JP5803700B2 - Inorganic all-solid secondary battery - Google Patents

Description

  The present invention relates to an inorganic all-solid secondary battery using lithium ions.

  In recent years, with the development of portable information devices such as personal computers and mobile phones, the demand for secondary batteries has increased rapidly. Conventionally, in such secondary batteries, as an ionic conduction medium (electrolyte), a liquid electrolyte (organic electrolyte) containing a flammable organic solvent or a gel polymer electrolyte in which a polymer is impregnated with an organic electrolyte is mainly used. It is used. Such secondary batteries have problems such as electrolyte leakage.

  In response to this problem, an inorganic all-solid secondary battery in which an inorganic solid electrolyte is used as an electrolyte and all other elements are made of solid is being developed. An inorganic all-solid secondary battery has extremely high safety because there is no risk of leakage. In particular, inorganic all-solid-state lithium ion secondary batteries are being researched as secondary batteries that can easily achieve a high energy density. A conventional inorganic all solid state secondary battery has been manufactured by the following procedure (see Patent Documents 1 and 2).

  First, a solid electrolyte green sheet containing an inorganic solid electrolyte powder and an organic binder, and an electrode green sheet containing a positive or negative active material powder and an organic binder are prepared. Next, a solid electrolyte green sheet is laminated so as to be sandwiched between electrode positive and negative electrode green sheets, and this is fired. The added organic binder can volatilize during firing. A current collector layer of each polarity is formed on the fired positive electrode layer and negative electrode layer to obtain an inorganic all-solid secondary battery.

  However, when each green sheet shrinks when exposed to a high temperature atmosphere during firing, there is generally a large difference in shrinkage between the electrode green sheet and the solid electrolyte green sheet. For this reason, the laminated body after baking has the problem that defects, such as curvature, peeling, and a crack, generate | occur | produce.

  To solve this problem, there is a technology that prepares an inorganic substance powder having a melting point higher than the firing temperature of the laminate, and arranges a layer containing this powder outside the laminate, thereby suppressing shrinkage during firing. It has been proposed (see Patent Document 3). It is said that this battery manufacturing method can alleviate problems caused by differences in the shrinkage rates of the members in the sintering of the laminate. However, since the shrinkage of the laminate is actually an isometric phenomenon, the shrinkage phenomenon necessary for densifying the laminate and mechanically strengthening the laminate is also suppressed. As a result, sufficient densification is difficult at the time of firing, and there is a tendency that practically sufficient density and bending strength cannot be obtained in an inorganic all-solid secondary battery. For this reason, there is a problem that problems such as warping, peeling and cracking of the inorganic all solid state secondary battery cannot be sufficiently solved, and it cannot be said that a practically sufficient inorganic all solid state secondary battery has been realized.

JP 2007-5279 A JP 2007-227362 A JP 2009-181882 A

  The present invention has been made in view of such problems, and proposes a structure of an inorganic all-solid secondary battery having a practically sufficient density and bending strength at the same time. Here, it is considered that the inorganic all-solid secondary battery has a density of 85% or more from the viewpoint of volume capacity and a bending strength of 200 MPa or more from the viewpoint of mechanical characteristics, as practically necessary characteristics. ing. An object of the present invention is to provide an inorganic all solid state secondary battery having a structure in which cracks and peeling do not occur by achieving these characteristics.

In order to solve the problem, the structure of the inorganic all-solid secondary battery according to the present invention is as follows.
(1) Li _{1 + x} AlxGe _2-x (PO ₄ ) ₃ (wherein x is 0 ≦ x ≦ 1, which is a lithium ion conductive crystallized glass material. Hereinafter, this crystallized glass material is referred to as “LAGP crystal”. A solid electrolyte layer that is a composite containing a lithium ion conductive inorganic solid electrolyte,
(2) a positive electrode layer that is a composite containing LAGP crystallized glass and a positive electrode active material;
(3) a negative electrode layer that is a composite containing LAGP crystallized glass and a negative electrode active material;
In the battery element body, each of the solid electrolyte layer, the positive electrode layer, and the negative electrode layer has a structure containing 10 mass% or more and 95 mass% or less of LAGP crystallized glass. Here, the “lithium ion conductive inorganic solid electrolyte” refers to an inorganic solid material having a lithium ion conductivity of 1 × 10 ⁻⁸ Scm ⁻¹ or more at 25 ° C.

  By making the inorganic all-solid secondary battery the structure of the present invention, it was difficult to realize in a conventional inorganic all-solid secondary battery, a practically sufficient density of 85% by volume or more and a bending strength of 200 MPa or more. Can be realized simultaneously. The LAGP crystallized glass is filled in the voids of each layer in the inorganic all-solid secondary battery to improve the density. When LAGP crystallized glass is added in an amount of 10% by mass or more and 95% by mass or less, a density of 85% or more can be realized for the inorganic all-solid secondary battery. On the other hand, LAGP crystallized glass has a high strength because it has a large number of fine grain boundaries / slip planes, and the all-solid-state secondary battery to which LAGP crystallized glass is added in the above range has a bending strength of 200 MPa or more. Can be obtained. In addition, since LAGP crystallized glass has high lithium ion conductivity including a grain boundary, these effects do not impair the charge / discharge characteristics of the inorganic all-solid secondary battery.

