WO2014171309A1

WO2014171309A1 - All-solid-state cell

Info

Publication number: WO2014171309A1
Application number: PCT/JP2014/059288
Authority: WO
Inventors: 大塚春男; 鬼頭賢信
Original assignee: 日本碍子株式会社
Priority date: 2013-04-17
Filing date: 2014-03-28
Publication date: 2014-10-23

Abstract

This all-solid-state cell comprises a solid electrolyte layer (14), a positive electrode-side collector (16), a positive electrode layer (18), a negative electrode-side collector (20), and a negative electrode layer (22). The positive electrode layer (18) is connected with the positive electrode-side collector (16). The negative electrode layer (22) is connected with the negative electrode-side collector (20). The positive electrode layer (18) and the negative electrode layer (22) are layered in an alternating fashion. The solid electrolyte layer (14) is interposed between the positive electrode layer (18) and the negative electrode layer (22), between the positive electrode layer (18) and the negative electrode-side collector (20), and between the negative electrode layer (22) and the positive electrode-side collector (16).

Description

All solid battery

The present invention relates to an all-solid battery using a combination of an electrode active material and a solid electrolyte.

In recent years, with the development of portable devices such as personal computers and mobile phones, the demand for batteries as the power source has greatly increased. In a battery used for such an application, a liquid electrolyte (electrolytic solution) such as an organic solvent using a flammable organic solvent as a diluent solvent has been conventionally used as a medium for moving ions. A battery using such an electrolytic solution may cause problems such as leakage of the electrolytic solution, ignition, and explosion.

In order to solve these problems, in order to ensure essential safety, the development of an all-solid-state battery in which a solid electrolyte is used instead of a liquid electrolyte and all other elements are made of solid is being promoted. ing. Such an all-solid battery has a solid electrolyte, so there is little fear of ignition, no leakage, and problems such as deterioration of battery performance due to corrosion hardly occur.

By the way, the electrode formed by coating on the current collector contains many organic binders that do not directly contribute to the battery characteristics, and a lot of electron conduction assistants that assist the electron conduction between the particles. The active material filling rate in the electrode was lowered, resulting in a reduction in battery capacity and a decrease in energy density. In order to improve the energy density, the filling rate of the active material forming the electrode must be increased. Therefore, the battery described in Japanese Patent Application Laid-Open No. 2002-42785 is a lithium battery in which an electrolyte is sandwiched between a pair of electrodes, and the electrode thickness is formed of a sintered body exceeding 20 μm and not more than 200 μm, and The filling rate of the active material in the electrode is 50 to 80%.

In a conventional all-solid battery, a solid electrolyte is sandwiched between a positive electrode and a negative electrode, a positive current collector is installed on the end face of the positive electrode, and a negative current collector is installed on the end face of the negative electrode. It is composed. Therefore, in order to increase energy, it is conceivable to stack a plurality of cells. In this case, it is easy to increase the energy by stacking a plurality of cells connected in series, but it is difficult to increase the energy by stacking a plurality of cells connected in parallel. is there. That is, the conventional all-solid-state battery has a problem that the degree of freedom is small when designing a laminated structure, and it cannot cope with various specifications.

The present invention has been made in view of such problems, and when stacking a plurality of cells to increase energy, series connection, parallel connection, and combinations thereof can be easily realized, An object of the present invention is to provide an all-solid-state battery that can improve the degree of freedom of design and can cope with various specifications.

[1] An all solid state battery according to the first aspect of the present invention includes a solid electrolyte layer, a positive electrode side current collector, a positive electrode layer connected to the positive electrode side current collector, a negative electrode side current collector, and a negative electrode side current collector. A positive electrode layer connected to an electric body, the positive electrode layer and the negative electrode layer are alternately stacked, and between the positive electrode layer and the negative electrode layer, between the positive electrode layer and the negative electrode side current collector The solid electrolyte layer is interposed between and between the negative electrode layer and the positive electrode side current collector.

The structure of a normal all-solid battery includes a laminate in which a negative electrode side current collector, a negative electrode layer, a solid electrolyte layer, a positive electrode layer, and a positive electrode side current collector are sequentially laminated. In this case, since the energy of the all solid state battery is small, it is inevitably possible to increase the energy by stacking a plurality of all solid state batteries. However, in the structure of the laminated body described above, it is easy to increase the energy in series, but it is difficult to improve the energy in parallel.

On the other hand, if it is the structure of the all-solid-state battery according to the first aspect of the present invention, a plurality of all-solid-state batteries can be combined to freely connect a plurality of all-solid-state batteries in parallel, a series connection, and a combination thereof. In addition, it can be easily configured, and the number of series and the number of parallel can be arbitrarily selected depending on the combination of all solid state batteries, and the degree of freedom in design can be improved.

[2] In the first aspect of the present invention, the positive electrode side current collector and the negative electrode side current collector may face each other.

