JP2020149782A - All-solid battery - Google Patents

Abstract

To provide an all-solid battery having high I/O characteristics.SOLUTION: An all-solid battery 1 comprises: a laminate where multiple electrode layers by laminating collector layers 31, 41 and active material layers 32, 42, are laminated via a solid electrolyte layer 50; and a boundary surface of the solid electrolyte layer 50 and the active material layers 32, 42, where the active material layers 32, 42 contain Ti and V. When defining the same direction as the lamination direction, and directing from the boundary surface toward the collector layers 31, 41 closest thereto as the depth direction, formulas (1) and (2) are satisfied. (R1-0.20d)≤R2≤(R1-0.15d) ... (1), 0.0<d≤3.0 ... (2) (d indicates the distance (μm) from the boundary surface in the depth direction, R1 represents the atomic weight ratio (Ti/(Ti+V)) of Ti and V in the active material layers 32, 42, at the boundary surface and R2 represents the atomic weight ratio (Ti/(Ti+V)) of Ti and V in the collector layers 31, 41 at a point d).SELECTED DRAWING: Figure 1

Description

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

In recent years, the development of electronics technology has been remarkable, and portable electronic devices have been made smaller and lighter, thinner, and more multifunctional. Along with this, there is a strong demand for batteries that serve as power sources for electronic devices to be smaller and lighter, thinner, and more reliable. Currently, in lithium ion secondary batteries that are widely used, an electrolyte (electrolyte solution) such as an organic solvent has been conventionally used as a medium for moving ions. However, in the battery having the above configuration, there is a risk that the electrolytic solution may leak out. Further, since the organic solvent and the like used in the electrolytic solution are flammable substances, a battery with higher safety is required.

Therefore, as one measure for improving the safety of the battery, it has been proposed to use a solid electrolyte as an electrolyte instead of the electrolytic solution. Further, development of an all-solid-state battery in which a solid electrolyte is used as an electrolyte and other components are also composed of solids is underway. Here, in particular, in an all-solid-state battery using an oxide-based solid electrolyte, the contact property between solids is poor, the resistance is high, and it is difficult to increase the input / output.
Patent Documents 1 and 2 are disclosed with respect to increasing the input / output of an all-solid-state battery.
Patent Document 1 discloses an all-solid-state battery using a substance represented by a predetermined chemical formula, assuming that the low ionic conductivity of the solid electrolyte is caused by the low input / output. However, if only the substance described in Patent Document 1 is used, an unintended reaction may occur, the resistance may increase, and the input / output characteristics may decrease. Patent Document 2 discloses an all-solid-state battery capable of reducing resistance by forming an intermediate layer by reacting / diffusing a solid electrolyte and an electrode active material in order to strengthen the bonding at the interface between the electrode layer and the electrolyte layer. There is. Further, the electrolyte formed in the intermediate layer described in the examples of Patent Document 2 has low ionic conductivity, and it is considered difficult to increase the output by reducing the resistance.

JP-A-2007-258165 Patent No. 4797105

The present invention has been made in view of the above problems, and an object of the present invention is to provide an all-solid-state battery having high output / output characteristics.

The all-solid-state battery according to one aspect of the present invention includes a laminate in which a plurality of electrode layers in which a current collector layer and an active material layer are laminated are laminated via a solid electrolyte layer, and the solid electrolyte layer and the active material layer. The active material layer contains Ti and V, and is in the same direction as the stacking direction, and the direction from the interface toward the current collector layer closest to the interface is included. An all-solid-state battery that satisfies equations (1) and (2) when defined as the depth direction.
(R1-0.20d) ≤ R2 ≤ (R1-0.15d) ... (1)
0.0 <d ≤ 3.0 ... (2)
(D represents the distance (μm) from the interface in the depth direction, R1 represents the atomic weight ratio (Ti / (Ti + V)) of Ti and V in the active material layer at the interface, and R2 is. , X represents the atomic weight ratio of Ti to V in the active material layer (Ti / (Ti + V)).

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

It is an image cross-sectional view which shows the structure of the all-solid-state battery which concerns on one Embodiment of this disclosure. It is an enlarged view of the vicinity of the interface between the active material layer and the solid electrolyte layer in the region A of FIG. It is a graph for showing the relationship between the distance d and the atomic weight ratio of Ti and V in an active material in this embodiment.

Hereinafter, the invention will be described in detail with reference to the drawings as appropriate. The drawings used in the following description may be enlarged for convenience in order to make the features of the present invention easy to understand, and the dimensional ratios of the respective components may differ from the actual ones. is there. The materials, dimensions, etc. exemplified in the following description are examples, and the present invention is not limited thereto, and the present invention can be appropriately modified without changing the gist thereof.