  By obtaining a practically sufficient density and bending strength according to the present invention, the inorganic all-solid secondary battery simultaneously achieves the effect of preventing the occurrence of defects such as warpage, peeling, and cracking of the laminate after firing. I can do it.

FIG. 1 is a diagram schematically showing the structure of an inorganic all solid state secondary battery according to an embodiment of the present invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the embodiment described below is merely an example of an embodiment for carrying out the present invention, and the technical idea of the present invention is not limited to the following embodiment.

(Inorganic all-solid secondary battery)
FIG. 1 is a schematic cross-sectional view of an inorganic all solid state secondary battery which is a preferred embodiment of the present invention. An inorganic all solid state secondary battery according to an embodiment of the present invention,
(1) Solid electrolyte layer 1 which is a composite composed of LAGP crystallized glass 11 and a ceramic solid which is a lithium ion conductive inorganic solid electrolyte 12;
(2) positive electrode layer 2 that is a composite containing LAGP crystallized glass 11 and ceramic solid that is positive electrode active material 21;
(3) negative electrode layer 3 which is a composite containing LAGP crystallized glass 11 and a ceramic solid which is negative electrode active material 31;
It is an inorganic all solid secondary battery formed by stacking. The inorganic all-solid secondary battery includes a plate-shaped solid electrolyte layer 1, a positive electrode layer 2 formed by firing and integration on one surface of the solid electrolyte layer, and a fired integration on the other surface of the solid electrolyte layer 1. The first current collector layer 4 electrically connected to the positive electrode layer 2, and the second current collector layer 5 electrically connected to the negative electrode layer 3. Is preferred. Furthermore, it is preferable to provide leads 7 and 8 on the current collector layers 4 and 5 in order to output electricity to the outside.

  The “composite” according to the embodiment indicates, for example, a mixed structure including at least two phases of a LAGP crystallized glass and a ceramic solid. Alternatively, or as a non-uniform structure of a phase derived from the LAGP amorphous glass raw material and a phase derived from the ceramic solid raw material.

  The “crystallized glass” according to the embodiment is obtained by crystallizing part or all of the amorphous glass under the firing conditions according to one embodiment of the present invention. A crystal material (glass ceramic) having a crystal amount (crystallinity) of 100% by mass is also included.

The ceramic solid according to the embodiment is a material having a sintering temperature higher than the sintering temperature of “crystallized glass”, and does not substantially sinter under the firing condition according to an embodiment of the present invention. Material. In addition to the above-mentioned “ceramic solid that is the lithium ion conductive inorganic solid electrolyte 12”, “ceramic solid that is the positive electrode active material 21”, and “ceramic solid that is the negative electrode active material 31”, as necessary It contains a conductive auxiliary agent (for example, carbon powder, metal powder such as aluminum, conductive oxide powder such as SnO ₂ , etc.) and other fillers (eg alumina powder, etc.).

  The solid electrolyte layer 1 according to the embodiment is a composite composed of a lithium ion conductive inorganic solid electrolyte LAGP crystallized glass 11 and a ceramic solid that is a lithium ion conductive inorganic solid electrolyte 12, and LAGP crystallized glass. 11 is contained in an amount of 10% by mass to 95% by mass.

  Although there is no restriction | limiting in particular in the thickness of the solid electrolyte layer 1, Preferably they are 5 micrometers-1 mm, More preferably, they are 5 micrometers-100 micrometers.

There is no restriction | limiting in particular about the kind of solid electrolyte 12, A conventionally well-known solid electrolyte can be used. For example, Li _7-x La ₃ (Zr _2-x , A _x ) O ₁₂ (wherein A is one or more elements selected from the group consisting of Ti, Al, Si, Ge, V, and Y, x is 0 <x ≦ 0.3), La _{2 / 3-x} Li _3x TiO ₃ (wherein x is 0.04 ≦ x ≦ 0.15), and the like. It is also possible to use mixtures of such materials.

  The positive electrode layer 2 according to the embodiment is a composite containing a positive electrode active material 21 that occludes and releases lithium ions, LAGP crystallized glass 11, and a conductive additive. The mixing ratio of the conductive aid in the composite is preferably 35% by mass or less.

There is no restriction | limiting in particular in the kind of positive electrode active material 21, A conventionally well-known positive electrode active material can be used. For example, those containing lithium as a mobile ion can be suitably used, and LiVOPO ₄ , LiCoO ₂ , LiCoPO ₄ , LiNiO ₂ , LiMn ₂ O ₄ , LiFePO ₄ , LixV ₂ O ₅ (where 0.28 ≦ x ≦ 0.76) and the like. In particular, LiVOPO ₄ is preferable in terms of compatibility with the LAGP crystallized glass 11 because it can be obtained as crystallized glass if the raw material powder is appropriately selected.