[3] In the first aspect of the present invention, the negative electrode layer includes a first negative electrode layer and a second negative electrode layer, and the first negative electrode layer, the positive electrode layer, and the second negative electrode layer are alternately arranged. The solid electrolyte layer is laminated, the first solid electrolyte layer interposed between the positive electrode side current collector and the first negative electrode layer, the positive electrode side current collector and the negative electrode side current collector And a third solid interposed between the second negative electrolyte layer interposed between the first negative electrode layer and the positive electrode layer, and between the positive electrode layer and the negative electrode side current collector. A fourth solid electrolyte layer interposed between the electrolyte layer, the positive electrode current collector and the negative electrode current collector, and interposed between the second negative electrode layer and the positive electrode layer; You may have the 5th solid electrolyte layer interposed between the positive electrode side electrical power collector and the said 2nd negative electrode layer.

[4] In the first aspect of the present invention, the lithium ion conductive material constituting the solid electrolyte layer is composed of a garnet-based, nitride-based, perovskite-based, phosphate-based, sulfide-based, or polymer-based material. It may be.

[5] In the first aspect of the present invention, the positive electrode layer may be composed of only a positive electrode active material in which a specific crystal plane is oriented in a lithium ion conduction direction.

[6] In this case, the positive electrode active material may have a layered rock salt structure or a spinel structure.

[7] Furthermore, the positive electrode active material includes:
General formula: Li _p (Ni _x Co _y Al _z ) O ₂
(In the above general formula, 0.9 ≦ p ≦ 1.3, 0.6 <x <0.9, 0.1 <y ≦ 0.3, 0 ≦ z ≦ 0.2, x + y + z = 1)
The specific crystal plane may be a (003) plane.

[8] In the first aspect of the present invention, the positive electrode layer may be configured by mixing a positive electrode active material, a solid electrolyte material, and a conductive additive and compacting the mixture.

[9] In this case, the positive electrode active material is
General formula: Li _p (Ni _x Co _y Al _z ) O ₂
(In the above general formula, 0.9 ≦ p ≦ 1.3, 0.6 <x <0.9, 0.1 <y ≦ 0.3, 0 ≦ z ≦ 0.2, x + y + z = 1)
The solid electrolyte material has a garnet-based crystal structure containing Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ), and the conductive additive is acetylene black. Also good.

[10] In the first aspect of the present invention, the negative electrode layer may be composed of only a negative electrode active material.

[11] In this case, the negative electrode active material may be an oxide-based material.

[12] Further, the negative electrode active material may be Li ₄ Ti ₅ O ₁₂ or TiO ₂ .

[13] In this case, the negative electrode active material may be a carbon-based material.

[14] Furthermore, the negative electrode active material may be graphite, soft carbon, hard carbon, carbon nanotube, or graphene.

[15] In the first aspect of the present invention, the negative electrode layer may be configured by mixing a negative electrode active material and a solid electrolyte material and compacting the mixture.

[16] In this case, the negative electrode active material may be graphite, and the solid electrolyte material may have a garnet-based crystal structure including Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ).

[17] An all solid state battery according to a second aspect of the present invention is an all solid state battery configured by laminating a plurality of single cells, the single cell comprising a solid electrolyte layer, a positive electrode side current collector, A positive electrode layer connected to the positive electrode side current collector, a negative electrode side current collector, and a negative electrode layer connected to the negative electrode side current collector, wherein the positive electrode layer and the negative electrode layer are alternately stacked; The solid electrolyte layer is interposed between the positive electrode layer and the negative electrode layer, between the positive electrode layer and the negative electrode side current collector, and between the negative electrode layer and the positive electrode side current collector. Features.

As a result, when a plurality of single cells are combined to increase energy, series connection, parallel connection, and combinations thereof can be easily realized, and design flexibility can be improved. It can cope with various specifications. In other words, depending on how the single cells are combined, the number of series and the number of parallel can be arbitrarily selected, and the degree of freedom in design can be improved.

[18] In the second aspect of the present invention, an insulating layer may be interposed between at least one adjacent single cell among the plurality of single cells arranged in the stacking direction.

[19] In the second aspect of the present invention, an insulating layer may be interposed between at least one adjacent unit cell among the plurality of unit cells arranged in the lateral direction.

[20] In the second aspect of the present invention, a current collector plate connected to the negative electrode side current collector or the positive electrode side current collector may be provided on both end faces of each single cell.

[21] In the second aspect of the present invention, a current collector may be interposed between the single cells arranged in the lateral direction.

As described above, according to the all solid state battery of the present invention, when stacking a plurality of single cells to increase energy, series connection, parallel connection, and a combination thereof can be easily realized. Thus, the degree of freedom in design can be improved and various specifications can be accommodated.

