivity can be reliably imparted. Is more preferable, and most preferably 5% by mass or more. The lower limit of the content of the oxide glass powder in the electrode green sheet after drying is preferably 3% by mass or more, more preferably 5% by mass or more, and 10% by mass or more. Is most preferred.

  The upper limit of the content of the oxide glass powder in the mixed slurry is 50% by mass or less based on the total amount of the mixed slurry because the amount of the active material is relatively small and the battery capacity tends to be insufficient when it is excessive. It is preferably 40% by mass or less, and most preferably 30% by mass or less. The upper limit of the content of the oxide glass powder in the electrode green sheet after drying is preferably 70% by mass or less, more preferably 60% by mass or less, and 50% by mass or less. Is most preferred.

[Shrinkage suppression layer]
A shrinkage | contraction suppression layer contains the powder of the inorganic substance which has melting | fusing point exceeding the below-mentioned baking temperature (predetermined temperature). In addition, you may contain the component similar to a solid electrolyte green sheet, such as an organic binder and a solvent. The predetermined temperature may be appropriately set according to the composition of each green sheet and layer, and details will be described later.

The melting point of the inorganic substance is preferably 1100 ° C. or higher, more preferably 1150 ° C. or higher, and most preferably 1200 ° C. or higher in view of obtaining sufficient shrinkage suppressing ability. Examples of such inorganic substances include metal oxides such as Y ₂ O ₃ , ZrO ₂ , CaO, Al ₂ O ₃ , Ce ₂ O ₃ , Gd ₂ O ₃ , Sc ₂ O _3, and Eu ₂ O ₃ , Nb, Examples include simple substances, compounds or alloys of refractory metals such as Ta, Mo, and W. Of these, easily and industrially available and green sheets formed easily in _terms, preferably ZrO 2, CaO and _Al 2 _{O 3,} more preferably CaO and _Al 2 _{O 3,} and most preferably is _Al 2 _{O 3} .

  The inorganic substance powder is produced by pulverizing the above inorganic substance using a ball mill, a jet mill or the like. The average particle size of the powder when mixed with the organic binder is preferably 20 μm or less, more preferably 15 μm or less, and most preferably 10 μm or less in that a high filling rate is obtained. The lower limit of the average particle diameter of the powder is preferably 0.05 μm or more, more preferably 0.1 μm or more, and most preferably 0.3 μm or more in that it can be easily removed after firing. The definition and measuring method of “average particle diameter” are as described above.

<Production of laminate>
In this procedure, a laminate in which an electrode green sheet and a shrinkage suppression layer are sequentially laminated on at least one surface of a solid electrolyte green sheet or a solid electrolyte layer is produced. This laminate does not include a current collector green sheet, and it is preferable to attach the current collector to the sintered laminate after firing. Thereby, the permissible range of firing conditions (for example, temperature and atmosphere) is widened, industrial production is dramatically facilitated, the current collector material options are greatly increased, and versatility can be improved. The structure of such a laminate will be specifically described with reference to FIGS.

  As shown in FIG. 1, in the laminate 10 in one embodiment, an electrode green sheet and a shrinkage suppression layer are sequentially laminated on both surfaces of a solid electrolyte green sheet or a solid electrolyte layer. That is, the positive electrode green sheet 13a is disposed on one surface of the solid electrolyte green sheet or the solid electrolyte layer 11, and the first shrinkage suppression layer 15a is disposed on the positive electrode green sheet 13a. Moreover, the negative electrode green sheet 13b is arrange | positioned at the other surface of the solid electrolyte green sheet or the solid electrolyte layer 11, and the 2nd shrinkage | contraction suppression layer 15b is arrange | positioned under this negative electrode green sheet 13b.

  As shown in FIG. 2, in the laminate 10 </ b> A in another aspect, the electrode green sheet and the shrinkage suppression layer are sequentially laminated on one surface of the solid electrolyte green sheet or the solid electrolyte layer. That is, the positive electrode green sheet 13a is disposed on one surface of the solid electrolyte green sheet or the solid electrolyte layer 11, and the first shrinkage suppression layer 15a is disposed on the positive electrode green sheet 13a. On the other hand, the negative electrode green sheet is not disposed on the other surface of the solid electrolyte green sheet or the solid electrolyte layer 11. Here, when the code | symbol 11 is the solid electrolyte after baking, a 2nd shrinkage | contraction suppression layer does not need to be arrange | positioned. When the code | symbol 11 is a solid electrolyte green sheet, a 2nd shrinkage | contraction suppression layer (not shown) is directly arrange | positioned on the other surface of the solid electrolyte green sheet 11. FIG.