There is no restriction | limiting in particular in the kind of conductive support agent, A conventionally well-known electronic conductive material can be used for a conductive support agent. In particular, those using lithium as a movable ion can be preferably used. For example, graphite, amorphous carbon, NiO, TiO ₂ , SnO _{2 and the} like can be mentioned.

  Although there is no restriction | limiting in particular in the thickness of the positive electrode layer 2, Preferably they are 5 micrometers-1 mm, More preferably, they are 5 micrometers-100 micrometers.

  The negative electrode layer 3 according to the embodiment is a composite containing a negative electrode active material 31 that occludes and releases lithium ions, and also contains both the LAGP crystallized glass 11 and a conductive additive. Moreover, it is preferable that the mixture ratio of the conductive support agent in a composite is 35 mass% or less.

There is no restriction | limiting in particular in the kind of the negative electrode active material 31, The conventionally well-known substance which uses lithium as a movable ion can be used suitably. For _example, can be mentioned _{Li 4 Ti 5 O 12, P} 2 O 5 -SnO -based _glass, a SnO 2, TiO ₂ or the like.

  Although there is no restriction | limiting in particular in the thickness of the negative electrode layer 3, Preferably it is 5 micrometers-1 mm, More preferably, it is 5 micrometers-100 micrometers.

  The battery element of the inorganic all-solid-state secondary battery according to an embodiment of the present invention uses a green sheet prepared for each of the solid electrolyte layer 1, the positive electrode layer 2, and the negative electrode layer 3 as a starting member. The “green sheet” in the present embodiment refers to an unfired body containing a LAGP amorphous glass powder and a ceramic solid powder formed into a thin plate shape, specifically, a LAGP amorphous glass powder and a ceramic solid powder. And a mixture slurry of an organic binder, a plasticizer, a solvent, and the like that can be volatilized during firing, into a thin plate shape. The molding can be performed by a doctor blade or calendar method, a coating method such as spin coating or dip coating, a printing method such as inkjet, bubble jet (registered trademark) and offset, a die coater method, or a spray method. Here, the “green sheet” includes a green sheet or a green sheet fired body coated with a mixed slurry.

  The content of the LAGP amorphous glass powder and the ceramic solid powder with respect to the dried green sheet is preferably 50% by mass or more, and more preferably 60% by mass or more. As a result, the voids after firing can be reduced, and a dense fired body having a density of 85% by volume or more and a bending strength of 200 MPa or more can be produced.

  The content of the LAGP amorphous glass powder is “mass of ceramic solid powder + mass of LAGP amorphous glass powder” in the solid electrolyte layer 1, the positive electrode layer 2, and the negative electrode layer 3 of the obtained inorganic all-solid secondary battery. On the other hand, it is 10 mass% or more and 95 mass% or less. At this time, it can be set as this numerical range about each layer of the solid electrolyte layer 1, the positive electrode layer 2, and the negative electrode layer 3 of an inorganic all-solid-state secondary battery by designing as content in the green sheet after drying. When the LAGP crystallized glass of the inorganic all-solid secondary battery is less than 10% by mass, it becomes difficult to obtain a practically sufficient density of 85% by volume or more and a bending strength of 200 MPa or more. When the LAGP crystallized glass exceeds 95% by mass, the occurrence of defects in the laminated body after firing, such as warpage of the laminated body, becomes remarkable due to the density exceeding 95% by volume. Since the organic binder and the solvent are scattered after firing, the plasticizer is reduced to a negligible level, so that the LAGP amorphous glass powder content can be ignored. Therefore, the content of the LAGP amorphous glass powder can be examined based on “mass of ceramic solid powder + mass of LAGP amorphous glass powder”.

  The content of the LAGP crystallized glass is more preferably 30% by mass or more and 80% by mass or less. In this case, the bending strength can be further increased by selecting the properties of the ceramic solid.

  The green sheet is preferably formed to have a uniform thickness so as to be uniformly heated during firing. 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 thickness distribution of the green sheet. Further, it is preferable that the raw materials are sufficiently mixed by a ball mill or the like to make the composition of the green sheet uniform, and uniaxially, isotropically pressurized or pressed by a roll press before being densified before firing.

  The green sheet of the solid electrolyte layer 1 is disposed between the green sheet of the positive electrode layer 2 and the green sheet of the negative electrode layer 3 to form a green sheet laminate. Thereafter, on the outer surface of the green sheet laminate (the side where the positive electrode layer 2 and the negative electrode layer 3 of the green sheet laminate do not face the solid electrolyte layer 1), a sheet shape that does not sinter at the firing temperature of the green sheet laminate. A support is formed to obtain a laminate before firing. This pre-fired laminate is fired at a temperature equal to or higher than the firing temperature of the green sheet laminate and lower than the firing temperature of the sheet-like support to obtain a laminate. The non-sintered sheet-like support is removed from the fired laminate to obtain the inorganic all-solid secondary battery according to this embodiment.

