JP2016033880A - All-solid lithium battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an all-solid lithium battery which has a structure suitable for enhancement of humidity resistance as well as capacity and energy density, and enables the significant suppression of battery characteristic degradation (especially, the decline in discharge capacity) owing to the repetition of charge/discharge.SOLUTION: An all-solid lithium battery comprises: a positive electrode plate composed of an oriented polycrystalline material in which lithium transition metal oxide particles are oriented; a solid electrolytic layer including a lithium ion-conducting material; a negative electrode layer; a metal positive electrode sheath material covering the positive electrode plate from outside; a metal negative electrode sheath material covering the negative electrode layer from outside; and a seal part including a sealing material for sealing exposed parts of the positive electrode plate, the solid electrolytic layer and the negative electrode layer which are not covered with the positive electrode sheath material or the negative electrode sheath material. The positive electrode plate has a thickness of 15-60 μm. The ratio of the positive electrode plate thickness tto negative electrode layer's thickness tis 1≤t/t≤15. The oriented polycrystalline material has an orientation degree of 10% or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an all solid lithium battery.

  In recent years, with the development of portable devices such as personal computers and mobile phones, the demand for batteries as power sources has been greatly expanded. 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 intrinsic safety, 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.

For example, Patent Document 1 (Japanese Patent Laid-Open No. 2013-105708) includes a positive electrode layer made of lithium cobaltate (LiCoO ₂ ), a negative electrode layer made of metallic lithium, and a lithium phosphate oxynitride glass electrolyte (LiPON). A thin film lithium secondary battery including a solid electrolyte layer that can be formed is disclosed, and it is described that a positive electrode layer is formed by sputtering and has a thickness in the range of 1 to 15 μm. In addition, an all-solid battery has been proposed in which the positive electrode is made thicker to try to improve the capacity. For example, Patent Document 2 (Japanese Patent Publication No. 2009-516359) discloses a positive electrode having a thickness greater than about 4 μm and less than about 200 μm, a solid electrolyte having a thickness of less than about 10 μm, and a negative electrode having a thickness of less than about 30 μm. An all-solid battery is disclosed. In these documents, there is no description that the positive electrode active material is oriented.

On the other hand, an oriented sintered body plate of a lithium composite oxide has been proposed. For example, Patent Document 3 (Japanese Patent Laid-Open No. 2012-009193) and Patent Document 4 (Japanese Patent Laid-Open No. 2012-009194) have a layered rock salt structure, and have X-ray diffraction with respect to the diffraction intensity by the (104) plane. A lithium composite oxide sintered plate having a diffraction intensity ratio [003] / [104] of (003) plane of 2 or less is disclosed. Patent Document 5 (Japanese Patent No. 4745463) discloses a general formula: Li _p (Ni _x , Co _y , Al _z ) O ₂ (where 0.9 ≦ p ≦ 1.3, 0.6 < x ≦ 0.9, 0.1 <y ≦ 0.3, 0 ≦ z ≦ 0.2, x + y + z = 1) and a plate-like particle having a layered rock salt structure is disclosed, and (003) plane Is oriented so as to intersect the plate surface of the particles.

Further, as a solid electrolyte having lithium ion conductivity, a garnet-type ceramic material having a composition of a Li—La—Zr—O-based composite oxide (hereinafter referred to as LLZ) typified by Li ₇ La ₃ Zr ₂ O ₁₂ Is attracting attention. For example, Patent Document 6 (Japanese Patent Laid-Open No. 2011-051800) discloses that the addition of Al in addition to Li, La and Zr, which are basic elements of LLZ, can improve the denseness and lithium ion conductivity. ing. Patent Document 7 (Japanese Patent Laid-Open No. 2011-073962) discloses that lithium ion conductivity can be further improved by adding Nb and / or Ta in addition to Li, La, and Zr, which are basic elements of LLZ. ing. Patent Document 8 (Japanese Patent Application Laid-Open No. 2011-073963) includes Li, La, Zr, and Al, and the density can be further improved by setting the molar ratio of Li to La to 2.0 to 2.5. Is disclosed.

By the way, in an all-solid-state lithium battery, a technique is known in which battery constituent members are sealed with a sealing material to improve moisture resistance, thereby improving battery performance. For example, Patent Document 9 (Japanese Patent Laid-Open No. 2009-158476) discloses an all-solid lithium secondary battery including sealing the periphery of an all-solid lithium secondary battery element with a low-melting glass having a softening temperature of 350 ° C. or lower. A battery manufacturing method has been proposed, and it is considered preferable to use a glass composed of four components of V ₂ O ₅ , ZnO, BaO and TeO ₂ as the low melting point glass.

JP 2013-105708 A Special table 2009-516359 gazette JP 2012-009193 A JP 2012-009194 A Japanese Patent No. 4745463 JP 2011-051800 A JP 2011-073962 A JP 2011-073963 A JP 2009-158476 A

  However, the all-solid-state lithium battery disclosed in Patent Document 9 uses a highly solid sulfur-based solid electrolyte as an electrolyte, and the electrode layer is a mixture of such a solid electrolyte and an electrode active material. It consists of For this reason, the reaction between the electrode active material and the solid electrolyte proceeds due to the heating at the time of sealing the glass, and the desired capacity and cycle characteristics cannot be obtained (for example, the discharge capacity decreases with repeated charge / discharge). There is.