  Note that the order of superposition is not particularly limited as long as the laminate has the above structure as a result. That is, first, an electrode green sheet may be superimposed on the solid electrolyte green sheet or the solid electrolyte layer, and then a shrinkage suppression layer may be superimposed on the electrode green sheet, or the solid electrolyte green sheet or the solid electrolyte layer An electrode green sheet may be sandwiched between the shrinkage suppression layer. Further, as described above, each green sheet may be directly formed on a green sheet to be superimposed, or on ceramics or the like.

  After superposing all the green sheets or layers, lamination is performed at a predetermined lamination pressure. The lower limit of the lamination pressure is preferably 1 MPa or more, more preferably 3 MPa or more, and most preferably 5 MPa or more in that a stable laminated structure is obtained. Further, the upper limit of the lamination pressure is preferably 1000 MPa or less, more preferably 800 MPa or less, and most preferably 600 MPa or less, in that each green sheet or layer is not easily damaged.

  In the laminated body thus produced, the upper limit of the thickness T3 of the solid electrolyte green sheet 11 is preferably 50% or less of the thickness Tt of the laminated body 10 and more preferably from the viewpoint that defects due to shrinkage are less likely to occur. 40% or less, most preferably 30% or less. Further, the lower limit of the thickness T3 is preferably 0.1% or more, more preferably 0.3% or more, and most preferably the thickness Tt of the laminate 10 in that the function as an electrolyte can be sufficiently secured. 0.5% or more.

  Further, the lower limit of the thickness of the shrinkage suppression layer, that is, the sum of the thickness T1 of the first shrinkage suppression layer 15a and the thickness T2 of the second shrinkage suppression layer 15b is that the shrinkage can be sufficiently suppressed, It is preferably 10% or more, more preferably 15% or more, and most preferably 20% or more. Further, the upper limit of the sum of the thickness T1 and the thickness T2 is preferably 95% or less, more preferably 90% or less, and most preferably 85% of the thickness Tt of the laminate 10 in terms of preventing cost waste. It is as follows.

  In addition, the description regarding the above thickness is appropriate also about the case where one of the electrode green sheets is not laminated | stacked like the laminated body 10A shown by FIG.

<Baking>
Subsequently, the laminate is fired. This procedure generally includes a degreasing process and a sintering process. These steps are preferably performed while exchanging air in a gas furnace, microwave furnace, electric furnace or the like.

[Degreasing]
The stacked body is heated at a relatively low temperature (for example) to remove the organic binder. Thereby, since the organic binder etc. which were contained in each green sheet and layer are decomposed | disassembled and gasified and discharged | emitted from a laminated body, organic substance can be removed. The lower limit of the heating temperature is preferably 360 ° C. or higher, more preferably 380 ° C. or higher, and most preferably 400 ° C. or higher in terms of sufficiently removing organic substances. In addition, the upper limit of the heating temperature is preferably 700 ° C. or less, more preferably 680 ° C. or less, and most preferably 660 ° C. or less from the viewpoint that the oxidation of the metal material can be suppressed.

[Sintering]
The laminated body after the degreasing step is fired at a predetermined temperature higher than the temperature in the degreasing step. Thereby, oxide glass and an active material are baked and hardened. The lower limit of the predetermined temperature is preferably 750 ° C. or higher, more preferably 800 ° C. or higher, and most preferably 850 ° C. or higher in that each layer can be sufficiently densified. In addition, the upper limit of the predetermined temperature is preferably 1100 ° C. or less, more preferably 1080 ° C. or less, and most preferably 1060 ° C. or less from the viewpoint of suppressing a decrease in strength of the material. From another point of view, the predetermined temperature is preferably 50 ° C. or more lower than the melting point of the inorganic substance, more preferably 100 ° C. or more, and most preferably, from the viewpoint that a sufficient range of options for the material of the shrinkage suppression film can be secured. 150 ° C. or higher.