The “sheet-like support” that does not sinter at the firing temperature of the laminate material is desirably a ceramic green sheet in which inorganic powder is dispersed in an organic binder that can volatilize during firing. Specifically, inorganic powders such as Al ₂ O ₃ , MgO, CaO, SiO ₂ , ZrO ₂ , BaO, and CeO ₂ can be used. For example, the oxide inorganic powder is volatilized during firing of the unsintered ceramic body. A ceramic green sheet obtained by dispersing in an organic binder and molding it into a sheet can be suitably used.

  The green sheet laminate can be laminated at a predetermined lamination pressure after all the green sheets or layers are superimposed. The lamination pressure is preferably in the range of 1 MPa to 1000 MPa.

  The green sheet laminate is preferably fired while exchanging air in a gas furnace, microwave furnace, electric furnace or the like. And after baking, the sheet-like support body which does not sinter which remain | survives as an unsintered body on both surfaces of a laminated body is removed, and the sintered laminated body can be obtained.

  Then, current collector layers 4 and 5 are formed on the positive electrode layer 2 and the negative electrode layer 3 of the laminated body after sintering. For example, a current collector paste containing current collector powder, an organic binder, and the like is applied to the positive electrode layer 2 and the negative electrode layer 3, and the applied product is baked. Specific examples include at least one selected from the group consisting of aluminum, copper, nickel, palladium, silver, gold, and platinum. Alternatively, the current collector layers 4 and 5 may be formed by a thin film forming method such as a vapor deposition method or a sputtering method.

  Thereafter, in order to output electricity to the outside, the current collector layers 4 and 5 are provided with leads 7 and 8, and an inorganic all-solid secondary battery can be manufactured. For the leads 7 and 8, a known member such as a low-resistance metal material such as aluminum or nickel can be appropriately used.

  The fine density means “100 (volume%) − porosity (volume%)”, and “porosity (volume%)” means that the cross-sectional polished surface of the fired laminate is scanned with a scanning electron. The average value of values obtained by measuring 20 or more pore area ratios observed in a 50 μm vertical and horizontal plane when observed with a microscope (SEM). By increasing the number of measurements, it can be approximated to the porosity of the entire laminate after firing.

  Further, the bending strength can be measured by a three-point bending measurement method stipulated in JIS R 1601 for a laminated body after sintering before forming a current collector layer.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

(Example 1)
(Preparation of inorganic solid electrolyte amorphous glass powder)
First, by a solid phase reaction method in which powders of Li ₂ CO ₃ , GeO ₂ , Al ₂ O ₃ and NH ₄ H ₂ (PO ₄ ) ₃ are pulverized and mixed with a stoichiometric composition and fired at 900 ° C. in the atmosphere. Crystal powder of inorganic solid electrolyte material Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ was obtained.

The obtained Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ crystal powder was put into a Pt crucible, put into an atmospheric furnace heated to 1200 ° C., held for 1 hour, taken out, and rapidly cooled with ice water Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ obtained by vitrification was obtained. This was pulverized with a mortar and a ball mill to obtain a finely divided LAGP amorphous glass powder.

(Adjustment of solid ceramic body powder)
First, powders of Li ₂ CO ₃ , La (OH) ₃ , ZrO ₂ , and Al ₂ O ₃ were pulverized and mixed with a stoichiometric composition, and calcined in the atmosphere at 950 ° C. for 10 hours. Thereafter, the powder calcined for the purpose of compensating for the loss of Li in the main sintering was 10 at. Li ₂ CO ₃ was excessively added so as to be a%. This powder was mixed, molded, and then sintered in the atmosphere at 1200 ° C. for 36 hours to obtain Li _6.75 La ₃ (Zr _1.75 Al _0.25 ) O ₁₂ (hereinafter, , "LLZ crystal powder"). This was pulverized with a mortar and a ball mill to obtain atomized LLZ crystal powder.

(Production of solid electrolyte green sheet)
LAGP amorphous glass powder and LLZ crystal powder have a mass ratio of 5: 5 (LAGP amorphous glass powder and ceramic solid powder have a mass ratio of 5: 5, that is, 50 mass% LAGP crystallized glass in the solid electrolyte layer) The release of the slurry obtained by mixing the mixed powder obtained by mixing at a mass ratio adjusted so as to be the content of), the acrylic ester copolymer as the organic binder, and the terpineol as the solvent. A solid electrolyte green sheet was obtained by forming a thin plate having a thickness of 30 μm on the applied PET film by a doctor blade method, performing primary drying at 80 ° C., and further performing secondary drying at 95 ° C.