The present inventors have recently used a positive electrode plate made of an oriented polycrystal in an all-solid lithium battery, and the thickness of the positive electrode plate, the degree of orientation of the positive electrode plate, and the thickness t _{P of the} positive electrode plate By controlling the ratio t _P / t _N of the thickness t _N of the negative electrode layer within a predetermined range, the structure is suitable not only for the capacity and energy density but also for improving the moisture resistance, but with repeated charging and discharging. The present inventors have found that deterioration of battery characteristics (particularly, reduction in discharge capacity) can be significantly suppressed.

  Accordingly, the object of the present invention is to not only reduce the capacity and energy density but also improve the moisture resistance, and can significantly suppress the deterioration of battery characteristics (particularly the reduction of discharge capacity) due to repeated charge and discharge. The object is to provide an all-solid-state lithium battery.

According to one aspect of the present invention, a positive electrode plate composed of an oriented polycrystalline body in which a plurality of lithium transition metal oxide particles are oriented;
A solid electrolyte layer provided on the positive electrode plate and made of a lithium ion conductive material;
A negative electrode layer provided on the solid electrolyte layer;
A metal positive electrode exterior material that covers the outside of the positive electrode plate and also functions as a positive electrode current collector;
A metal negative electrode exterior material that covers the outside of the negative electrode layer and also functions as a negative electrode current collector;
A sealing portion made of a sealing material that seals the exposed portion of the positive electrode plate, the solid electrolyte layer, and the negative electrode layer, which is not covered with the positive electrode exterior material and the negative electrode exterior material;
An all-solid-state lithium battery comprising:
The thickness of the positive electrode plate is 15 to 60 μm, and the ratio of the thickness t _P of the positive electrode plate to the thickness t _N of the negative electrode layer is 1 ≦ t _P / t _N ≦ 15,
An all solid lithium battery is provided in which the oriented polycrystal has an orientation degree of 10% or more.

It is a schematic cross section which shows an example of the all-solid-state lithium battery of this invention. It is a schematic diagram which shows the structure of the aerosol deposition (AD) film-forming apparatus used in the Example.

An example of the all-solid lithium battery according to the invention is shown schematically in all-solid-state lithium batteries Figure 1. The all-solid lithium battery 10 shown in FIG. 1 includes a positive electrode plate 12, a solid electrolyte layer 14, a negative electrode layer 16, a positive electrode exterior material 13, a negative electrode exterior material 17, and a sealing portion 18. The positive electrode plate 12 is composed of an oriented polycrystal formed by aligning a plurality of lithium transition metal oxide particles. The solid electrolyte layer 14 is provided on the positive electrode plate 12 and is made of a lithium ion conductive material. The negative electrode layer 16 is provided on the solid electrolyte layer 14. The positive electrode exterior member 13 is a metal member that covers the outer side of the positive electrode plate 12 and also functions as a positive electrode current collector. The negative electrode exterior member 17 is a metal member that covers the outer side of the negative electrode layer 16 and also functions as a negative electrode current collector. The sealing portion 18 is a portion made of a sealing material that seals the exposed portions of the positive electrode plate 12, the solid electrolyte layer 14, and the negative electrode layer 16 that are not covered with the positive electrode exterior material 13 and the negative electrode exterior material 17. is there. The thickness of the positive electrode plate 12 is 15 to 60 μm, the ratio of the thickness t _P of the positive electrode plate 12 and the thickness t _N of the negative electrode layer 16 is 1 ≦ t _P / t _N ≦ 15, and the oriented polycrystal The body has an orientation degree of 10% or more. According to the all-solid-state lithium battery having such a configuration, although it is a configuration suitable for improving not only capacity and energy density but also moisture resistance, deterioration of battery characteristics due to repeated charge / discharge (especially reduction of discharge capacity) Can be significantly suppressed.

  Each composition of the positive electrode plate 12 and the solid electrolyte layer 14 is known to improve battery characteristics as described in, for example, Patent Documents 3 to 8. However, in the present invention, the positive electrode plate 12 is composed of an oriented polycrystal, and the thickness is increased to 15 μm or more. In this regard, a positive electrode layer having a thickness of 10 μm or more is not known as in Patent Documents 1 and 2, but the capacity and energy density are increased as expected only by forming the positive electrode layer to be thick. Cannot be obtained. This is considered to be because, in the case of a conventional positive electrode layer in which the positive electrode active material is not oriented, it is difficult to efficiently remove and insert lithium ions over the entire thickness of the thick positive electrode layer. For example, it may happen that lithium existing on the side of the thick positive electrode layer away from the solid electrolyte cannot be sufficiently extracted. In this respect, since the positive electrode plate 12 used in the present invention is an oriented polycrystal composed of a plurality of lithium transition metal oxide particles oriented in a certain direction, even if the positive electrode active material is provided thick, the thickness of the positive electrode plate It is easy to remove and insert high-efficiency lithium ions throughout, and the capacity improvement effect brought about by the thick positive electrode active material can be maximized. For example, lithium existing on the side of the thick positive electrode plate away from the solid electrolyte can be sufficiently extracted. Such an increase in capacity can greatly improve the energy density of the all-solid-state battery. That is, according to the all solid lithium battery of the present invention, battery performance with high capacity and energy density can be obtained. Therefore, it is possible to realize a highly safe all-solid battery having a high capacity and a high energy density while being relatively thin or small. In particular, since the positive electrode plate 12 can be composed of a ceramic sintered body, it can be easily formed thicker than a film formed by a vapor phase method such as sputtering, and the composition is accurately controlled by strictly weighing the raw material powder. There is also an advantage that it is easy to do.