FIG. 1A is a cross-sectional view showing the structure of a single cell of an all solid state battery according to the present embodiment, and FIG. 1B is an exploded perspective view showing the structure of a single cell. FIG. 2A is a cross-sectional view showing the structure of a single cell of a general all solid state battery, and FIG. 2B is an exploded perspective view showing the structure of a single cell. FIG. 3A is a cross-sectional view showing the structure of an all solid state battery (first all solid state battery) according to a first specific example, and FIG. 3B is an equivalent circuit diagram showing the first all solid state battery. FIG. 4A is a cross-sectional view showing the structure of an all solid state battery (second all solid state battery) according to a second specific example, and FIG. 4B is an equivalent circuit diagram showing the second all solid state battery. FIG. 5A is a cross-sectional view showing the structure of an all solid state battery (third all solid state battery) according to a third specific example, and FIG. 5B is an equivalent circuit diagram showing the third all solid state battery. FIG. 6A is a cross-sectional view showing the structure of an all solid state battery (fourth all solid state battery) according to a fourth specific example, and FIG. 6B is an equivalent circuit diagram showing the fourth all solid state battery. FIG. 7A is a sectional view showing the structure of an all solid state battery (fifth all solid state battery) according to a fifth specific example, and FIG. 7B is an equivalent circuit diagram showing the fifth all solid state battery. FIG. 8A is a sectional view showing the structure of an all solid state battery (sixth all solid state battery) according to a sixth specific example, and FIG. 8B is an equivalent circuit diagram showing the sixth all solid state battery. FIG. 9A is a sectional view showing the structure of an all solid state battery (seventh all solid state battery) according to a seventh example, and FIG. 9B is an equivalent circuit diagram showing the seventh all solid state battery.

Hereinafter, embodiments of the all-solid-state battery according to the present invention will be described with reference to FIGS. 1A to 9B.

As shown in FIGS. 1A and 1B, the structure of the single cell 12 of the all solid state battery 10 according to the present embodiment is connected to the solid electrolyte layer 14, the positive electrode side current collector 16, and the positive electrode side current collector 16. The positive electrode layer 18, the negative electrode side current collector 20, and the negative electrode layer 22 connected to the negative electrode side current collector 20 are included. The positive electrode side current collector 16 and the negative electrode side current collector 20 face each other.

Further, the single cell 12 includes positive electrode layers 18 and negative electrode layers 22 that are alternately stacked, between the positive electrode layer 18 and the negative electrode layer 22, between the positive electrode layer 18 and the negative electrode side current collector 20, and the negative electrode layer 22. Solid electrolyte layers 14 are interposed between the positive electrode side current collectors 16.

Specifically, the negative electrode layer 22 includes a first negative electrode layer 22a and a second negative electrode layer 22b, and the first negative electrode layer 22a, the positive electrode layer 18, and the second negative electrode layer 22b are alternately stacked.

The solid electrolyte layer 14 is formed between the first solid electrolyte layer 14a interposed between the positive electrode side current collector 16 and the first negative electrode layer 22a, and between the positive electrode side current collector 16 and the negative electrode side current collector 20. A third solid electrolyte interposed between the second solid electrolyte layer 14 b interposed between the first negative electrode layer 22 a and the positive electrode layer 18, and the positive electrode layer 18 and the negative electrode side current collector 20. A fourth solid electrolyte layer 14d interposed between the second negative electrode layer 22b and the positive electrode layer 18 between the layer 14c and the positive electrode side current collector 16 and the negative electrode side current collector 20, It has the 5th solid electrolyte layer 14e interposed between the positive electrode side collector 16 and the 2nd negative electrode layer 22b. In addition, each component material and manufacturing method of the positive electrode layer 18, the negative electrode layer 22, and the solid electrolyte layer 14 are mentioned later.

For example, as shown in FIGS. 2A and 2B, the structure of a single cell 102 of a normal all-solid-state battery 100 includes a negative electrode side current collector 104, a negative electrode layer 106, a solid electrolyte layer 108, a positive electrode layer 110, and a positive electrode side current collector. A laminate 114 in which 112 are laminated in order is mentioned. In this case, since the energy of the single cell 102 is small, it is inevitably possible to increase the energy by stacking a plurality of stacked bodies 114. However, in the structure of the stacked body 114, it is easy to increase the energy in series, but it is difficult to improve the energy in parallel.

On the other hand, if it is the structure of the single cell 12 of the all-solid-state battery 10 which concerns on this Embodiment mentioned above, the parallel connection of the several single cell 12 is carried out by combining the several single cell 12 so that it may mention later. In addition, series connection and combinations thereof can be freely and easily configured, and the number of series and parallel can be arbitrarily selected depending on the combination of single cells 12 and the degree of design freedom is improved. Can be made.

Here, a specific example of a structure (all solid state battery) composed of a combination of a plurality of single cells 12 will be described with reference to FIGS. 3A to 9B.