As shown in FIGS. 1 and 2, the all-solid-state battery 1 includes a laminated body 20 in which a positive electrode 30 and a negative electrode 40 are laminated via a solid electrolyte layer 50. The positive electrode 30 has a positive electrode current collector layer 31 and a positive electrode active material layer 32. The negative electrode 40 has a negative electrode current collector layer 41 and a negative electrode active material layer 42. A margin layer 80 is formed on the same plane of the positive electrode 30 and the negative electrode 40. The laminated body 20 is a hexahedron, and has four side surfaces (first side surface 21, second side surface 22, third side surface 23, fourth side surface 24) formed as surfaces parallel to the stacking direction, and a stacking direction. It has an upper surface 25 and a lower surface 26 formed as surfaces orthogonal to. The positive electrode current collector layer 31 is exposed on the first side surface 21, and the negative electrode current collector layer 41 is exposed on the second side surface 22. The third side surface 23 is the side surface on the right side when viewed from the first side surface 21 side with the top surface 25 facing up, and the fourth side surface 24 is the side surface on the left side when viewed from the first side surface 21 side with the top surface 25 facing up. is there. Further, the first side surface 21 and the second side surface 22 face each other, and the third side surface 23 and the fourth side surface 24 face each other.

A positive electrode external electrode 60 that is electrically connected to the positive electrode current collector layer 31 is attached to the first side surface 21 of the laminated body. A negative electrode external electrode 70 that is electrically connected to the negative electrode current collector layer 41 is attached to the second side surface 22 of the laminated body 20.

In addition, as a description in the following specification, either one or both of the positive electrode active material and the negative electrode active material are collectively referred to as an active material, and either or both of the positive electrode active material layer 32 and the negative electrode active material layer 42 are referred to as active materials. Collectively, it is called an active material layer, and either or both of the positive electrode active current collector layer 31 and the negative electrode current collector layer 41 are collectively called a current collector layer, and either one or one of the positive electrode 30 and the negative electrode 40 or Both are collectively referred to as an electrode layer, and either or both of the positive electrode external electrode 60 and the negative electrode external electrode 70 may be collectively referred to as an external electrode. The materials used for the positive electrode active material layer 32 and the negative electrode active material layer 42 may be the same or different. The materials used for the positive electrode current collector layer 31 and the negative electrode current collector layer 32 may be the same or different.

The solid electrolyte layer 50 in the all-solid-state battery 1 according to the present embodiment contains titanium aluminum lithium phosphate, and the active material layer 3 contains vanadium lithium phosphate. The margin layer 80 contains titanium-aluminum-lithium phosphate. Of course, not limited to this, it is not necessary to use exactly the same material.

(Solid electrolyte)
The solid electrolyte layer 50 of the all-solid-state battery 1 of the present embodiment contains titanium aluminum lithium phosphate. Lithium aluminum hydride is preferably Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 0.6). Further, the solid electrolyte layer may contain a solid electrolyte material other than titanium-aluminum-lithium phosphate. For example, Li _{3 + x1} Si _x1 P _1-x1 O ₄ (0.4 ≤ x 1 ≤ 0.6), Li _3.4 V _0.4 Ge _0.6 O ₄ , Lithium germanium phosphate (LiGe ₂ (PO ₄ )). ₃ ), Li ₂ OV ₂ O _5- SiO ₂ , Li ₂ O-P ₂ O _5- B ₂ O ₃ , Li ₃ PO ₄ , Li _0.5 La _0.5 TiO ₃ , Li ₁₄ Zn (GeO ₄ ) _{4, Li 7 La 3 Zr 2} O 12, preferably includes a LiZr 2 _{(PO 4)} at least one member selected from the group consisting of _3.

(Active material)
As described above, the active material layer (positive electrode active material layer 32, negative electrode active material layer 42) of the all-solid-state battery 1 of the present embodiment contains lithium vanadium phosphate. Lithium vanadium phosphate includes LiVOPO ₄ , Li ₃ V ₂ (PO ₄ ) ₃ , Li ₂ VOP ₂ O ₇ , Li ₂ VP ₂ O ₇ , Li ₄ (VO) (PO ₄ ) ₂ , and Li ₉ V ₃ ( P ₂ O ₇ ) ₃ (PO ₄ ) ₂ is preferably one or more, and in particular, one or both of LiVOPO ₄ and Li ₃ V ₂ (PO ₄ ) ₃ . Furthermore, LiVOPO ₄ and Li ₃ V ₂ (PO ₄ ) ₃ preferably have a lithium deficiency, such as Li _x VOPO ₄ (0.94 ≤ x ≤ 0.98) and Li _x V ₂ (PO ₄ ) _3. It is more preferable if (2.8 ≦ x ≦ 2.95). Further, a part of V and P may be substituted with other elements Ca, Ti and Si.

The active material layer may contain an active material other than lithium vanadium phosphate. For example, it preferably contains a transition metal oxide and a transition metal composite oxide. Specifically, lithium manganese composite oxide Li ₂ Mn _x3 Ma _1-x3 O ₃ (0.8 ≤ x ₃ ≤ 1, Ma = Co, Ni), lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO _2). ), Lithium manganese spinel (LiMn ₂ O ₄ ), and general formula: LiNi _{x4 Coy4} Mn _z4 O ₂ (x4 + y4 + z4 = 1, 0 ≦ x4 ≦ 1, 0 ≦ y4 ≦ 1, 0 ≦ z4 ≦ 1). Composite metal oxide, lithium vanadium compound (LiV ₂ O ₅ ), olivine type LiMbPO ₄ (however, Mb is one or more selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr. elements), Li excess solid solution positive electrode _{Li 2 MnO 3 -LiMcO 2 (Mc} = Mn, Co, Ni), lithium titanate _{(Li 4 Ti 5 O 12)} , LiaNi x5 Co y5 Al z5 O 2 (0.9 It is preferably any of the composite metal oxides represented by <a <1.3, 0.9 <x5 + y5 + z5 <1.1). The content of these materials is preferably in the range of 1 part by mass to 20 parts by mass with respect to 100 parts by mass of lithium vanadium phosphate in the same active material layer.