In addition, the sealing portion 18 is provided to seal the exposed portions of the positive electrode plate 12, the solid electrolyte layer 14, and the negative electrode layer 16 that are not covered with the positive electrode outer packaging material 13 and the negative electrode outer packaging material 17. Moisture resistance (desirably moisture resistance at high temperature) can be ensured. Thereby, it is possible to effectively prevent undesirable moisture from entering the all solid lithium battery 10 and improve battery characteristics. Nevertheless, in an all-solid lithium battery in which the electrode layer is composed of a mixture of an electrode active material and a (very active) sulfur-based solid electrolyte, as disclosed in Patent Document 9, glass sealing The reaction between the electrode active material and the solid electrolyte progresses due to heating, and the desired capacity and cycle characteristics cannot be obtained (for example, the discharge capacity decreases with repeated charge and discharge). Just as you did. In this respect, by using a solid electrolyte other than sulfur-based, avoiding the use of a sealing material that requires bonding at a relatively high temperature such as glass sealing, or by increasing the thickness of the electrode, Although the above problem seemed to be solved, the present inventors have found that this is not the case. Thus, it is important to control the thickness of the positive electrode plate, the degree of orientation of the positive electrode plate, and the ratio t _P / t _N of the positive electrode plate thickness t _P and the negative electrode layer thickness t _N within a predetermined range. The present inventors have found out. Specifically, in the all solid lithium battery 10 of the present invention, the thickness of the positive electrode plate 12 is 15 to 60 μm, and the ratio of the thickness t _P of the positive electrode plate 12 to the thickness t _N of the negative electrode layer 16 is 1 ≦ t _P / t _N ≦ 15, and the oriented polycrystal has an orientation degree of 10% or more. By satisfying these various conditions, unexpectedly, deterioration of battery characteristics (particularly, reduction in discharge capacity) associated with repeated charge / discharge can be significantly suppressed. Although this mechanism is not clear, it is thought that various factors acted favorably with the control of the above conditions.

The positive electrode plate 12 is composed of an oriented polycrystal formed by aligning a plurality of lithium transition metal oxide particles. That is, the particles constituting the positive electrode plate 12 or the oriented polycrystal are composed of a lithium transition metal oxide. The lithium transition metal oxide preferably has a layered rock salt structure or a spinel structure, and more preferably has a layered rock salt structure. The layered rock salt structure has the property that the redox potential decreases due to occlusion of lithium ions, and the redox potential increases due to elimination of lithium ions. Here, the layered rock salt structure is a crystal structure in which transition metal layers other than lithium and lithium layers are alternately stacked with an oxygen atom layer interposed therebetween, that is, an ion layer and lithium ions of transition metals other than lithium. Crystal structure in which layers are alternately stacked with oxide ions in between (typically α-NaFeO ₂ type structure: structure in which transition metal and lithium are regularly arranged in the [111] axis direction of cubic rock salt type structure ). Typical examples of the lithium-transition metal composite oxide having a layered rock salt structure include lithium nickelate, lithium manganate, nickel / lithium manganate, nickel / lithium cobaltate, cobalt / nickel / lithium manganate, cobalt / manganese. Examples of these materials include Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ag, Sn, and the like. One or more elements such as Sb, Te, Ba, Bi and the like may be further included.

That is, the lithium transition metal oxide particles are Li _x M1O ₂ or Li _x (M1, M2) O ₂ (where 0.5 <x <1.10, M1 is selected from the group consisting of Ni, Mn and Co) At least one kind of transition metal element, M2 is Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ag, Sn, Sb , Te, Ba, and Bi), and is more preferably represented by Li _x (M1, M2) O ₂ , and M1 is Ni. And M2 is a composition that is at least one selected from the group consisting of Mg, Al and Zr, more preferably Li _x (M1, M2) O ₂ , and M1 is Ni and Co. M2 is Al It is. The proportion of Ni in the total amount of M1 and M2 is preferably 0.6 or more in atomic ratio. Any of such compositions can take a layered rock salt structure. A ceramic having a Li _x (Ni, Co, Al) O ₂ -based composition in which M1 is Ni and Co and M2 is Al may be referred to as NCA ceramics. Particularly preferred NCA ceramics have the general formula: Li _p (Ni _x , Co _y , Al _z ) O ₂ (where 0.9 ≦ p ≦ 1.3, 0.6 <x ≦ 0.9, 0.1 <Y ≦ 0.3, 0 ≦ z ≦ 0.2, x + y + z = 1), and has a layered rock salt structure. Further, the composition is represented by Li _x M1O ₂ and M1 is Ni, Mn, and Co, or M1 is represented by Li _x M1O ₂ that is Co, and M1 is Ni, Mn, and Co, or M1 Also preferred is a lithium transition metal oxide having a composition in which is Co.