The all solid state battery according to the first specific example (hereinafter referred to as the first all solid state battery 10A) is configured by stacking three single cells 12 as shown in FIG. 3A. An insulating layer 24 is interposed between the single cells 12 adjacent to each other in the stacking direction. Each of the positive electrode side current collector 16 and the negative electrode side current collector 20 is constituted by one current collector, and is common to the three single cells 12. According to the first all-solid-state battery 10A, as shown in FIG. 3B, a configuration in which three single cells 12 are connected in parallel can be realized.

As shown in FIG. 4A, the all-solid battery according to the second specific example (hereinafter referred to as the second all-solid battery 10B) has two first all-solid batteries 10A arranged in the horizontal direction. A relay current collector 26 is interposed between the solid state batteries 10A. The relay current collector 26 is common to the six single cells 12. According to the second all-solid-state battery 10B, as shown in FIG. 4B, it is possible to realize a configuration in which two parallel circuits 28 in which three single cells 12 are connected in parallel are connected in series.

As shown in FIG. 5A, the all-solid battery according to the third specific example (hereinafter referred to as the third all-solid battery 10C) has substantially the same configuration as the first all-solid battery 10A, but the insulating layer 24 is Instead, it differs in that each single cell 12 has current collector plates 30 connected to the negative electrode side current collector 20 or the positive electrode side current collector 16 on both end surfaces (upper surface and lower surface) of each unit cell 12. In the example of FIG. 5A, the example which connected each current collecting plate 30 to the negative electrode side collector 20 is shown. According to the third all solid state battery 10C, as shown in FIG. 5B, a configuration in which three single cells 12 are connected in parallel can be realized.

As shown in FIG. 6A, an all-solid battery according to a fourth specific example (hereinafter referred to as a fourth all-solid battery 10D) has two third all-solid batteries 10C arranged in the horizontal direction. A relay current collector 26 is interposed between the solid batteries 10C. The relay current collector 26 is common to the six single cells 12. According to the fourth all solid state battery 10D, as shown in FIG. 6B, it is possible to realize a configuration in which two parallel circuits 28 in which three single cells 12 are connected in parallel are connected in series.

As shown in FIG. 7A, an all-solid battery according to a fifth specific example (hereinafter referred to as a fifth all-solid battery 10E) has two unit cells 12 arranged in the horizontal direction and an insulating layer 24 between the unit cells 12. Further, the positive electrode layer 18 of one unit cell 12 and the negative electrode layer 22 of the other unit cell 12 are connected by a relay current collector 26. According to the fifth all solid state battery 10E, as shown in FIG. 7B, a configuration in which two single cells 12 are connected in series can be realized.

As shown in FIG. 8A, an all-solid battery according to the sixth specific example (hereinafter referred to as a sixth all-solid battery 10F) includes three unit cells 12 (first unit cell 12A and second unit cell 12B from the top). And the third single cell 12C) is laminated. In the first single cell 12A and the third single cell 12C, the negative electrode side current collector 20 is located on the right side in FIG. 8A, and in the second single cell 12B, the negative electrode side current collector 20 is located on the left side in FIG. 8A. is doing. Further, current collecting plates 30 connected to the negative electrode current collector 20 are provided on both end surfaces (upper surface and lower surface) of the first single cell 12A to the third single cell 12C. Further, the first insulating layer 24a is interposed between the first single cell 12A and the second single cell 12B, and the positive current collector 16 of the first single cell 12A and the negative current collector 20 of the second single cell 12B. Are electrically insulated, and the second insulating layer 24b is interposed between the second unit cell 12B and the third unit cell 12C, so that the positive electrode side current collector 16 of the second unit cell 12B and the third unit cell 12C The negative electrode side current collector 20 is electrically insulated. Further, the negative electrode side current collector 20 of the first single cell 12A and the positive electrode side current collector 16 of the second single cell 12B are made common to form the first common electrode 32A, and the negative electrode side current collector of the second single cell 12B. The electric current body 20 and the positive electrode side current collector 16 of the third single cell 12C are made common to form a second common electrode 32B. According to the sixth all solid state battery 10F, as shown in FIG. 8B, a configuration in which the first single cell 12A, the second single cell 12B, and the third single cell 12C are connected in series can be realized.

As shown in FIG. 9A, an all-solid battery according to the seventh specific example (hereinafter referred to as a seventh all-solid battery 10G) includes four single cells 12 (first single cell 12A and second single cell 12B from the top). The third unit cell 12C and the fourth unit cell 12D) are stacked. The first single cell 12A and the second single cell 12B have the negative electrode current collector 20 positioned on the right side in FIG. 9A, and the third single cell 12C and the fourth single cell 12D have the negative electrode side on the left side in FIG. 9A. The current collector 20 is located. In addition, current collector plates 30 connected to the negative electrode current collector 20 are provided on both end surfaces (upper surface and lower surface) of the first unit cell 12A to the fourth unit cell 12D. Further, an insulating layer 24 is interposed between the second unit cell 12B and the third unit cell 12C, and the positive electrode side current collector 16 common to the first unit cell 12A and the second unit cell 12B, and the third unit cell 12C. And the common negative electrode side collector 20 of 4th single cell 12D is electrically insulated. Further, the negative electrode side current collectors 20 of the first single cell 12A and the second single cell 12B and the positive electrode side current collectors 16 of the third single cell 12C and the fourth single cell 12D are made common, respectively. 32. According to the seventh all solid state battery 10G, as shown in FIG. 9B, the first parallel circuit 28A, the third single cell 12C, and the fourth single cell in which the first single cell 12A and the second single cell 12B are connected in parallel. The structure which connected in series with the 2nd parallel circuit 28B which connected 12D in parallel is realizable.