Further, the active material layer contains at least Ti and V. The atomic weight ratio of these two elements may differ depending on the position of the active material layer near the interface between the solid electrolyte layer 50 and the active material layer and the position on the current collector side of the interface. Specifically, the atomic weight of Ti (Ti / (Ti + V)) contained in the active material layer may decrease from the interface 90 toward the nearest current collector layer.

Further, in the present embodiment, the following equation (1) is defined when the direction from the interface to the current collector layer closest to the interface 90 is defined as the depth direction DR1 in the same direction as the stacking direction. ) And (2) are preferably set.
(R1-0.20d) ≤ R2 ≤ (R1-0.15d) ... (1)
0.0 <d ≦ 3.0… (2)
(D indicates the distance (μm) from the interface 90 in the depth direction DR1.
R1 represents the atomic weight ratio (Ti / (Ti + V)) of Ti and V in the active material layer at the interface 90.
R2 represents the atomic weight ratio (Ti / (Ti + V)) of Ti and V in the active material layer at the point d. )

In other words, the atomic weight ratio of Ti and V in the active material layer at the point d of the active material layer in the present embodiment (where d is within the range of 0.0 <d ≦ 3.0) (Ti / (Ti + V)). ) R2 can be said to decrease toward DR1 in the depth direction within the range surrounded by R1-0.20d and R1-0.15d shown in FIG. The vertical axis of FIG. 3 represents the atomic weight ratio of Ti to V (Ti / (Ti + V)), and the horizontal axis represents the point at the distance d where (Ti / (Ti + V)) is measured.

By satisfying the equations (1) and (2), the potential difference applied to the vicinity of the interface 90 can be reduced to a suitable range, so that the interface resistance derived from the space charge layer can be reduced. As a result, the loss of lithium ions due to the formation of the space charge layer can be eliminated, the interfacial resistance can be reduced, and it is considered that excellent input / output characteristics can be obtained.

Here, the definition of the interface 90 between the solid electrolyte layer 50 and the active material layer will be described in detail. The interface 90 advances in the depth direction 90 when the atomic weight ratio of Ti and V (Ti / (Ti + V)) is measured every 1 μm in the depth direction 90 from an arbitrary position in the solid electrolyte layer 50. In the section where the atomic weight ratio of Ti to V (Ti / (Ti + V)) decreased by more than 0.1 per μm, the part closest to the solid electrolyte layer side (that is, the part farthest from the active material layer in the section). ).

(Positive current collector and negative electrode current collector)
As the material constituting the current collector layer (positive electrode current collector layer 31, negative electrode current collector layer 41) of the all-solid-state battery 1 of the present embodiment, it is preferable to use a material having a high conductivity, for example, silver or palladium. , Gold, platinum, aluminum, copper, nickel and the like are preferably used. In particular, copper is more preferable because it does not easily react with titanium aluminum lithium phosphate and has an effect of reducing the internal resistance of the all-solid-state battery.

Further, the current collector layer of the all-solid-state battery 1 of the present embodiment preferably contains an active material.

It is desirable that the current collector layer contains an active material because the adhesion between the current collector layer and the active material layer is improved.

The ratio of the active material in the current collector layer of the present embodiment is not particularly limited as long as it functions as a current collector, but the current collector and the active material are in the range of 90/10 to 70/30 in volume ratio. Is preferable.

(Margin layer)
The margin layer 80 of the all-solid-state battery of the present embodiment is preferably provided in order to eliminate a step between the solid electrolyte layer 50 and the electrode layer or the active material layer 3. Therefore, the margin layer 80 indicates a region other than the electrode or the active material layer. The presence of such a margin layer 80 eliminates a step between the solid electrolyte layer 50 and the electrode layer or the active material layer, so that the electrode layer becomes more dense and delamination due to firing of the all-solid-state battery 1. Lamination) and warpage are less likely to occur.

The material constituting the margin layer 80 preferably contains, for example, the same material as the solid electrolyte layer 50, titanium aluminum lithium phosphate. Therefore, the titanium-aluminum-lithium phosphate is preferably Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 0.6). Further, the margin layer 80 may contain a solid electrolyte material or an insulating oxide material other than titanium-aluminum-lithium phosphate. For example, Li _{3 + x1} Si _x1 P _1-x1 O ₄ (0.4 ≤ x 1 ≤ 0.6), Li _3.4 V _0.4 Ge _0.6 O ₄ , Lithium germanium phosphate (LiGe ₂ (PO ₄ )). ₃ ), Li ₂ OV ₂ O _5- SiO ₂ , Li ₂ O-P ₂ O _5- B ₂ O ₃ , Li ₃ PO ₄ , Li _0.5 La _0.5 TiO ₃ , Li ₁₄ Zn (GeO ₄ ) _4. It is preferable to contain at least one selected from the group consisting of Li ₇ La ₃ Zr ₂ O ₁₂ , Al ₂ O ₃ and ZrO ₂ .

(External electrode)
As the material of the external electrodes (positive electrode external electrode 61, negative electrode external electrode 71), it is preferable to use a material having a high conductivity. For example, silver, gold, platinum, aluminum, copper, tin and nickel can be used.