  As described above, the positive electrode plate 12 is made of an oriented polycrystalline body made of a plurality of lithium transition metal oxide particles. This oriented polycrystal is preferably composed of a plurality of lithium transition metal oxide particles oriented in a certain direction. The certain direction is preferably a lithium ion conduction direction. Typically, a specific crystal plane of each particle constituting the positive electrode plate 12 is oriented in a direction from the positive electrode plate 12 toward the negative electrode layer 16. Become. The lithium transition metal oxide particles are preferably particles formed in a plate shape with a thickness of about 2 to 100 μm. 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 plate 12 toward the negative electrode layer 16. Thereby, it does not become a resistance at the time of insertion / removal of the lithium ion with respect to the positive electrode plate 12, but can release many 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 plate surface of the positive electrode plate 12. Patent Documents 3 to 5 can be referred to for details of the above-described particles and oriented polycrystals, and the disclosure of these documents is incorporated herein by reference.

（上記式中、Ｉは正極板試料の回折強度であり、Ｉ_０は無配向の参照試料の回折強度である。（ＨＫＬ）は配向度を評価したい回折線であり、（００ｌ）（ｌは例えば３、６及び９である）以外の回折線に相当にする。（ｈｋｌ）は全ての回折線に相当する。） The oriented polycrystal has an orientation degree of 10% or more, preferably 15 to 95%, for example 15 to 85%. More specifically, the degree of orientation is 10% or more, preferably 20% or more, more preferably 30% or more, still more preferably 40% or more, and particularly preferably 50% or more with respect to the lower limit. The upper limit of the degree of orientation should not be particularly limited, but may be, for example, 95% or less, 90% or less, 85% or less, 80% or less, 75% or less, or 70% or less. In addition, this degree of orientation uses the plate | board surface of the positive electrode plate 12 as a sample surface, and uses the XRD apparatus (For example, Rigaku Co., Ltd. product, TTR-III), X-ray diffraction is 2 (theta) in the range of 10 degrees-70 degrees. The degree of orientation may be calculated based on the following formula using the obtained XRD profile according to the Lotgering method, under the conditions of 2 ° / min and a step width of 0.02 °.

(In the above formula, I is the diffraction intensity of the positive electrode plate sample, I ₀ is the diffraction intensity of the non-oriented reference sample. (HKL) is the diffraction line for which the degree of orientation is to be evaluated, and (00l) (l is (For example, 3, 6 and 9.) (hkl) corresponds to all diffraction lines.)

  The non-oriented reference sample is a sample having the same configuration as the positive electrode plate sample except that it is non-oriented. For example, the non-oriented reference sample can be obtained by pulverizing the positive electrode plate sample with a mortar to make it non-oriented. . In the above formula, with respect to (HKL), the (001) diffraction line is removed because the plane corresponding to this diffraction line (for example, the (003) plane) is the in-plane direction (the direction parallel to the plane). This is because the movement of lithium ions is hindered when the surface is oriented along the plate surface of the positive electrode plate 12. Therefore, the plurality of lithium transition metal oxide particles are preferably oriented in a direction such that a specific crystal plane of the particles intersects the plate surface of the positive electrode plate. In particular, the lithium transition metal oxide particles have a layered rock salt structure, and the specific crystal plane is the (003) plane, that is, the (003) plane of the layered rock salt structure intersects the plate plane of the positive electrode plate 12. It is preferably oriented in the direction. That is, the direction that intersects the plate surface of the positive electrode plate 12 is the lithium ion conduction direction. According to this configuration, the (003) surface of each particle constituting the positive electrode plate 12 extends from the positive electrode plate 12 to the negative electrode layer. It will be oriented in the direction towards 16.

The thickness of the positive electrode plate 12 is 15 to 60 μm, more preferably 20 to 40 μm, but the ratio t _P / t _N of the thickness t _P of the positive electrode plate 12 and the thickness t _N of the negative electrode layer 16 is 1 to 15, More preferably, it should be 2-6. As described above, the oriented polycrystalline body constituting the positive electrode plate 12 is suitable for making it thicker than the non-oriented polycrystalline body. If the thickness satisfies the above conditions, not only can the active material capacity per unit area be increased, but it can also significantly suppress deterioration of battery characteristics (particularly reduction in discharge capacity) due to repeated charge and discharge. it can.

  The positive electrode plate 12 is preferably formed in a sheet shape. A preferred method for producing a positive electrode active material (hereinafter referred to as a positive electrode active material sheet) formed in the form of a sheet will be described later. The positive electrode plate 12 may be constituted by one positive electrode active material sheet, or the positive electrode plate 12 may be constituted by arranging a plurality of small pieces obtained by dividing the positive electrode active material sheet in layers. Good.

  The oriented polycrystalline body constituting the positive electrode plate 12 preferably has a relative density of 75 to 99.97%, more preferably 80 to 99.95%, still more preferably 90 to 99.90%, and particularly preferably 95. It has a relative density of ˜99.88%, most preferably 97-99.85%. From the viewpoint of capacity and energy density, it is basically desirable that the relative density be high, but if it is within the above range, the resistance value is unlikely to increase even after repeated charge and discharge. It is thought that this is because the positive electrode plate 12 can be appropriately expanded and contracted as lithium is deinserted and the stress can be relieved by the relative density.