The above-described example is merely an example, and various other combinations of the single cells 12 are conceivable, and it is a matter of course that various parallel / series connections of the plurality of single cells 12 can be configured.

As described above, in the all solid state battery 10 according to the present embodiment, when a plurality of single cells 12 are combined to increase energy, series connection, parallel connection, and combinations thereof can be easily realized. Thus, the degree of freedom in design can be improved and various specifications can be accommodated. In other words, depending on how the single cells 12 are combined, the number of series and the number of parallel can be arbitrarily selected, and the degree of freedom in design can be improved.

Here, each constituent material of the positive electrode layer 18, the negative electrode layer 22, and the solid electrolyte layer 14 will be described.

First, the positive electrode layer 18 is composed of a plurality of lithium transition metal oxide particles (positive electrode active material), and the lithium ion conduction direction of each particle is oriented in a fixed direction. The certain direction is a direction perpendicular to the interface between the positive electrode layer 18 and the solid electrolyte layer 14. In this embodiment, the positive electrode layer 18 has a specific crystal plane of each particle from the positive electrode layer 18 toward the negative electrode layer 22. It is composed of layers oriented in the direction. That is, the positive electrode layer 18 is configured by sintering only particles (positive electrode active material) in which a specific crystal plane is oriented in the lithium ion conduction direction. The positive electrode active material has a layered rock salt structure or a spinel structure.

Specifically, when a positive electrode active material having a layered rock salt structure is used, particles having a composition represented by the following general formula and having a thickness of about 2 to 100 μm are preferable.
General formula: Li _p (Ni _x Co _y Al _z ) O ₂
(In the above general formula, 0.9 ≦ p ≦ 1.3, 0.6 <x <0.9, 0.1 <y ≦ 0.3, 0 ≦ z ≦ 0.2, x + y + z = 1)

In particular, it is preferable that the specific crystal plane described above is a (003) plane, and the (003) plane is oriented in a direction from the positive electrode layer 18 toward the negative electrode layer 22. Thereby, it does not become resistance at the time of insertion / removal of the lithium ion to the positive electrode layer 18 but can release a lot of lithium ions at the time of high input (charge) and much at the time of high output (discharge). Can accept lithium ions. For example, the (101) plane or the (104) plane other than the (003) plane may be oriented along the surface of the positive electrode layer 18. For details of the above-mentioned particles, refer to Japanese Patent No. 4745463.

The negative electrode layer 22 is composed of only the negative electrode active material. Examples of the negative electrode active material include oxide-based materials, such as Li ₄ Ti ₅ O ₁₂ (simply referred to as LTO) or TiO ₂ . In this case, the negative electrode layer 22 can be formed by sintering only the negative electrode active material.

In general, LTO has a low volume change of 0.2% due to insertion / desorption of lithium ions, so it can be said that LTO is an optimal material for all-solid-state batteries in which it is essential to maintain stable adhesion at the solid-solid interface. On the other hand, since LTO is an insulating material, practical battery performance cannot be obtained unless a conductive additive is mixed when used as an electrode material.

In addition, since LTO has a high potential with respect to lithium ions of 1.5 V, when used as an electrode material, the battery has a low energy density. There is a problem that the energy density is further reduced by adding a material (conducting aid) other than the active material (substance involved in the electrochemical reaction in the battery).

On the other hand, as described above, in the present embodiment, by using a sintered plate of LTO as the negative electrode layer 22, the electrode material is only the negative electrode active material, the filling rate of the negative electrode active material is increased, and sintering is performed. The generation of a neck (network) between particles can ensure electron conductivity without mixing a conductive additive, and can suppress a reduction in energy density.

Other examples of the negative electrode active material include graphite, soft carbon, hard carbon, carbon nanotube, and graphene.

As the lithium ion conductive material constituting the solid electrolyte layer 14, a garnet-based, nitride-based, perovskite-based, phosphoric acid-based, sulfide-based or polymer-based material can be preferably used. In this embodiment, it has a garnet-based or garnet-like crystal structure containing Li (lithium), La (lanthanum), Zr (zirconium), and O (oxygen). Specifically, a garnet-type crystal structure containing, for example, Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ) can be used as the lithium ion conductive material.

Here, an example of the manufacturing method of the positive electrode layer 18, the negative electrode layer 22, and the solid electrolyte layer 14 mentioned above is demonstrated.