(Manufacturing method of all-solid-state battery)
The all-solid-state battery 1 of the present embodiment can be manufactured by the following procedure. Each material of the current collector layer, the active material layer, the solid electrolyte layer 50, and the margin layer 80 is made into a paste. The method of making a paste is not particularly limited, and for example, a paste can be obtained by mixing powders of the above materials with a vehicle. Here, vehicle is a general term for a medium in a liquid phase, and includes a solvent, a binder, and the like. The binder contained in the paste for forming the green sheet or the printing layer is not particularly limited, but polyvinyl acetal resin, cellulose resin, acrylic resin, urethane resin, vinyl acetate resin, polyvinyl alcohol resin and the like can be used. The slurry can contain at least one of the resins.

In addition, the paste may contain a plasticizer. The type of plasticizer is not particularly limited, but phthalates such as dioctyl phthalate and diisononyl phthalate may be used.

By such a method, a paste for a current collector layer, a paste for an active material layer, a paste for a solid electrolyte layer, and a paste for a margin layer are prepared.

The above-mentioned paste for a solid electrolyte layer is applied on a substrate such as polyethylene terephthalate (PET) to a desired thickness and dried if necessary to prepare a green sheet for a solid electrolyte. The method for producing the green sheet for a solid electrolyte is not particularly limited, and a known method such as a doctor blade method, a die coater, a comma coater, or a gravure coater can be adopted. Next, the active material layer, the current collector layer, and the active material layer are printed and laminated in this order on the green sheet for solid electrolyte by screen printing to form an electrode layer. Further, in order to fill the step between the solid electrolyte green sheet and the electrode layer, a margin layer is formed by screen printing in a region other than the electrode layer to prepare an electrode layer unit.

Then, the electrode layer units can be alternately offset so that one ends do not coincide with each other and laminated, and if necessary, outer layers (cover layers) can be provided on both main surfaces of the laminated body. By laminating the outer layer, a laminated substrate including a plurality of elements of the all-solid-state battery is produced. The outer layer 5 can be made of the same material as the solid electrolyte, and a green sheet for the solid electrolyte can be used.

The manufacturing method is for manufacturing a parallel type all-solid-state battery, but the manufacturing method for a series-type all-solid-state battery is such that one end and one end of each electrode layer coincide with each other, that is, no offset is performed. It may be laminated with.

Further, the produced laminated substrates can be collectively pressed by a die press, a hot water isotropic pressure press (WIP), a cold water isotropic pressure press (CIP), a hydrostatic pressure press, or the like to improve the adhesion. Pressurization is preferably performed while heating, and can be performed, for example, at 40 to 95 ° C.

The produced laminated substrate can be cut into a laminate of unfired all-solid-state batteries using a dicing device.

An all-solid-state battery is manufactured by removing and firing the laminate of the all-solid-state battery. De-bye and firing can be performed at a temperature of 600 ° C. to 1000 ° C. in a nitrogen atmosphere. The holding time for debuying and firing is, for example, 0.1 to 6 hours.

(R1-0.20d) ≤ R2 ≤ (R1-0.15d) ... (1)
0.0 <d ≦ 3.0… (2)
Conditions for satisfying the above equations (1) and (2) include, for example, Li _X Ti _1.9 V _0.1 (PO ₄ ) ₃ (1 ≦ x ≦ 3), Li on a solid electrolyte green sheet. _X Ti _1.7 V _0.3 (PO ₄ ) ₃ , Li _X Ti _1.5 V _0.5 (PO ₄ ) ₃ , Li _X Ti _1.3 V _0.7 (PO ₄ ) ₃ , Li _X Ti _1.1 V _0.9 (PO ₄ ) ₃ , Li _X Ti _0.9 V _1.1 (PO ₄ ) ₃ , Li _X Ti _0.7 V _1.3 (PO ₄ ) ₃ , Li _X Ti _0. Each active material having a composition of ₅ V _1.5 (PO ₄ ) ₃ , Li _X Ti _0.3 V _1.7 (PO ₄ ) ₃ , Li _X Ti _0.1 V _1.9 (PO ₄ ) ₃ It can be controlled by printing the paste containing the above thinly in order, but the method is not limited to this method.

In addition, two targets, Li _X Ti ₂ (PO ₄ ) ₃ and Li _X V ₂ (PO ₄ ) ₃ (1 ≤ X ≤ 3.5), were prepared and pulsed laser deposition was performed on the solid electrolyte green sheet. The ratio of Ti and V is controlled by adjusting the distance between the green sheet and the target of each target when film formation and deposition are performed using vapor phase methods such as the position method, vacuum deposition method, and sputtering method. It is also possible to do.

In addition, the formulas (1) and (2) can also be satisfied by appropriately adjusting the firing conditions (firing temperature and heating rate) in order to satisfy the formulas (1) and (2).

Further, an external electrode can be provided in order to efficiently draw current from the laminated body of the all-solid-state battery. The external electrodes are connected to one end of the electrode layer extending on both side surfaces of the laminate. Therefore, a pair of external electrodes 7 are formed so as to sandwich one side surface of the laminated body. Examples of the method for forming the external electrode include a sputtering method, a screen printing method, and a dip coating method. In the screen printing method and the dip coating method, a paste for an external electrode containing a metal powder, a resin, and a solvent is prepared and formed as an external electrode. Next, a baking step for removing the solvent and a plating process for forming a terminal electrode on the surface of the external electrode 7 are performed. On the other hand, in the sputtering method, since the external electrode and the terminal electrode can be directly formed, the baking step and the plating process are not required.