The solid electrolyte layer 21 of the sintered laminate 20 formed after such firing is 1 × 10 ⁻⁵ Scm ⁻¹ or more at 25 ° C. in that a high capacity and high output lithium battery can be easily manufactured. It preferably has ionic conductivity, more preferably 5 × 10 ⁻⁵ Scm ⁻¹ or more, and most preferably 1 × 10 ⁻⁴ Scm ⁻¹ or more.

  Further, the area shrinkage ratio of the solid electrolyte green sheet or the electrode green sheet in firing is preferably 10% or less, more preferably 5% or less, and most preferably 3% or less, from the viewpoint of suppressing problems due to shrinkage. is there. Area shrinkage is the percentage of the difference between the area of the solid electrolyte green sheet or electrode green sheet before firing and the difference of the area of the solid electrolyte layer or electrode layer after firing subtracted from the area of the solid electrolyte green sheet or electrode green sheet It is. The area shrinkage ratio may be measured based on the solid electrolyte green sheet when both electrode green sheets are laminated, and either the solid electrolyte green sheet or the electrode green sheet when only one electrode green sheet is laminated. Or may be measured based on both.

  It is preferable to remove the shrinkage suppression layers 25a and 25b before the next current collector is attached. Since the shrinkage suppression layers 25a and 25b after firing are usually extremely brittle, they can be easily removed. It is preferable to perform ultrasonic cleaning after the removal.

  In addition, as shown in FIG. 2, when one electrode green sheet is not included in the laminate 10A before firing, it is necessary to form the electrode layer 23bA after the removal of the shrinkage suppression layer 21. As is well known in the art, the electrode layer can be formed by applying an electrode slurry containing an active material, an organic binder and the like to the solid electrolyte layer and baking it.

<Installation of current collector>
Subsequently, a current collector is attached to the electrode layer of the sintered laminate. Usually, a collector slurry containing a collector powder, an organic binder, and the like is applied to the electrode layer, and the coated material is fired.

  As the current collector powder, a metal material having electronic conductivity is used. Specific examples include at least one selected from the group consisting of aluminum, copper, nickel, palladium, gold, and platinum.

  The current collector slurry may contain a glass frit having heat-fusibility. The softening point of glass frit should just be about 400-700 degreeC, and content of glass frit should just be 0.5-15 mass parts per 100 mass parts of collector powder. Other materials to be used and the firing procedure may be the same as described above.

  Thereafter, in order to output electricity to the outside, a lithium battery is manufactured by providing a lead on the current collector. Lead materials and lead installation procedures are well known in the art.

  Note that the order of forming the negative electrode layer, attaching the current collector, and connecting the leads may be changed as appropriate, and is not limited to the order of the above-described or following embodiments.

[Production of solid electrolyte green sheet]
As raw materials, H ₃ PO ₄ , Al (PO ₃ ) ₃ , Li ₂ CO ₃ , SiO ₂ , and TiO ₂ were used, and these raw materials were mol% in terms of oxide, P ₂ O 533.8%, Al _{2 O 3 7.6%, Li 2} O14.5%, SiO 2 2.8%, were weighed so that TiO 2 41.3% of the composition, were homogeneously mixed. The mixture was put in a platinum pot and heated and dissolved in an electric furnace at 1450 ° C. for 3 hours with stirring. The obtained glass melt was dropped into running water to obtain flaky glass. By pulverizing this glass with a jet mill, glass particles having an average particle diameter of 1.9 μm were obtained, and the glass particles were finely pulverized with a wet ball mill using ethanol, and the resulting slurry was spray-dried to obtain an average particle diameter. 0.3 micrometer glass microparticles were obtained.

  A slurry was prepared by adding a dispersant to an acrylic resin dispersed in water to glass fine particles, and stirring for 48 hours with a ball mill. The content of glass fine particles in this slurry was 65.5% by mass, and the content of acrylic resin was 13.5% by mass. The slurry was molded with a thickness of 15 μm on a PET film which had been subjected to a release treatment by the doctor blade method, and was subjected to primary drying at 80 ° C. and further secondary drying at 95 ° C. to obtain a sheet-like material. . A dense green sheet was produced by superimposing two sheet-like materials after peeling the PET film and applying pressure at 196.1 MPa for 10 minutes using an isotropic pressure device (CIP). . In addition, superposition | stacking and lamination | stacking are arbitrary processes.