(Adjustment of positive electrode active material powder)
First, powders of Li ₂ CO ₃ , V ₂ O ₅ and NH ₄ H ₂ (PO ₄ ) ₃ were pulverized and mixed with a stoichiometric composition, put into a Pt crucible, and put into an atmospheric furnace heated to 1300 ° C. After holding for 20 minutes, LiVOPO ₄ which was taken out and rapidly cooled with ice water and vitrified was obtained. This was pulverized with a mortar and ball mill to obtain a finely divided positive electrode active material powder.

(Preparation of positive electrode green sheet)
LAGP amorphous glass powder, positive electrode active material powder, and SnO ₂ powder are in a mass ratio of 5: 4: 1 (the mass ratio of LAGP amorphous glass powder to ceramic solid powder is 5: 5, that is, 50% by mass in the positive electrode layer) A mixed powder obtained by mixing at a mass ratio adjusted to be the content of the LAGP crystallized glass), a slurry obtained by mixing an acrylic ester copolymer as an organic binder and terpineol as a solvent, A positive electrode green sheet was obtained by forming a thin plate having a thickness of 50 μm on a PET film that had been subjected to a mold release treatment by a doctor blade method, followed by primary drying at 80 ° C. and secondary drying at 95 ° C. .

(Preparation of negative electrode green sheet)
LAGP amorphous glass powder, commercially available Li ₄ Ti ₅ O ₁₂ powder and SnO ₂ powder have a mass ratio of 5: 4: 1 (the mass ratio of LAGP amorphous glass powder to ceramic solid powder is 5: 5, that is, negative electrode Mixed powder obtained by mixing at a mass ratio adjusted so that the content of LAGP crystallized glass is 50% by mass), an acrylate copolymer as an organic binder, and terpineol as a solvent. The slurry obtained in this way is formed into a thin plate with a thickness of 50 μm by a doctor blade method on a PET film that has been subjected to a release treatment, and is primarily dried at 80 ° C., and further subjected to secondary drying at 95 ° C. A negative electrode green sheet was obtained.

(Preparation of green sheet of non-sintered sheet-like support)
A doctor blade on a PET film that has been subjected to a release treatment, a slurry obtained by mixing commercially available alumina powder (average particle size 1 μm), an acrylic ester copolymer as an organic binder, and terpineol as a solvent The green sheet was formed into a thin plate having a thickness of 50 μm by the above method, primarily dried at 80 ° C., and further subjected to secondary drying at 95 ° C. to obtain a support green sheet that was not sintered.

(Production of laminate)
The produced green sheets are superposed in the order of two support green sheets / two positive electrode green sheets / one solid electrolyte green sheet / two negative electrode green sheets / two support green sheets, and cold isostatically pressed. The laminated body was produced by pressurizing at 196.1 MPa for 10 minutes using an apparatus (CIP).

(Baking)
After heating (degreasing) the laminated body at 580 ° C. for 2 hours, the temperature was rapidly raised to 750 ° C., held at 750 ° C. for 30 minutes, and then gradually cooled to room temperature to obtain a sintered laminated body. After removing the alumina (support green sheet) from both surfaces of the sintered laminate by ultrasonic cleaning, drying was performed at 90 ° C. This obtained the laminated body which consists of a solid electrolyte layer, a positive electrode layer, and a negative electrode layer. At this time, at least a part of the LAGP amorphous glass powder was crystallized by this firing, and became LAGP crystallized glass.
That is, by this, a solid electrolyte layer which is a composite made of LAGP crystallized glass and a ceramic solid which is a lithium ion conductive inorganic solid electrolyte, and a positive electrode layer which is a composite containing LAGP crystallized glass and a positive electrode active material And the laminated body which consists of a negative electrode layer which is a composite containing LAGP crystallized glass and a negative electrode active material was obtained.

(Current collector layer formation)
By applying an aluminum paste on the positive electrode layer 2 of the sintered laminate, drying and firing, the current collector layer 4 is attached to the positive electrode layer 2, and a copper paste is applied on the negative electrode layer 3, The current collector layer 5 was attached to the negative electrode side by firing.

  Thereafter, an aluminum foil is connected to the positive electrode as the positive electrode lead 7, a copper foil is connected to the negative electrode as the negative electrode lead 8, and this connection body is sealed in an aluminum laminate film whose inner surface is insulation-coated. A solid secondary battery was produced. This inorganic all solid secondary battery was a secondary battery that was discharged at an average voltage of 2.5 V and could be charged.

(Example 2)
In the production of the solid electrolyte green sheet, the mass ratio of LAGP amorphous glass powder and solid ceramic body powder is 1: 9 (the mass ratio of LAGP amorphous glass powder and ceramic solid powder is 1: 9, that is, the solid electrolyte. The inorganic total solid of Example 2 was operated in the same manner as in Example 1 except that a mixed powder obtained by mixing at a mass ratio adjusted so that the content of LAGP crystallized glass was 10% by mass in the layer was used. A secondary battery was obtained.