The laminated body of the all-solid-state battery 1 may be sealed in, for example, a coin cell in order to enhance moisture resistance and impact resistance. The sealing method is not particularly limited, and for example, the laminated body after firing may be sealed with a resin. Further, an insulating paste having an insulating property such as Al ₂ O ₃ may be applied or dip-coated around the laminate, and the insulating paste may be sealed by heat treatment.

Although the embodiment according to the present invention has been described in detail above, the embodiment is not limited to the above embodiment and can be variously modified.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples based on the above-described embodiment, but the present invention is not limited to these Examples. In addition, unless otherwise specified, the "parts" indication of the amount of the material charged in the preparation of the paste means "parts by mass".

(Example 1)
(Preparation of active material)
As active materials, Li _1.2 Ti _1.8 V _0.2 (PO ₄ ) ₃ , Li _1.4 Ti _1.6 V _0.4 (PO ₄ ) ₃ , Li _1.6 prepared by the following method. Ti _1.4 V _0.6 (PO ₄ ) ₃ , Li _1.8 Ti _1.2 V _0.8 (PO ₄ ) ₃ , Li ₂ TiV (PO ₄ ) ₃ , Li _2.2 Ti _0.8 V _1.2 (PO ₄ ) ₃ , Li _2.4 Ti _0.6 V _1.4 (PO ₄ ) ₃ , L _2.6 Ti _0.4 V _1.6 (PO ₄ ) ₃ , Li ₃ V ₂ (PO ₄ ) PO ₄ ) ₃ , was used. As a method for producing the powder, Li ₂ CO ₃ , V ₂ O ₅ , TIO ₂ and NH ₄ H ₂ PO ₄ are used as starting materials, wet-mixed with a ball mill for 16 hours, dehydrated and dried, and then the obtained powder is obtained. It was calcined in a nitrogen-hydrogen mixed gas at 850 ° C. for 2 hours. The calcined product was wet-pulverized with a ball mill and then dehydrated and dried to obtain each active material powder. The composition of the prepared powder was confirmed using an X-ray diffractometer. The ratio of Ti and V was prepared by adjusting the values of V ₂ O ₅ and TiO ₂ with the respective active material powders.

(Preparation of paste for active material layer)
The pastes for each active material layer are Li _1.2 Ti _1.8 V _0.2 (PO ₄ ) ₃ , Li _1.4 Ti _1.6 V _0.4 (PO ₄ ) ₃ , and Li _1.6 Ti. _1.4 V _0.6 (PO ₄ ) ₃ , Li _1.8 Ti _1.2 V _0.8 (PO ₄ ) ₃ , Li ₂ TiV (PO ₄ ) ₃ , Li _2.2 Ti _0.8 V _{1 .2} (PO ₄ ) ₃ , Li _2.4 Ti _0.6 V _1.4 (PO ₄ ) ₃ , Li _2.6 Ti _0.4 V _1.6 (PO ₄ ) ₃ , Li ₃ V ₂ (PO ₄ ) ₄ ) To 100 parts of each of the powders of ₃ and ₃ , 15 parts of ethyl cellulose as a binder and 65 parts of dihydroturpineol as a solvent were added, mixed and dispersed to prepare a paste for an active material layer of each component.

(Preparation of paste for solid electrolyte layer)
As the solid electrolyte, Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ prepared by the following method was used. The production method is as follows: Li ₂ CO ₃ , Al ₂ O ₃ , TIO ₂ and NH ₄ H ₂ PO ₄ are used as starting materials, wet-mixed in a ball mill for 16 hours, dehydrated and dried, and then the obtained powder is obtained. Was calcined in the air at 800 ° C. for 2 hours. After calcination, wet pulverization was performed in a ball mill for 16 hours, and then dehydration drying was performed to obtain a solid electrolyte powder. It was confirmed by using an X-ray diffractometer (XRD) that the composition of the prepared powder was Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ .

Next, 100 parts of ethanol and 200 parts of toluene were added as solvents to this powder and wet-mixed with a ball mill. Then, 16 parts of a polyvinyl butyral binder and 4.8 parts of benzylbutyl phthalate were further added and mixed to prepare a paste for a solid electrolyte layer.

(Preparation of sheet for solid electrolyte layer)
A sheet of the solid electrolyte layer paste was formed by a doctor blade method using a PET film as a base material to obtain a solid electrolyte layer sheet having a thickness of 15 μm.

(Preparation of paste for current collector layer)
As a current collector, Cu and Li ₃ V ₂ (PO ₄ ) ₃ are mixed so as to have a volume ratio of 80/20, and then 10 parts of ethyl cellulose as a binder and 50 parts of dihydroterpineol as a solvent are added and mixed. It was dispersed to prepare a paste for the current collector layer.

(Preparation of paste for margin layer)
The paste for the margin layer is prepared by adding 100 parts of ethanol and 100 parts of toluene as a solvent to the powder of Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ and wet-mixing them with a ball mill, and then using a polyvinyl butyl system. 16 parts of the binder and 4.8 parts of benzyl butyl phthalate were further added and mixed to prepare a paste for the margin layer.