[Positive electrode layer 18]
First, a green sheet having a thickness of 20 μm or less containing NiO powder, Co ₃ O ₄ powder, and Al ₂ O ₃ powder is formed, and this green sheet is formed at a temperature within the range of 1000 ° C. to 1400 ° C. in the atmosphere By firing for a predetermined time, an independent film-like sheet (self-supporting film) composed of a number of (h00) -oriented plate-like (Ni, Co, Al) O particles is formed. Here, by adding MnO ₂ , ZnO or the like as an auxiliary agent, grain growth is promoted, and as a result, the (h00) orientation of the plate-like crystal grains can be enhanced.

Here, an “independent” sheet refers to a sheet that can be handled independently from another support after firing. That is, the “independent” sheet does not include a sheet that is fixed to another support (substrate or the like) by firing and integrated with the support (unseparable or difficult to separate).

In the green sheet thus formed in a self-supporting film shape, the amount of material existing in the thickness direction is extremely small compared to the plate surface direction, that is, the in-plane direction (direction perpendicular to the thickness direction).

Therefore, in the initial stage where there are a plurality of grains in the thickness direction, grains grow in random directions. On the other hand, when the grain growth proceeds and the material in the thickness direction is consumed, the grain growth direction is limited to the in-plane two-dimensional direction. This reliably promotes grain growth in the surface direction.

In particular, by forming the green sheet as thin as possible (for example, several μm or less), or by promoting the grain growth as much as possible even if the thickness is about 100 μm (for example, about 20 μm). The grain growth in the surface direction is more reliably promoted. That is, the grain growth in the plane direction of the grains parallel to the plate surface direction, that is, the in-plane direction (direction orthogonal to the thickness direction) is promoted preferentially.

Therefore, by firing the green sheet formed in a film shape as described above, a large number of thin plate-like particles oriented so that a specific crystal plane is parallel to the plate surface of the particles are formed at the grain boundary portion. A free-standing film bonded in the plane direction can be obtained. That is, a self-supporting film is formed so that the number of crystal grains in the thickness direction is substantially one. Here, the meaning of “substantially one crystal grain in the thickness direction” does not exclude that a part (for example, end portions) of crystal grains adjacent in the plane direction overlap each other in the thickness direction. This self-supporting film can be a dense ceramic sheet in which a large number of thin plate-like particles as described above are bonded without gaps.

The (h00) -oriented (Ni, Co, Al) O ceramic sheet obtained by the above-mentioned process and lithium nitrate (LiNO ₃ ) are mixed and heated for a predetermined time, thereby (Ni, Co, Al). ) Lithium is introduced into the O particles. Thereby, the Li (Ni _0.75 Co _0.2 Al _0.05 ) for the film-like positive electrode layer 18 in which the (003) plane is oriented in the direction from the positive electrode layer 18 to the negative electrode layer 22 and the (104) plane is oriented along the plate surface. An O ₂ sheet is obtained.

[Negative electrode layer 22]
Taking an oxide-based material as an example of the negative electrode active material, a lithium titanium composite oxide (Li ₄ Ti ₅ O ₁₂ ) is pulverized and classified so that the particle size is 1 μm or less. Next, a molding aid, a plasticizer, a dispersant, and a solvent are added to the pulverized powder and mixed to prepare a slurry. This slurry is applied onto a polyethylene terephthalate (PET) film by a doctor blade method and then dried to produce a molded sheet (excluding the PET film) having a thickness of 62 μm. The negative electrode layer 22 can be produced by punching this molded sheet into a rectangular shape and performing a heat treatment at 780 ° C. in the atmosphere.

[Lithium ion conductive material of solid electrolyte layer 14]
First, in the first firing step, a raw material containing a Li component, a La component and a Zr component is fired to obtain a primary fired powder for ceramic synthesis containing Li, La, Zr and oxygen. Li ₂ CO ₃ or LiOH can be used as the Li component, La (OH) ₃ or La ₂ O ₃ can be used as the La component, and ZrO ₂ can be used as the Zr component. The first firing step is a step of obtaining a primary fired powder for facilitating the thermal decomposition of at least the Li component and the La component to easily form the LLZ crystal structure in the second firing step. The primary fired powder may already have an LLZ crystal structure. The firing temperature is preferably 850 ° C. or higher and 1150 ° C. or lower.