The lithium ion conductive material constituting the solid electrolyte layer 14 is a garnet ceramic material, a nitride ceramic material, a perovskite ceramic material, a phosphate ceramic material, a sulfide ceramic material, or a polymer material. Preferably, it is at least one selected from the group consisting of garnet-based ceramic materials, nitride-based ceramic materials, perovskite-based ceramic materials, and phosphate-based ceramic materials. Examples of garnet ceramic material, Li-La-Zr-O-based material _{(specifically,} such as _{Li 7 La 3 Zr 2 O 12} ), the Li-La-Ta-O-based material (specifically, Li ₇ La ₃ Ta ₂ O ₁₂ etc.). An example of a nitride ceramic material is Li ₃ N. Examples of the perovskite-based ceramic material include Li-La-Zr-O-based materials (specifically, LiLa _1-x Ti _x O ₃ (0.04 ≦ x ≦ 0.14) and the like). Examples of phosphate ceramic materials include lithium phosphate, nitrogen-substituted lithium phosphate (LiPON), Li-Al-Ti-PO, Li-Al-Ge-PO, and Li-Al-Ti-. Si—P—O (specifically, Li _{1 + x + y} Al _x Ti _2−x Si _y P _3−y O ₁₂ (0 ≦ x ≦ 0.4, 0 <y ≦ 0.6), etc.) may be mentioned.

The lithium ion conductive material constituting the solid electrolyte layer 14 is particularly preferably composed of a Li—La—Zr—O based ceramic material and / or a lithium phosphate oxynitride (LiPON) based ceramic material. The Li-La-Zr-O-based material is an oxide sintered body having a garnet-type or garnet-type similar crystal structure including Li, La, Zr, and O, specifically, Li ₇ A garnet-based ceramic material such as La ₃ Zr ₂ O ₁₂ . As such materials, those described in Patent Documents 6 to 8 can be used, and the disclosure content of these documents is incorporated herein by reference. The garnet-based ceramic material is a lithium ion conductive material that does not react even when directly contacted with the negative electrode lithium, and in particular, a garnet-type or garnet-type similar crystal structure including Li, La, Zr, and O Oxide sintered bodies having excellent sinterability and easy densification and high ionic conductivity. A garnet-type or garnet-like crystal structure having this kind of composition is called an LLZ crystal structure, which is referred to as CSD (Cambridge Structure Database) X-ray diffraction file No. It has an XRD pattern similar to 422259 (Li ₇ La ₃ Zr ₂ O ₁₂ ). In addition, No. Compared to 422259, the constituent elements are different and the Li concentration in the ceramics may be different, so the diffraction angle and the diffraction intensity ratio may be different. The molar ratio Li / La of Li to La is preferably 2.0 or more and 2.5 or less, and the molar ratio Zr / La to La is preferably 0.5 or more and 0.67 or less. This garnet-type or garnet-like crystal structure may further comprise Nb and / or Ta. That is, by replacing a part of Zr of LLZ with one or both of Nb and Ta, the conductivity can be improved as compared with that before the substitution. The substitution amount (molar ratio) of Zr with Nb and / or Ta is preferably set such that the molar ratio of (Nb + Ta) / La is 0.03 or more and 0.20 or less. The garnet-based oxide sintered body preferably further contains Al, and these elements may exist in the crystal lattice or may exist in other than the crystal lattice. The addition amount of Al is preferably 0.01 to 1% by mass of the sintered body, and the molar ratio Al / La to La is preferably 0.008 to 0.12. Such LLZ-based ceramics can be produced according to a known technique as described in Patent Documents 6 to 8, or by appropriately modifying it, and the disclosure of these documents can be found in this specification. Is incorporated. A lithium phosphate oxynitride (LiPON) ceramic material is also preferable. LiPON is a group of compounds represented by the composition of Li _2.9 PO _3.3 N _0.46 . For example, Li _a PO _b N _c (wherein a is 2 to 4, b is 3 to 5 , C is 0.1 to 0.9).

  The dimension of the solid electrolyte layer 14 is not particularly limited, but the thickness is preferably 0.0005 mm to 0.5 mm, more preferably 0.001 mm to 0.1 mm, and still more preferably, from the viewpoint of charge / discharge rate characteristics and mechanical strength. Is 0.005 to 0.05 mm.

  As a method for forming the solid electrolyte layer 14, various particle jet coating methods, solid phase methods, solution methods, gas phase methods, and 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 solvothermal method, 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 surfaces of the solid electrolyte layer 14 and the positive electrode plate 12 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 interface between the positive electrode plate 12 and the solid electrolyte layer 14 may be subjected to a treatment for reducing the interface resistance. For example, such treatment includes niobium oxide, titanium oxide, tungsten oxide, tantalum oxide, lithium-nickel composite oxide, lithium-titanium composite oxide, lithium-niobium compound, lithium-tantalum compound, lithium- This can be done by coating the surface of the positive electrode plate 12 and / or the surface of the solid electrolyte layer 14 with a tungsten compound, a lithium / titanium compound, and any combination or composite oxide thereof. By such treatment, a film can exist at the interface between the positive electrode plate 12 and the solid electrolyte layer 14, and the thickness of the film is extremely thin, for example, 20 nm or less.