(Preparation of external electrode paste)
A thermosetting external electrode paste was prepared by mixing and dispersing silver powder, an epoxy resin, and a solvent.

Using these pastes, an all-solid-state battery was prepared as follows.

(Manufacturing of electrode layer unit)
_Three layers of Li _1.2 Ti _1.8 V _0.2 (PO ₄ ) having a thickness of 0.55 μm were printed on the solid electrolyte layer sheet to form the solid electrolyte layer, and dried at 80 ° C. for 10 minutes. On top of that, in the same procedure, each 0.55 μm thick Li _1.4 Ti _1.6 V _0.4 (PO ₄ ) ₃ layers, Li _1.6 Ti _1.4 V _0.6 (PO ₄ ) ₃ layers, Li _1.8 Ti _1.2 V _0.8 (PO ₄ ) ₃ layers, Li ₂ TiV (PO ₄ ) ₃ layers, Li _2.2 Ti _0.8 V _1.2 (PO ₄ ) ₃ layers , Li _2.4 Ti _0.6 V _1.4 (PO ₄ ) ₃ layers, Li _2.6 Ti _0.4 V _1.6 (PO ₄ ) ₃ layers, Li ₃ V ₂ (PO ₄ ) ₃ layers Formed. A current collector layer having a thickness of 5 μm was formed on the current collector layer by screen printing, and dried at 80 ° C. for 10 minutes. Further, ₃ layers of Li ₃ V ₂ (PO ₄ ) having a thickness of 0.55 μm were printed and formed on the same layer, and dried at 80 ° C. for 10 minutes. On top of that, in the same procedure, each 0.55 μm thick Li _2.8 Ti _0.2 V _1.8 (PO ₄ ) ₃ layers, Li _2.6 Ti _0.4 V _1.6 (PO ₄ ) ₃ layers, Li _2.4 Ti _0.6 V _1.4 (PO ₄ ) ₃ layers, Li _2.2 Ti _0.8 V _1.2 (PO ₄ ) ₃ layers, Li ₂ TiV (PO ₄ ) ₃ layers , Li _1.8 Ti _1.2 V _0.8 (PO ₄ ) ₃ layers, Li _1.6 Ti _1.4 V _0.6 (PO ₄ ) ₃ layers, Li _1.4 Ti _1.6 V _0. By forming ₃ layers of ₄ (PO ₄ ) and ₃ layers of Li _1.2 Ti _1.8 V _0.2 (PO ₄ ), an electrode layer was prepared on a sheet for a solid electrolyte layer. Next, a margin layer 80 having a height substantially flush with the electrode layer was formed on the outer periphery of one end of the electrode layer by screen printing, and dried at 80 ° C. for 10 minutes. Then, the PET film was peeled off to obtain a sheet of the electrode layer unit.

(Preparation of laminate)
A plurality of electrode layer units were alternately laminated while being offset so that one ends of the two electrode layer units did not match, to prepare a laminated substrate. Further, a plurality of solid electrolyte sheets were laminated as outer layers on both main surfaces of the laminated substrate, and an outer layer of 500 μm was provided. This was thermocompression bonded by a die press and then cut to prepare an unfired all-solid-state battery laminate. Next, the laminate was debuy-fired to obtain an all-solid-state battery laminate. The calcination was carried out in nitrogen at a calcination rate of 40 ° C./min to a calcination temperature of 830 ° C., held at that temperature for 21 minutes, and taken out after natural cooling.

(External electrode forming process)
An external electrode paste was applied to the end faces of the laminated body of the all-solid-state battery, and thermosetting was performed at 150 ° C. for 30 minutes to form a pair of external electrodes.

For the obtained all-solid-state battery, the interface between the active material and the solid electrolyte was analyzed by SEM-EDS and TEM-EDS, and the atomic weight ratio of Ti to V contained in the active material from the interface toward the current collector layer Ti / ( When Ti + V) was calculated, it was as shown in Table 1.

(Example 2)
The all-solid-state battery according to the second embodiment is formed by printing _three layers of Li _1.2 Ti _1.8 V _0.2 (PO ₄ ) having a thickness of 0.65 μm on the above-mentioned sheet for the solid electrolyte layer. , 80 ° C. for 10 minutes. On top of that, in the same procedure, each 0.65 μm thick Li _1.4 Ti _1.6 V _0.4 (PO ₄ ) ₃ layers, Li _1.6 Ti _1.4 V _0.6 (PO ₄ ) ₃ layers, 0.75 μm thick Li _1.8 Ti _1.2 V _0.8 (PO ₄ ) ₃ layers, 1.15 μm thick Li ₂ TiV (PO ₄ ) ₃ layers, Li _2.2 Ti _Three layers of _0.8 V _1.2 (PO ₄ ) were formed. A current collector layer having a thickness of 5 μm was formed on the current collector layer by screen printing, and dried at 80 ° C. for 10 minutes. Further, _three layers of Li _2.2 Ti _0.8 V _1.2 (PO ₄ ) having a thickness of 1.15 μm were printed and formed on the same layer, and dried at 80 ° C. for 10 minutes. The same procedure _{thereon, Li 2 TiV (PO 4)} 3 -layer thickness _{1.15μm, Li 1.8 Ti 1.2 V 0.8} (PO 4) having a thickness of 0.75 .mu.m ₃ layers, each Li _1.6 Ti _1.4 V _0.6 (PO ₄ ) ₃ layers with a thickness of 0.65 μm, Li _1.4 Ti _1.6 V _0.4 (PO ₄ ) ₃ layers, Li _1.2 Ti ₁ By forming _three layers of _.8 V _0.2 (PO ₄ ), an electrode layer was prepared on a sheet for a solid electrolyte layer. Other than that, an all-solid-state battery was produced in the same manner as in Example 1. For the obtained all-solid-state battery, the interface between the active material and the solid electrolyte was analyzed by SEM-EDS and TEM-EDS, and the atomic weight ratio of Ti to V contained in the active material from the interface toward the current collector layer Ti / ( When Ti + V) was calculated, it was as shown in Table 1.