(Example 3)
In the production of the positive electrode green sheet, the LAGP amorphous glass powder and the glass LiVOPO ₄ positive electrode active material powder and SnO ₂ powder were mixed at a mass ratio of 1: 8: 1 (LAGP amorphous glass powder and ceramic solid powder The mass ratio was 1: 9, that is, the same as in Example 1 except that the mixed powder obtained by mixing at a positive electrode layer was adjusted so that the content of LAGP crystallized glass was 10% by mass) was used. The inorganic all solid secondary battery of Example 3 was obtained.

Example 4
In the production of the negative electrode green sheet, the mass ratio of LAGP amorphous glass powder, Li ₄ Ti ₅ O ₁₂ powder and SnO ₂ powder was 1: 8: 1 (mass of LAGP amorphous glass powder and ceramic solid powder. The ratio was 1: 9, that is, the same operation as in Example 1 except that a mixed powder obtained by mixing the negative electrode layer with a mass ratio adjusted so that the content of LAGP crystallized glass was 10% by mass was used. Thus, an inorganic all solid secondary battery of Example 3 was obtained.

(Example 5)
Example 1 except that a solid electrolyte green sheet was produced in the same manner as in Example 2, a positive electrode green sheet was produced in the same manner as in Example 3, and a negative electrode green sheet was produced in the same manner as in Example 4. In the same manner as in Example 5, an inorganic all-solid secondary battery of Example 5 was obtained.

(Example 6)
In the production of the solid electrolyte green sheet, the LAGP amorphous glass powder and the solid ceramic body powder have a mass ratio of 3: 7 (the mass ratio of the LAGP amorphous glass powder and the ceramic solid powder is 3: 7, that is, the solid electrolyte. The inorganic total solid of Example 2 was operated in the same manner as in Example 1 except that a mixed powder obtained by mixing at a mass ratio adjusted so that the content of LAGP crystallized glass was 30% by mass in the layer was used. A secondary battery was obtained.

(Example 7)
At the time of producing the positive electrode green sheet, the LAGP amorphous glass powder and the LiVOPO ₄ positive electrode active material powder and SnO ₂ powder, which are glass, have a mass ratio of 3: 6: 1 (LAGP amorphous glass powder and ceramic solid powder The mass ratio was 3: 7, that is, the same as in Example 1 except that the mixed powder obtained by mixing at a mass ratio adjusted to have a content of LAGP crystallized glass of 30% by mass in the positive electrode layer was used. The inorganic all solid secondary battery of Example 3 was obtained.

(Example 8)
In the production of the negative electrode green sheet, the mass ratio of LAGP amorphous glass powder, Li ₄ Ti ₅ O ₁₂ powder, and SnO ₂ powder was 3: 6: 1 (mass of LAGP amorphous glass powder and ceramic solid powder. The ratio was 3: 7, that is, the same operation as in Example 1 except that a mixed powder obtained by mixing at a negative electrode layer was mixed at a mass ratio adjusted to a content of LAGP crystallized glass of 30% by mass). Thus, an inorganic all solid secondary battery of Example 3 was obtained.

Example 9
Example 1 except that a solid electrolyte green sheet was produced in the same manner as in Example 6, a positive electrode green sheet was produced in the same manner as in Example 7, and a negative electrode green sheet was produced in the same manner as in Example 8. In the same manner as in Example 9, an inorganic all-solid secondary battery of Example 9 was obtained.

(Example 10)
In the production of the solid electrolyte green sheet, the mass ratio of LAGP amorphous glass powder and solid ceramic body powder is 8: 2 (the mass ratio of LAGP amorphous glass powder and ceramic solid powder is 8: 2, that is, solid electrolyte. The inorganic total solid of Example 10 was operated in the same manner as in Example 1 except that a mixed powder obtained by mixing at a mass ratio adjusted so that the content of LAGP crystallized glass was 80% by mass in the layer was used. A secondary battery was obtained.

(Example 11)
In the production of the positive electrode green sheet, the mass ratio of LAGP amorphous glass powder and LiVOPO ₄ positive electrode active material powder, which is glass, and SnO ₂ powder is 8: 1.5: 0.5 (LAGP amorphous glass powder and The mass ratio with the ceramic solid powder was 8: 2, that is, the mixed powder obtained by mixing with the positive electrode layer was adjusted so that the content of the LAGP crystallized glass was 80% by mass). An inorganic all solid secondary battery of Example 11 was obtained by operating in the same manner as in Example 1.

(Example 12)
In the production of the negative electrode green sheet, LAGP amorphous glass powder, Li ₄ Ti ₅ O ₁₂ powder and SnO ₂ powder were mixed at a mass ratio of 8: 1.5: 0.5 (LAGP amorphous glass powder and ceramic solid). Example 1 except that a mixed powder obtained by mixing at a mass ratio of 8: 2 with the powder, that is, a mass ratio adjusted so that the negative electrode layer has a content of LAGP crystallized glass of 80% by mass) was used. An inorganic all solid secondary battery of Example 12 was obtained in the same manner as described above.