Negative electrode layer The negative electrode layer 16 comprises a negative electrode active material, and this negative electrode active material may be any of various known negative electrode active materials that can be used in an all solid lithium battery. Preferable examples of the negative electrode active material include lithium metal, lithium alloy, carbonaceous material, lithium titanate (LTO) and the like. Preferably, the negative electrode layer 16 may be formed by placing a negative electrode active material (for example, a lithium metal foil) in the form of a foil on the solid electrolyte layer 14 or the negative electrode current collector 15, or the solid electrolyte layer 14 or Fabricated by forming a thin layer of lithium metal or a metal alloying with lithium on the negative electrode current collector 15 by vacuum deposition, sputtering, CVD, or the like, and forming a layer of lithium metal or a metal alloying with lithium. can do.

The thickness of the positive electrode plate 12 is 15 to 60 μm, more preferably 20 to 40 μm, but the ratio t _P / t _N of the thickness t _P of the positive electrode plate 12 and the thickness t _N of the negative electrode layer 16 is 1 to 15, More preferably, it should be 2-6. As described above, when the thickness satisfies the above conditions, deterioration of battery characteristics (particularly, reduction in discharge capacity) due to repeated charge / discharge can be significantly suppressed.

It is preferable to interpose an intermediate layer between the negative electrode layer 16 and the solid electrolyte layer 14. As a constituent material of the intermediate layer, a metal alloyed with lithium, an oxide-based material, or the like can be used. In this case, charge / discharge cycle characteristics can be improved. Examples of metals alloyed with lithium include Al (aluminum), Si (silicon), Zn (zinc), Ga (gallium), Ge (germanium), Ag (silver), Au (gold), and Cd (cadmium). , In (indium), Sn (tin), Sb (antimony), Pb (lead), Bi (bismuth), and any combination thereof. The metal alloyed with lithium may be an alloy composed of two or more elements such as Mg ₂ Si and Mg ₂ Sn. Examples of the oxide material include Li ₄ Ti ₅ O ₁₂ , TiO ₂ , and SiO. The intermediate layer may be formed by a known method such as an aerosol deposition (AD) method, a pulse laser deposition (PLD) method, or a sputtering method.

The exterior material positive electrode exterior material 13 is a metal member that covers the outside of the positive electrode plate 12 and also functions as a positive electrode current collector. The negative electrode exterior member 17 is a metal member that covers the outer side of the negative electrode layer 16 and also functions as a negative electrode current collector. The positive electrode exterior material 13 and the negative electrode exterior material 17 may be made of the same or different materials, but are preferably made of the same material. The metal composing the positive electrode exterior material 13 and the negative electrode exterior material 17 is not particularly limited as long as it does not react with the positive electrode plate 12 and the negative electrode layer 16, and may be an alloy. Preferred examples of such metals include stainless steel, aluminum, copper, platinum, and nickel, and more preferably stainless steel. The positive electrode exterior material 13 and the negative electrode exterior material 17 are preferably metal plates or metal foils, and more preferably metal foils. Therefore, it can be said that the most preferable exterior material is stainless steel foil. The preferable thickness of the metal foil is 1 to 30 μm, more preferably 5 to 25 μm, and still more preferably 10 to 20 μm.

The sealing part sealing part 18 is comprised with a sealing material. The sealing material seals the exposed portions of the positive electrode plate 12, the solid electrolyte layer 14, and the negative electrode layer 16, which are not covered with the positive electrode outer packaging material 13 and the negative electrode outer packaging material 17, and has excellent moisture resistance (desirably moisture resistance at high temperature). The property is not particularly limited as long as the property can be secured. However, it goes without saying that it is desirable that the sealing material ensure electrical insulation between the positive electrode plate 12 and the negative electrode layer 16. In that sense, the sealing material preferably has a resistivity of 1 × 10 ⁶ Ωcm or more, more preferably 1 × 10 ⁷ Ωcm or more, and further preferably 1 × 10 ⁸ Ωcm or more. Such a resistivity can significantly reduce self-discharge. The width of the sealing portion 18 (also referred to as the thickness of the solid electrolyte layer 14 in the layer surface direction) is preferably 0.5 to 3 mm, more preferably 0.7 to 2 mm, and still more preferably 1 to 2 mm. .

The sealing material is preferably a glass-based sealing material containing glass. It is preferable that the glass-based sealing material contains at least one selected from the group consisting of V, Sn, Te, P, Bi, B, Zn, and Pb from the viewpoint of easily obtaining a desired softening temperature and thermal expansion coefficient. Of course, these elements may be present in the glass in the form of V ₂ O ₅ , SnO, TeO ₂ , P ₂ O ₅ , Bi ₂ O ₃ , B ₂ O ₃ , ZnO, and PbO. However, it is more preferable that the glass-based sealing material does not contain Pb or PbO which can be a harmful substance. The glass-based sealing material preferably has a softening temperature of 400 ° C. or lower, more preferably 370 ° C. or lower, and further preferably 350 ° C. or lower. The softening temperature is not particularly limited with respect to the lower limit value, but may be, for example, 300 ° C or higher, 310 ° C or higher, or 320 ° C or higher. In any case, by using the glass-based sealing material having a relatively low softening temperature in this way, the sealing portion 18 can be formed at a relatively low temperature. As a result, the sealing with heating can be performed. The resulting destruction and alteration of the battery can be effectively prevented. Further, the glass-based sealing material preferably has a thermal expansion coefficient of 7 × 10 ⁻⁶ / ° C. or more, more preferably 9 × 10 ^{−6 to} 20 × 10 ⁻⁶ / ° C., and still more preferably 10 × 10 ^{− 6 to} 19 × 10 ⁻⁶ / ° C., particularly preferably 12 × 10 ⁻⁶ to 18 × 10 ⁻⁶ / ° C., and most preferably 15 × 10 ⁻⁶ to 18 × 10 ⁻⁶ / ° C. Since the thermal expansion coefficient within these ranges is close to the thermal expansion coefficient of the metal, breakage due to thermal shock at the joint between the metal outer packaging material (that is, the positive electrode outer packaging material 13 and / or the negative electrode outer packaging material 17) and the sealing portion 18. Can be effectively suppressed. Glass-based sealing materials that satisfy the various characteristics described above are commercially available. For example, a product group called “POWDER GLASS” (AGC glass frit) and “GLASS PATHE” (AGC glass paste) marketed by AGC Electronics Co., Ltd., and a low melting point glass paste from Central Glass Co., Ltd. To find glass-based sealing materials that satisfy the above-mentioned characteristics in the product group that is commercially available and the product group of vanadium-based low-melting-point glass that is called “Bunny Tect” from Hitachi Chemical Co., Ltd. it can.