In addition, in order to confirm the state of the produced green sheet, the green sheet was cut into a 50 mm square and fired at 900 ° C. for 3 hours. When the fired product was examined by X-ray diffraction, the main crystal phase was Li _{1 + x + y} AlTi _2−x Si _y P _3−y O ₁₂ (wherein 0 ≦ x ≦ 0.4, 0 <y ≦ 0). .6). Moreover, the ionic conductivity obtained by performing impedance measurement was 1.5 × 10 ⁻⁴ Scm ⁻¹ .

[Preparation of positive electrode green sheet]
The flake glass obtained in the process of producing the solid electrolyte sheet is heat-treated at 870 ° C. for 5 hours, so that the main crystal phase is Li _{1 + x + y} AlTi _2−x Si _y P _3−y O ₁₂ (where 0 ≦ x ≦ 0.4, 0 <y ≦ 0.6), and a flaky solid electrolyte having an ionic conductivity of 1.5 × 10 ⁻⁴ Scm ⁻¹ was obtained. This solid electrolyte was pulverized using a jet mill and a wet ball mill to obtain a solid electrolyte powder having an average particle size of 0.2 μm. This solid electrolyte powder was mixed with commercially available LiCoO ₂ (average particle diameter 7.5 μm) using a ball mill (solid electrolyte: LiCoO ₂ = 25: 75 (mass ratio)).

  To this composite, a dispersant was added to an acrylic resin dispersed in water, and a slurry was prepared by stirring for 48 hours with a ball mill. The content of the composite in this slurry was 62.1% by mass, and the content of the acrylic resin was 15.2% by mass. The slurry was molded at a thickness of 45 μm on a PET film that had been subjected to a release treatment by the doctor blade method, and was subjected to primary drying at 80 ° C. and further secondary drying at 95 ° C. to obtain a sheet-like material. . A dense green sheet was produced by superimposing two sheet-like materials after peeling the PET film and applying pressure at 196.1 MPa for 10 minutes using an isotropic pressure device (CIP). . In addition, superposition | stacking and lamination | stacking are arbitrary processes.

[Production of negative electrode green sheet]
A commercially available 7.5 μm average Li _4/3 Ti _5/3 O ₄ was pulverized to a mean particle size of 1.4 μm using a wet ball mill, and mixed with the above solid electrolyte powder using a ball mill (Li _{4 / 3} Ti _5/3 O ₄ : Solid electrolyte = 80: 20 (mass ratio)).

  To this composite, a dispersant was added to an acrylic resin dispersed in water, and stirred for 48 hours with a ball mill to prepare a slurry. The content of the composite contained in the slurry at this time was 60.8% by mass, and the content of the acrylic resin was 14.8% by mass. The slurry was molded at a thickness of 45 μm on a PET film that had been subjected to a release treatment by the doctor blade method, and was subjected to primary drying at 80 ° C. and further secondary drying at 95 ° C. to obtain a sheet-like material. . A dense green sheet was produced by superimposing two sheet-like materials after peeling the PET film and applying pressure at 196.1 MPa for 10 minutes using an isotropic pressure device (CIP). . In addition, superposition | stacking and lamination | stacking are arbitrary processes.

[Preparation of shrinkage suppression layer]
A slurry was prepared by adding a dispersant to commercially available alumina particles (average particle size: 1.0 μm) in an acrylic resin dispersed in water and stirring for 48 hours with a ball mill. The content of alumina in this slurry was 70.0% by mass, and the content of acrylic resin was 12.5% by mass. The slurry was molded to a thickness of 100 μm on a PET film that had been subjected to a release treatment by the doctor blade method, and was subjected to primary drying at 80 ° C. and secondary drying at 95 ° C. to obtain a sheet-like material. . As a preparatory body for the shrinkage suppression layer, two sheet-like materials after peeling the PET film are superposed and pressurized at 196.1 MPa for 10 minutes using an isotropic pressure device (CIP). A dense green sheet was produced. In addition, superposition | stacking and lamination | stacking are arbitrary processes.