(Example 13)
Example 1 except that a solid electrolyte green sheet was produced in the same manner as in Example 10, a positive electrode green sheet was produced in the same manner as in Example 11, and a negative electrode green sheet was produced in the same manner as in Example 12. An inorganic all solid secondary battery of Example 13 was obtained in the same manner as described above.

(Example 14)
In the production of the solid electrolyte green sheet, the mass ratio of LAGP amorphous glass powder and solid ceramic body powder is 9: 1 (the mass ratio of LAGP amorphous glass powder and ceramic solid powder is 9: 1, that is, solid electrolyte. The inorganic all solids of Example 14 were operated in the same manner as in Example 1 except that a mixed powder obtained by mixing at a mass ratio adjusted so that the content of LAGP crystallized glass was 90% by mass in the layer was used. A secondary battery was obtained.

(Example 15)
In the production of the positive electrode green sheet, the mass ratio of LAGP amorphous glass powder, LiVOPO ₄ positive electrode active material powder and SnO ₂ powder, which is glass, is 9: 0.7: 0.3 (LAGP amorphous glass powder and The mass ratio with the ceramic solid powder was 9: 1, that is, the mixed powder obtained by mixing at a mass ratio adjusted so that the content of the LAGP crystallized glass was 90% by mass in the positive electrode layer was used. An inorganic all solid secondary battery of Example 15 was obtained by operating in the same manner as in Example 1.

(Example 16)
In the production of the negative electrode green sheet, the mass ratio of LAGP amorphous glass powder, Li ₄ Ti ₅ O ₁₂ powder and SnO ₂ powder was 9: 0.7: 0.3 (LAGP amorphous glass powder and ceramic solid Example 1 except that a mixed powder obtained by mixing at a mass ratio of 9: 1 with the powder, that is, a mass ratio adjusted so that the content of the LAGP crystallized glass was 90% by mass in the negative electrode layer was used. In the same manner as in Example 16, an inorganic all solid secondary battery of Example 16 was obtained.

(Example 17)
Example 1 except that a solid electrolyte green sheet was produced in the same manner as in Example 14, a positive electrode green sheet was produced in the same manner as in Example 15, and a negative electrode green sheet was produced in the same manner as in Example 16. An inorganic all solid secondary battery of Example 17 was obtained in the same manner as described above.

(Comparative Example 1)
In the production of the solid electrolyte green sheet, the mass ratio of LAGP amorphous glass powder and solid ceramic body powder is 0.9: 9.1 (the mass ratio of LAGP amorphous glass powder and ceramic solid powder is 0.9). : 9.1, that is, the same operation as in Example 1 except that a mixed powder obtained by mixing the solid electrolyte layer at a mass ratio adjusted so that the content of LAGP crystallized glass is 9% by mass is used. Thus, an inorganic all solid secondary battery of Comparative Example 1 was obtained.

(Comparative Example 2)
In the production of the positive electrode green sheet, the mass ratio of LAGP amorphous glass powder, LiVOPO ₄ positive electrode active material powder, which is glass, and SnO ₂ powder is 0.9: 8: 1.1 (LAGP amorphous glass powder and The mass ratio with the ceramic solid powder is 0.9: 9.1, that is, a mixed powder obtained by mixing at a positive electrode layer adjusted so that the content of LAGP crystallized glass is 9 mass%) is used. An inorganic all solid secondary battery of Comparative Example 2 was obtained by operating in the same manner as in Example 1 except that.

(Comparative Example 3)
In the production of the negative electrode green sheet, the mass ratio of LAGP amorphous glass powder, Li ₄ Ti ₅ O ₁₂ powder and SnO ₂ powder was 0.9: 8: 1.1 (LAGP amorphous glass powder and ceramic solid The mass ratio with the powder is 0.9: 9.1, that is, the mixed powder obtained by mixing the negative electrode layer with a mass ratio adjusted so that the content of LAGP crystallized glass is 9% by mass) is used. Were operated in the same manner as in Example 1 to obtain an inorganic all solid secondary battery of Comparative Example 3.

(Comparative Example 4)
Example 1 except that a solid electrolyte green sheet was prepared by the same method as Comparative Example 1, a positive electrode green sheet was prepared by the same method as Comparative Example 2, and a negative electrode green sheet was prepared by the same method as Comparative Example 3. An inorganic all solid secondary battery of Comparative Example 4 was obtained in the same manner as described above.

(Comparative Example 5)
In the production of the solid electrolyte green sheet, the mass ratio of LAGP amorphous glass powder and solid ceramic body powder is 9.6: 0.4 (the mass ratio of LAGP amorphous glass powder and ceramic solid powder is 9.6). : 0.4, that is, the same operation as in Example 1 except that a mixed powder obtained by mixing at a solid electrolyte layer with a mass ratio adjusted to 96 mass% LAGP crystallized glass) was used. Thus, an inorganic all solid secondary battery of Comparative Example 5 was obtained.