Alternatively, the sealing material may be a resin-based sealing material containing a resin. Even in this case, the sealing portion 18 can be formed at a relatively low temperature (for example, 400 ° C. or lower), and as a result, the destruction and alteration of the battery due to the sealing accompanied by heating can be effectively prevented. be able to. The resin preferably has a thermal expansion coefficient of 7 × 10 ⁻⁶ / ° C. or more, more preferably 9 × 10 ^{−6 to} 20 × 10 ⁻⁶ / ° C., and still more preferably 10 × 10 ^{−6 to} 19 × 10 ^{− 6} / ° C., particularly preferably 12 × 10 ⁻⁶ to 18 × 10 ⁻⁶ / ° C., and most preferably 15 × 10 ⁻⁶ to 18 × 10 ⁻⁶ / ° C. The resin is preferably an insulating resin. The insulating resin is preferably a resin (adhesive resin that can be bonded by heat or the like) that can be bonded while maintaining insulation. Examples of preferable insulating resins include olefin resins, acrylic resins, epoxy resins, urethane resins, and silicon resins. A heat-sealing adhesive resin having a low moisture permeability such as a modified polypropylene resin and a modified polyethylene resin is particularly preferable. The insulating resin can be composed of at least one or a plurality of types of laminates. A thermoplastic resin molded sheet may be used as at least one kind of insulating resin. The resin-based sealing material may be made of a mixture of a resin (preferably an insulating resin) and an inorganic material. Preferable examples of such inorganic materials include silica, alumina, zinc oxide, magnesia, calcium carbonate, calcium hydroxide, barium sulfate, mica and talc, and silica is more preferable. For example, a resin-based sealing material made of a mixture of an epoxy resin and silica is preferably exemplified.

Battery thickness The all solid lithium battery preferably has a thickness of 60 to 5000 μm, more preferably 70 to 4000 μm, still more preferably 80 to 3000 μm, particularly preferably 90 to 2000 μm, most preferably 100. ˜1000 μm. According to the present invention, the positive electrode plate can be made relatively thick, while the exterior material also serves as a current collector, so that the thickness of the entire battery can be made relatively thin.

Method for Producing Positive Electrode Active Material Sheet A preferred method for producing the positive electrode active material sheet is described below.

(1) Preparation of raw material particles As raw material particles, particles of a compound such as Li, Co, Ni, Mn, and Al were appropriately mixed so that the composition after synthesis was a positive electrode active material LiMO ₂ having a layered rock salt structure. Things are used. Alternatively, raw material particles having a composition of LiMO ₂ (synthesized particles) can be used.

Or you may use the raw material particle | grains which do not contain a lithium compound as needed. In this case, LiMO ₂ is obtained by further reacting the fired molded body with the lithium compound after the firing process of the molded body. As raw material particles not containing lithium, mixed particles ((Co, Ni, Mn) O _x , (Co, Ni, Al) O _x , (Co, Ni, Mn) of compounds such as Co, Ni, Mn, and Al are used. ) OH _x , (Co, Ni, Al) OH _x, etc.). Preferably, the at least one metal compound is an oxide, hydroxide and / or carbonate of at least one metal selected from the group consisting of Co, Ni, Mn and Al. These particles may be in the form of a mixed powder of two or more kinds of metal compound particles, or may be particles made of a composite compound synthesized by a coprecipitation method.

  A lithium compound may be added in an excess of 0.5 to 30 mol% for the purpose of promoting grain growth or compensating for volatilization during firing. For the purpose of promoting grain growth, 0.001 to 30 wt% of a low melting point oxide such as bismuth oxide or a low melting point glass such as borosilicate glass may be added.

(2) Forming step of raw material particles The raw material particles are formed into a sheet-like self-supporting compact. That is, the “self-supporting molded body” typically can maintain the shape of a sheet-shaped molded body by itself. In addition, even if it alone can not keep the shape of the sheet-like molded body, it may be attached to any substrate or formed into a film and peeled off from this substrate before or after firing, Included in “self-supported compact”.