[Production of laminate]
The produced green sheets are superposed in the order of alumina / negative electrode / solid electrolyte / positive electrode / alumina, and are laminated by applying pressure at 196.1 MPa for 10 minutes using an isotropic pressure device (CIP). The body was made.

[Baking]
The laminate was heated at 480 ° C. for 2 hours (degreasing), then rapidly heated to 900 ° C. and held at 900 ° C. for 3 minutes (sintering). Thereafter, the laminate was rapidly cooled to 600 ° C., held at 600 ° C. for 10 minutes, and then gradually cooled to room temperature to obtain a sintered laminate. Alumina was removed from the sintered laminate and ultrasonic cleaning was performed, followed by drying at 90 ° C. in an atmosphere with a dew point of −60 ° C. The area of the main surface of the sintered laminate obtained here was 97.7% of the laminate before firing, and the area shrinkage rate was 2.3%.

  Then, an aluminum paste is applied on the positive electrode layer, dried and fired, a current collector is attached to the positive electrode side, a copper paste is applied on the negative electrode layer, dried and fired, and the negative electrode side A current collector was attached.

  Then, an aluminum foil is connected to the positive electrode as a positive electrode lead, a copper foil is connected to the negative electrode as a negative electrode lead, and this connection body is sealed in an aluminum laminate film whose inner surface is insulation-coated to produce a lithium battery. did. This lithium battery was a secondary battery that was discharged at an average voltage of 2.5 V and was chargeable / dischargeable.

[Production of laminate]
A laminate was prepared in the same procedure as in Example 1 except that the negative electrode green sheet was not used and the layers were superimposed in the order of alumina / solid electrolyte / positive electrode / alumina.

[Baking]
The laminate was heated at 480 ° C. for 2 hours (degreasing), then rapidly heated to 900 ° C. and held at 900 ° C. for 3 minutes (sintering). Thereafter, the laminate was rapidly cooled to 600 ° C., held at 600 ° C. for 10 minutes, and then gradually cooled to room temperature to obtain a sintered laminate. Alumina was removed from the sintered laminate and ultrasonic cleaning was performed, followed by drying at 90 ° C. in an atmosphere with a dew point of −60 ° C. The area of the main surface of the sintered laminate obtained here was 98.8% of the laminate before firing, and the area shrinkage rate was 1.2%.

  Thereafter, an aluminum paste was applied on the positive electrode layer, dried and baked to attach a current collector on the positive electrode side.

On the other hand, a polymer of polyethylene oxide and polypropylene oxide and LiTFSI were added to acetonitrile, and dissolved by stirring for 24 hours using a biaxial mixer. This paste is molded to a thickness of 1 μm on a PET film that has been subjected to a release treatment by the doctor blade method, subjected to primary drying at 70 ° C., secondary drying at 80 ° C., and 25 ° C. in an atmosphere with a dew point of −60 ° C. A thin film was obtained by performing tertiary drying. The ionic conductivity of this thin film was 5.5 × 10 ⁻⁵ Scm ⁻¹ . The thin film was attached to the surface of the solid electrolyte layer opposite to the positive electrode layer, and a lithium metal film having a thickness of 100 μm was further attached to form a negative electrode.

  Then, an aluminum foil is connected to the positive electrode as a positive electrode lead, a copper foil is connected to the negative electrode as a negative electrode lead, and this connection body is sealed in an aluminum laminate film whose inner surface is insulation-coated to produce a lithium battery. did. This lithium battery was a secondary battery that was discharged at an average voltage of 3.6 V and was chargeable / dischargeable.

[Production of laminate]
The solid electrolyte sheet produced in Example 1 was baked at 900 ° C. for 3 minutes to obtain a solid electrolyte substrate (ion conductivity 1.5 × 10 ⁻⁴ Scm ⁻¹ ). Acetone is sprayed on the solid electrolyte substrate, the positive electrode green sheet and the shrinkage suppression layer prepared in Example 1 are superimposed, and a heating press in which an elastic body is installed on the upper surface of the press portion is used at 10 MPa for 10 minutes. By pressurizing the laminate, a laminate in which each green sheet and the layer were bonded was produced.