(Comparative Example 6)
At the time of producing the positive electrode green sheet, the mass ratio of LAGP amorphous glass powder, LiVOPO ₄ positive electrode active material powder, which is glass, and SnO ₂ powder is 9.6: 0.3: 0.1 (LAGP amorphous glass powder and The mass ratio with the ceramic solid powder is 9.6: 0.4, that is, a mixed powder obtained by mixing at a positive electrode layer adjusted so that the content of the 96 mass% LAGP crystallized glass is obtained. Except for the above, an inorganic all solid secondary battery of Comparative Example 6 was obtained in the same manner as in Example 1.

(Comparative Example 7)
In the production of the negative electrode green sheet, the mass ratio of LAGP amorphous glass powder, Li ₄ Ti ₅ O ₁₂ powder and SnO ₂ powder was 9.6: 0.3: 0.1 (LAGP amorphous glass powder and ceramic The mass ratio with the solid powder is 9.6: 0.4, that is, the mixed powder obtained by mixing at a mass ratio adjusted so that the negative electrode layer has a content of 96 mass% LAGP crystallized glass is used. Except that, an inorganic all solid secondary battery of Comparative Example 7 was obtained in the same manner as in Example 1.

(Comparative Example 8)
Example 1 except that a solid electrolyte green sheet was prepared by the same method as Comparative Example 5, a positive electrode green sheet was prepared by the same method as Comparative Example 6, and a negative electrode green sheet was prepared by the same method as Comparative Example 7. In the same manner as in Example 1, an inorganic all solid secondary battery of Comparative Example 8 was obtained.

(Evaluation)
The inorganic all solid state secondary batteries obtained in Examples 1 to 17 and Comparative Examples 1 to 8 were processed at the stage of the sintered laminate before forming the current collector layer, with the following methods: density, bending strength, warpage, Evaluation of crack and peeling was performed on 10 substrates of each level. The evaluation results obtained are summarized in Table 1. “Density” was obtained as the average pore area ratio for each level from the results of SEM observation (50 μm in length and width) performed on each substrate at each level. “Folding strength” was performed in accordance with the measurement of bending strength specified in the three-point bending measurement method of JIS R 1601. In addition, “warp” is a result of evaluation with a laminate after sintering before forming a current collector layer. When the substrate surface is measured with a contact-type surface roughness meter, the outer periphery relative to the horizontal plane at the center of the substrate The displacement of the part was measured. Regarding “cracking and peeling”, the laminate after sintering was visually observed, and expressed as “number of cracks and peeling occurred / total number of substrates (10)”.

  As shown in Table 1, it was confirmed that the inorganic all-solid secondary batteries of Examples 1 to 17 had practically sufficient density and bending strength at the same time. On the other hand, it was confirmed that the inorganic all solid state secondary batteries of Comparative Examples 1 to 8 did not reach a practical level in both density and bending strength. Thereby, while the inorganic all solid state secondary batteries of Examples 1 to 17 are suppressed from occurrence of cracks or peeling defects, the inorganic all solid state secondary batteries of Comparative Examples 1 to 8 are warped and cracked. It was recognized that the occurrence of any defect in peeling was significant. From these results, it was confirmed that the inorganic all solid state secondary battery according to the practice of the present invention is at a practical level as exemplified in Examples 1 to 17.

  The present invention provides an inorganic all-solid secondary battery that has a practically sufficient density and bending strength and is free from defects such as cracks and peeling, and thus can be used industrially.

  DESCRIPTION OF SYMBOLS 1 ... Solid electrolyte layer, 11 ... LAGP crystallized glass, 12 ... Inorganic solid electrolyte of lithium ion conductivity, 2 ... Positive electrode layer, 21 ... Positive electrode active material, 3 ... Negative electrode Layer, 31 ... negative electrode active material, 4 ... first current collector layer, 5 ... second current collector layer, 7 ... positive electrode lead, 8 ... negative electrode lead

Claims (1)

Li ₁ + _x Al _x Ge _2-x (PO ₄ ) ₃ crystallized glass (wherein x is 0 ≦ x ≦ 1 (hereinafter referred to as “LAGP crystallized glass”)) and lithium ions A solid electrolyte layer that is a composite composed of a ceramic solid that is a conductive inorganic solid electrolyte; and
A positive electrode layer that is a composite containing LAGP crystallized glass and a positive electrode active material;
A laminate of a negative electrode layer which is a composite containing LAGP crystallized glass and a negative electrode active material;
An inorganic all solid secondary battery, wherein each of the solid electrolyte layer, the positive electrode layer, and the negative electrode layer is made of a sintered body containing LAGP crystallized glass of 10% by mass to 95% by mass.

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