Thereafter, in the second firing step, the primary fired powder obtained in the first firing step is fired at a temperature of 950 ° C. to 1250 ° C., and a garnet-type or garnet-like crystal containing Li, La, Zr, and oxygen A ceramic powder having a structure is synthesized. Thereby, it is possible to easily obtain a ceramic powder or sintered body having a LLZ crystal structure and having sinterability (density) and conductivity that contains aluminum and can be handled. The second firing step may be carried out after forming the primary fired powder into a molded body having a desired three-dimensional shape (for example, a shape and size that can be used as a solid electrolyte of an all-solid secondary battery). preferable. By using a molded body, a solid phase reaction is promoted and a sintered body can be obtained. In addition, after the second firing step, the ceramic powder obtained in the second firing step may be used as a compact, and the compact may be separately subjected to a sintering step at a temperature similar to the heating temperature in the second firing step. Through these steps, the solid electrolyte layer 14 having an LLZ crystal structure can be obtained. By performing one or both of the first firing step and the second firing step in the presence of the aluminum (Al) -containing compound, the solid electrolyte layer 14 having sinterability (density) and conductivity that can be handled. It is good.

Further, as a method of forming the solid electrolyte layer 14, various particle jet coating methods, solid phase methods, solution methods, gas phase methods, and direct bonding (direct bonding) methods can be used. Examples of the particle jet coating method include an aerosol deposition (AD) method, a gas deposition (GD) method, a powder jet deposition (PJD) method, a cold spray (CS) method, and a thermal spraying method. Among these, the aerosol deposition (AD) method is particularly preferable because it can form a film at room temperature, and does not cause a composition shift during the process or formation of a high resistance layer due to a reaction with the positive electrode plate. Examples of the solid phase method include a tape lamination method and a printing method. Among these, the tape lamination method is preferable because the solid electrolyte layer 14 can be formed thin and the thickness can be easily controlled. Examples of the solution method include a hydrothermal synthesis method, a sol-gel method, a precipitation method, a microemulsion method, and a solvent evaporation method. Among these methods, the hydrothermal synthesis method is particularly preferable in that it is easy to obtain crystal grains having high crystallinity at a low temperature. In addition, microcrystals synthesized using these methods may be deposited on the positive electrode or may be directly deposited on the positive electrode. Examples of the gas phase method include laser deposition (PLD) method, sputtering method, evaporation condensation (PVD) method, gas phase reaction method (CVD) method, vacuum deposition method, molecular beam epitaxy (MBE) method and the like. Among these, the laser deposition (PLD) method is particularly preferable because there is little composition deviation and a film with relatively high crystallinity can be easily obtained. The direct bonding (direct bonding) method is a method in which the solid electrolyte layer 14 and the positive electrode plate, which are formed in advance, are chemically activated and bonded at a low temperature. For activation of the interface, plasma or the like may be used, or chemical modification of a functional group such as a hydroxyl group may be used.

The example of the constituent material of the positive electrode layer 18 and the negative electrode layer 22 described above is a preferable aspect in which the energy density is suppressed, but other constituent materials shown below may be used.

That is, the positive electrode layer 18 may be configured by mixing a positive electrode active material, a solid electrolyte material, and a conductive additive, and compacting them.

In this case, the positive electrode active material is, for example, a general formula: Li _p (Ni _x Co _y Al _z ) O ₂
(In the above general formula, 0.9 ≦ p ≦ 1.3, 0.6 <x <0.9, 0.1 <y ≦ 0.3, 0 ≦ z ≦ 0.2, x + y + z = 1)
The solid electrolyte material has a garnet-type crystal structure including, for example, Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ), and the conductive additive is, for example, acetylene black. Also good.

The negative electrode layer 22 may be configured by mixing a negative electrode active material and a solid electrolyte material and compacting them. In this case, the negative electrode active material is, for example, graphite, and the solid electrolyte material may have a garnet-type crystal structure including, for example, Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ).

The all-solid-state battery according to the present invention is not limited to the above-described embodiment, and can of course have various configurations without departing from the gist of the present invention.