[Baking]
The laminate was heated at 480 ° C. for 2 hours (degreasing), then rapidly heated to 900 ° C. and held at 900 ° C. for 3 minutes (sintering). Thereafter, the laminate was rapidly cooled to 600 ° C., held at 600 ° C. for 10 minutes, and then gradually cooled to room temperature to obtain a sintered laminate. Alumina was removed from the sintered laminate and ultrasonic cleaning was performed, followed by drying at 90 ° C. in an atmosphere with a dew point of −60 ° C. The area of the principal surface of the sintered laminate obtained here was 99.9% of the laminate before firing, and the area shrinkage rate was 0.1%.

It is a figure which shows the manufacture procedure of the lithium battery which concerns on one Embodiment of this invention. It is a figure which shows the manufacture procedure of the lithium battery which concerns on another embodiment of this invention.

Explanation of symbols

10, 10A Laminate 11 Solid electrolyte green sheet 13a Positive electrode green sheet (electrode green sheet)
13b Negative electrode green sheet (electrode green sheet)
15 Shrinkage suppression layer 21 Solid electrolyte layer 23a Positive electrode layer 23b, 23bA Negative electrode layer 40, 40A Lithium battery

Claims (14)

A solid electrolyte green sheet containing an oxide glass powder exhibiting lithium ion conductivity after heat treatment or a solid electrolyte layer having a lithium ion conductive crystal, and an electrode green sheet containing an active material that occludes and releases lithium ions. A method of manufacturing a lithium battery used,
Producing a laminate in which the electrode green sheet and a shrinkage suppression layer containing a powder of an inorganic substance having a melting point exceeding a predetermined temperature are sequentially laminated on at least one surface of the solid electrolyte green sheet or the solid electrolyte layer;
The manufacturing method of a lithium battery which has the procedure which bakes the said laminated body at the said predetermined temperature.   The method for producing a lithium battery according to claim 1, wherein an area shrinkage rate of the solid electrolyte green sheet or the electrode green sheet in firing is 10% or less.   The method for producing a lithium battery according to claim 1 or 2, wherein the thickness of the solid electrolyte green sheet is 50% or less of the thickness of the laminate.   The method for producing a lithium battery according to any one of claims 1 to 3, wherein a thickness of the shrinkage suppression layer is 10% or more of a thickness of the laminate.   The method for producing a lithium battery according to claim 1, wherein the inorganic substance has a melting point of 1100 ° C. or higher.   The method for producing a lithium battery according to claim 1, wherein the oxide glass powder has an average particle diameter of 5 μm or less.   The method for producing a lithium battery according to claim 1, wherein the maximum value of the particle diameter of the oxide glass powder is 20 μm or less.   The method for manufacturing a lithium battery according to claim 1, wherein the inorganic substance powder has an average particle diameter of 5 μm or less.   9. The method of manufacturing a lithium battery according to claim 1, wherein the maximum particle diameter of the inorganic substance powder is 20 μm or less.   The method for producing a lithium battery according to any one of claims 1 to 9, wherein the solid electrolyte green sheet or the solid electrolyte layer, the electrode green sheet, and the shrinkage suppression layer are laminated at a lamination pressure of 1 MPa or more. 11. The lithium battery according to claim 1, wherein the oxide glass powder has an ionic conductivity of 1 × 10 ⁻⁴ Scm ⁻¹ or more at 25 ° C. after heat treatment under the same conditions as the baking. Manufacturing method. The method for producing a lithium battery according to claim 1, wherein the solid electrolyte layer after firing has an ionic conductivity of 1 × 10 ⁻⁵ Scm ⁻¹ or more at 25 ° C. The powder of the oxide glass is Li _{1 + x + y} M _x (Ge _1-y Ti _y ) _2−x Si _z P _3−z O ₁₂ (wherein M is one or more selected from the group consisting of Al and Ga). The method for producing a lithium battery according to claim 1, further comprising a crystal represented by: 0 ≦ x ≦ 0.8, 0 ≦ y ≦ 1.0, and 0 ≦ z ≦ 0.6. The solid electrolyte after firing is expressed in mol%,
Li ₂ O: 12-18% and / or
_{Al 2 O 3 + Ga 2 O} 3: 5~10%, and / or,
_{TiO 2 + GeO 2: 35~45%} , and / or,
SiO ₂ : 1-10% and / or
P ₂ O _5: 30~40%
The method for producing a lithium battery according to any one of claims 1 to 13, comprising glass ceramics containing sodium.

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