(Example 3)
The all-solid-state battery according to the third embodiment is formed by printing _three layers of Li _1.2 Ti _1.8 V _0.2 (PO ₄ ) having a thickness of 0.65 μm on the above-mentioned sheet for the solid electrolyte layer. , 80 ° C. for 10 minutes. On top of that, follow the same procedure, with ₃ layers of Li _1.4 Ti _1.6 V _0.4 (PO ₄ ) with a thickness of 0.65 μm, and Li _1.6 Ti _1.4 V _{0 with a} thickness of 0.75 μm each. _.6 (PO ₄ ) ₃ layers, Li _1.8 Ti _1.2 V _0.8 (PO ₄ ) ₃ layers, each 1.10 μm thickness Li ₂ TiV (PO ₄ ) ₃ layers, Li _2.2 Ti _Three layers of _0.8 V _1.2 (PO ₄ ) were formed. A current collector layer having a thickness of 5 μm was formed on the current collector layer by screen printing, and dried at 80 ° C. for 10 minutes. Further, _three layers of Li _2.2 Ti _0.8 V _1.2 (PO ₄ ) having a thickness of 1.10 μm were printed and formed on the same layer, and dried at 80 ° C. for 10 minutes. The same procedure _{thereon, Li 2 TiV (PO 4)} 3 -layer thickness _{1.10μm, Li 1.8 Ti 1.2 V 0.8} (PO 4) of the thickness of 0.75 .mu.m ₃ layers, Li _1.6 Ti _1.4 V _0.6 (PO ₄ ) ₃ layers, each 0.65 μm thick Li _1.4 Ti _1.6 V _0.4 (PO ₄ ) ₃ layers, Li _1.2 Ti By forming _three layers of _1.8 V _0.2 (PO ₄ ), an electrode layer was prepared on a sheet for a solid electrolyte layer. Other than that, an all-solid-state battery was produced in the same manner as in Example 1. For the obtained all-solid-state battery, the interface between the active material and the solid electrolyte was analyzed by SEM-EDS and TEM-EDS, and the atomic weight ratio of Ti to V contained in the active material from the interface toward the current collector layer Ti / ( When Ti + V) was calculated, it was as shown in Table 1.

(Example 4)
In the all-solid-state battery according to Example 4, the sintering conditions of the laminate described in Example 3 were changed to create a more reducing atmosphere, the temperature rising rate was changed to 0.50 times, and the firing temperature was changed to 850 ° C. Made an all-solid-state battery in the same manner as in Example 1. For the obtained all-solid-state battery, the interface between the active material and the solid electrolyte was analyzed by SEM-EDS and TEM-EDS, and the atomic weight ratio of Ti to V contained in the active material from the interface toward the current collector layer Ti / ( When Ti + V) was calculated, it was as shown in Table 1.

(Comparative Example 1)
The all-solid-state battery according to Comparative Example 1 was formed by printing _three layers of Li _1.2 Ti _1.8 V _0.2 (PO ₄ ) having a thickness of 1.10 μm on the above-mentioned sheet for the solid electrolyte layer. , 80 ° C. for 10 minutes. On top of that, in the same procedure, each 0.55 μm thick Li _1.4 Ti _1.6 V _0.4 (PO ₄ ) ₃ layers, Li _1.6 Ti _1.4 V _0.6 (PO ₄ ) ₃ layers, each 0.65 μm thick Li _1.8 Ti _1.2 V _0.8 (PO ₄ ) ₃ layers, Li ₂ TiV (PO ₄ ) ₃ layers, Li _2.2 Ti _0.8 V _{1. 2} (PO ₄ ) ₃ layers and Li _2.4 Ti _0.6 V _1.4 (PO ₄ ) ₃ layers were formed. A current collector layer having a thickness of 5 μm was formed on the current collector layer by screen printing, and dried at 80 ° C. for 10 minutes. Further, _three layers of Li _2.4 Ti _0.6 V _1.4 (PO ₄ ) having a thickness of 0.65 μm were printed and formed on the same layer, and dried at 80 ° C. for 10 minutes. On top of that, in the same procedure, Li _2.2 Ti _0.8 V _1.2 (PO ₄ ) ₃ layers, Li ₂ TiV (PO ₄ ) ₃ layers, Li _1.8 Ti _{1 with} each thickness of 0.65 μm. _.2 V _0.8 (PO ₄ ) ₃ layers, Li _1.6 Ti _1.4 V _0.6 (PO ₄ ) ₃ layers each 0.55 μm thick, Li _1.4 Ti _1.6 V _{0. An} electrode layer was prepared on the solid electrolyte layer sheet by forming ₃ layers of ₄ (PO ₄ ) and ₃ layers of Li _1.2 Ti _1.8 V _0.2 (PO ₄ ) having a thickness of 1.10 μm. Other than that, an all-solid-state battery was produced in the same manner as in Example 1. For the obtained all-solid-state battery, the interface between the active material and the solid electrolyte was analyzed by SEM-EDS and TEM-EDS, and the atomic weight ratio of Ti to V contained in the active material from the interface toward the current collector layer Ti / ( When Ti + V) was calculated, it was as shown in Table 1.