Claims

Solid electrolyte layer (14), positive electrode side current collector (16), positive electrode layer (18) connected to positive electrode side current collector (16), negative electrode side current collector (20), and negative electrode A negative electrode layer (22) connected to the side current collector (20),
The positive electrode layer (18) and the negative electrode layer (22) are alternately stacked,
Between the positive electrode layer (18) and the negative electrode layer (22), between the positive electrode layer (18) and the negative electrode side current collector (20), and between the negative electrode layer (22) and the positive electrode side current collector. The solid electrolyte layer (14) is interposed between the solid electrolyte layer (16) and the all solid state battery.
The all-solid-state battery according to claim 1,
The all-solid-state battery, wherein the positive electrode side current collector (16) and the negative electrode side current collector (20) face each other.
In the all-solid-state battery of Claim 1 or 2,
The negative electrode layer (22) has a first negative electrode layer (22a) and a second negative electrode layer (22b),
The first negative electrode layer (22a), the positive electrode layer (18), and the second negative electrode layer (22b) are alternately stacked,
The solid electrolyte layer (14)
A first solid electrolyte layer (14a) interposed between the positive current collector (16) and the first negative electrode layer (22a);
Interposed between the positive electrode side current collector (16) and the negative electrode side current collector (20) and between the first negative electrode layer (22a) and the positive electrode layer (18). A second solid electrolyte layer (14b);
A third solid electrolyte layer (14c) interposed between the positive electrode layer (18) and the negative electrode side current collector (20);
Between the positive electrode side current collector (16) and the negative electrode side current collector (20), and interposed between the second negative electrode layer (22b) and the positive electrode layer (18). A fourth solid electrolyte layer (14d);
An all solid state battery comprising a fifth solid electrolyte layer (14e) interposed between the positive electrode side current collector (16) and the second negative electrode layer (22b).
The all solid state battery according to any one of claims 1 to 3,
The lithium ion conductive material constituting the solid electrolyte layer (14) is composed of a garnet-based, nitride-based, perovskite-based, phosphoric acid-based, sulfide-based or polymer-based material. All solid battery.
The all solid state battery according to any one of claims 1 to 4,
The all-solid-state battery, wherein the positive electrode layer (18) is composed of only a positive electrode active material having a specific crystal plane oriented in a lithium ion conduction direction.
The all-solid-state battery according to claim 5,
The all-solid-state battery, wherein the positive electrode active material has a layered rock salt structure or a spinel structure.
The all-solid-state battery according to claim 6,
The positive electrode active material is
General formula: Li p (Ni x Co y Al z ) O 2
(In the above general formula, 0.9 ≦ p ≦ 1.3, 0.6 <x <0.9, 0.1 <y ≦ 0.3, 0 ≦ z ≦ 0.2, x + y + z = 1)
It has a layered rock salt structure represented by
The all-solid-state battery, wherein the specific crystal plane is a (003) plane.
The all solid state battery according to any one of claims 1 to 4,
The positive electrode layer (18) is an all-solid battery characterized in that a positive electrode active material, a solid electrolyte material, and a conductive additive are mixed and compacted.
The all-solid-state battery according to claim 8,
The positive electrode active material is
General formula: Li p (Ni x Co y Al z ) O 2
(In the above general formula, 0.9 ≦ p ≦ 1.3, 0.6 <x <0.9, 0.1 <y ≦ 0.3, 0 ≦ z ≦ 0.2, x + y + z = 1)
It has a layered rock salt structure represented by
The solid electrolyte material has a garnet-based crystal structure including Li 7 La 3 Zr 2 O 12 (LLZ),
The all-solid-state battery, wherein the conductive assistant is acetylene black.
The all solid state battery according to any one of claims 1 to 9,
The said negative electrode layer (22) is comprised only with the negative electrode active material, The all-solid-state battery characterized by the above-mentioned.
The all-solid-state battery according to claim 10,
The all-solid-state battery, wherein the negative electrode active material is an oxide-based material.
The all-solid-state battery according to claim 11,
The all-solid-state battery, wherein the negative electrode active material is Li 4 Ti 5 O 12 or TiO 2 .
The all-solid-state battery according to claim 10,
The all-solid-state battery, wherein the negative electrode active material is a carbon-based material.
The all-solid-state battery according to claim 13,
The all-solid-state battery, wherein the negative electrode active material is graphite, soft carbon, hard carbon, carbon nanotube, or graphene.
The all solid state battery according to any one of claims 1 to 9,
The said negative electrode layer (22) mixes a negative electrode active material and a solid electrolyte material, and is compacted and comprised, The all-solid-state battery characterized by the above-mentioned.
The all-solid-state battery according to claim 15,
The negative electrode active material is graphite,
The all-solid-state battery, wherein the solid electrolyte material has a garnet-type crystal structure containing Li 7 La 3 Zr 2 O 12 (LLZ).
An all-solid battery comprising a plurality of unit cells (12) laminated,
The single cell (12)
Solid electrolyte layer (14), positive electrode side current collector (16), positive electrode layer (18) connected to positive electrode side current collector (16), negative electrode side current collector (20), and negative electrode A negative electrode layer (22) connected to the side current collector (20),
The positive electrode layer (18) and the negative electrode layer (22) are alternately stacked,
Between the positive electrode layer (18) and the negative electrode layer (22), between the positive electrode layer (18) and the negative electrode side current collector (20), and between the negative electrode layer (22) and the positive electrode side current collector. The solid electrolyte layer (14) is interposed between the solid electrolyte layer (16) and the all solid state battery.
The all-solid-state battery according to claim 17,
An all-solid-state battery, wherein an insulating layer (24) is interposed between at least one adjacent single cell (12) among the plurality of single cells (12) arranged in the stacking direction.
The all-solid-state battery according to claim 17,
An all-solid-state battery, wherein an insulating layer (24) is interposed between at least one adjacent single cell (12) among the plurality of single cells (12) arranged in the lateral direction.
The all-solid-state battery according to claim 17,
All solids characterized by having current collector plates (30) connected to the negative electrode side current collector (20) or the positive electrode side current collector (16) on both end faces of each single cell (12). battery.
The all-solid-state battery according to claim 17,
An all-solid-state battery, wherein a current collector (26) is interposed between the single cells (12) arranged in the lateral direction.