(Comparative Example 2)
The all-solid-state battery according to Comparative Example 2 was the same as in Example 1 except that the sintering conditions of the laminate were changed, the heating rate was changed to 1.5 times, and the holding time was changed to 0.67 times. An all-solid-state battery was manufactured. For the obtained all-solid-state battery, the interface between the active material and the solid electrolyte was analyzed by SEM-EDS and TEM-EDS, and the atomic weight ratio of Ti to V contained in the active material from the interface toward the current collector layer Ti / ( When Ti + V) was calculated, it was as shown in Table 1.

(Battery evaluation)
The all-solid-state batteries produced in this example and comparative examples can be evaluated for the following battery characteristics.

[Charge / discharge test]
The charge / discharge cycle characteristics of the all-solid-state batteries produced in this example and the comparative example can be evaluated, for example, under the charge / discharge conditions shown below. For the notation of charge / discharge current, the C (sea) rate notation will be used hereafter. The C rate is expressed as nC (μA) (n is a numerical value) and means a current capable of charging / discharging the nominal capacitance (μAh) at 1 / n (h). For example, 1C means a charge / discharge current capable of charging the nominal capacity in 1h, and 2C means a charge / discharge current capable of charging the nominal capacity in 0.5h. For example, in the case of an all-solid-state battery having a nominal capacity of 100 μAh, the current of 0.1 C is 10 μA (calculation formula 100 μA × 0.1 = 10 μA). Similarly, the current of 0.2C is 20 μA, and the current of 1C is 100 μA.

The charge / discharge test conditions are: in an environment of 25 ° C., constant current charging (CC charging) is performed at a constant current of 0.2 C rate until the battery voltage reaches 1.6 V, and then at a constant current of 0.2 C rate. It was discharged until the battery voltage reached 0 V (CC discharge). The charging and discharging were set as one cycle, and this was repeated for 10 cycles. The discharge capacity in the first cycle was evaluated as the theoretical capacity retention rate. Then, constant current charging (CC charging) was performed until the battery voltage reached 1.6 V at a constant current of 1 C rate, and then discharged until the battery voltage reached 0 V at a constant current of 1 C rate (CC discharge). The discharge capacity retention rate after changing the C rate was evaluated as a rate characteristic. The initial discharge capacity and rate characteristics in this embodiment were calculated by the following formulas.
Theoretical capacity retention rate (%) = (Theoretical capacity of the all-solid-state battery calculated from the discharge capacity of the first cycle ÷ the amount of active material) x 100
Discharge capacity retention rate after changing C rate (%) = (Capacity during CC discharge at 1 C rate ÷ Capacity during CC discharge at 0.2 C rate) x 100

(result)
Table 1 shows the results of the theoretical capacity retention rate and the discharge capacity retention rate after changing the C rate of the all-solid-state batteries according to Examples 1 to 4 and Comparative Examples 1 and 2. In the all-solid-state batteries according to Examples 1 to 4, it was confirmed that the theoretical capacity retention rate and the rate characteristics were superior to those of the all-solid-state batteries according to the comparative examples.

Although the present invention has been described in detail above, the embodiments and examples are merely examples, and the inventions disclosed herein include various modifications and modifications of the above-mentioned specific examples.

1 ... All-solid-state battery 20 ... Laminated body 30 ... Positive electrode 31 ......... Positive electrode current collector layer 32 ......... Positive electrode active material layer 40 ... Negative electrode 41 ......... Negative electrode current collector layer 42 ... Material layer 50 ... Solid electrolyte layer 60 ... Positive electrode external electrode 70 ... Negative electrode external electrode 80 ... Margin layer 90 ... Interface DR1 ... Depth direction

Claims (1)

A plurality of electrode layers in which a current collector layer and an active material layer are laminated are laminated via a solid electrolyte layer, and a laminate.
Includes an interface between the solid electrolyte layer and the active material layer.
The active material layer contains Ti and V, and contains
When the direction from the interface to the current collector layer closest to the interface is defined as the depth direction in the same direction as the stacking direction,
An all-solid-state battery satisfying the formulas (1) and (2).
(R1-0.20d) ≤ R2 ≤ (R1-0.15d) ... (1)
0.0 <d ≤ 3.0 ... (2)
(D indicates the distance (μm) from the interface in the depth direction.
R1 represents the atomic weight ratio (Ti / (Ti + V)) of Ti and V in the active material layer at the interface.
R2 represents the atomic weight ratio (Ti / (Ti + V)) of Ti and V in the active material layer at the point d. )

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