  As a molding method of the molded body, for example, a doctor blade method using a slurry containing raw material particles can be used. In addition, a drum dryer may be used for forming a formed body, in which a slurry containing a raw material is applied onto a heated drum and the dried material is scraped off with a scraper. In addition, a disk drier can be used for forming the formed body, in which a slurry is applied to a heated disk surface, dried and scraped with a scraper. Moreover, since the hollow granulated body obtained by setting the conditions of a spray dryer suitably can also be regarded as the sheet-like molded object with a curvature, it can be used suitably as a molded object. Furthermore, an extrusion molding method using a clay containing raw material particles can also be used as a molding method of the molded body.

  When using the doctor blade method, the slurry is applied to a flexible plate (for example, an organic polymer plate such as a PET film), and the applied slurry is dried and solidified to form a molded product, and the molded product and the plate are peeled off. By doing so, you may produce the molded object before baking of a plate-like polycrystalline particle. When preparing a slurry or clay before molding, inorganic particles may be dispersed in a suitable dispersion medium, and a binder, a plasticizer, or the like may be added as appropriate. Moreover, it is preferable to prepare the slurry so that the viscosity is 500 to 4000 cP, and it is preferable that the slurry is degassed under reduced pressure.

(3) Baking process of molded body In this baking process, the molded body obtained in the molding process is placed on a setter and fired, for example, in a molded state (a sheet state). Alternatively, the firing step may be one in which a sheet-like formed body is appropriately cut and crushed and placed in a sheath and fired.

  When the raw material particles are mixed particles before synthesis, synthesis, further sintering and grain growth occur in this firing step. In this invention, since a molded object is a sheet form, the grain growth of the thickness direction is restricted. For this reason, after the grains have grown until the number of crystal grains becomes one in the thickness direction of the compact, grain growth proceeds only in the in-plane direction of the compact. At this time, a specific crystal plane which is stable in terms of energy spreads on the sheet surface (plate surface). Therefore, a film-like sheet (self-supporting film) oriented such that a specific crystal plane is parallel to the sheet surface (plate surface) is obtained.

When the raw material particles are LiMO ₂ , the (101) plane and (104) plane, which are crystal planes in which lithium ions can enter and exit satisfactorily, can be oriented so as to be exposed on the sheet surface (plate surface). On the other hand, when the raw material particles do not contain lithium (for example, M ₃ O _{4 having a} spinel structure), the (h00) plane, which becomes the (104) plane when reacted with a lithium compound to form LiMO ₂ , It can be oriented so as to be exposed on the sheet surface (plate surface).

  The firing temperature is preferably 700 ° C to 1350 ° C. When the temperature is lower than 700 ° C., the grain growth is insufficient and the degree of orientation becomes low. On the other hand, decomposition and volatilization proceeds at a temperature higher than 1350 ° C. The firing time is preferably between 1 and 50 hours. If it is shorter than 1 hour, the degree of orientation becomes low. On the other hand, if it is longer than 50 hours, energy consumption becomes too large. The firing atmosphere is appropriately set so that decomposition does not proceed during firing. When the volatilization of lithium proceeds, it is preferable to arrange lithium carbonate or the like in the same sheath to create a lithium atmosphere. When oxygen release or further reduction proceeds during firing, firing is preferably performed in an atmosphere having a high oxygen partial pressure.

  When a sheet oriented by firing is obtained from raw material particles that do not contain a lithium compound, by reacting this with a lithium compound (lithium nitrate, lithium carbonate, etc.), the crystal plane on which the entry and exit of lithium ions is performed is a plate surface Thus, a positive electrode active material film oriented so as to be exposed to the surface is obtained. For example, lithium is introduced by sprinkling the orientation sheet lithium nitrate so that the molar ratio Li / M of Li and M is 1 or more and heat-treating. Here, the heat treatment temperature is preferably 600 ° C to 800 ° C. At a temperature lower than 600 ° C., the reaction does not proceed sufficiently. When the temperature is higher than 900 ° C., the orientation deteriorates.

(Production example of positive electrode active material sheet of preferred composition)
_{Li p (Ni x, Co y} , Al z) O 2 or _{Li p (Ni x, Co y} , Mn z) positive electrode active material sheet using _{O 2} particles, for example, be prepared in the following manner Good. First, a green sheet containing NiO powder, Co ₃ O ₄ powder and AlOOH or Mn ₃ O ₄ powder is formed, and the green sheet is fired at a temperature within a range of 1000 ° C. to 1400 ° C. in an air atmosphere for a predetermined time. By doing so, an independent film-like sheet (self-supporting film) composed of a large number of (h00) -oriented (Ni, Co, Al) O or (Ni, Co, Mn) 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, the “independent” sheet refers to a sheet that can be handled by itself 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). Thus, in the green sheet formed in a self-supporting film shape, the amount of the material existing in the thickness direction is very small compared to the plate surface direction, that is, the in-plane direction (direction orthogonal to the thickness direction). For this reason, 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, even if the thickness of the green sheet is relatively thick, such as about 100 μm or more, the grain growth in the plane direction is more surely promoted by promoting the grain growth as much as possible. 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 or (Ni, Co, Mn) O ceramic sheet obtained by the above process is mixed with lithium nitrate (LiNO ₃ ) and heated for a predetermined time. Thus, lithium is introduced into the (Ni, Co, Al) O or (Ni, Co, Mn) O particles. As a result, the (003) plane is oriented in the direction from the positive electrode plate 12 to the negative electrode layer 16, and the (104) plane is oriented along the plate surface for Li _p (Ni _x , Co _y , Mn _{z) O 2} sheet or _{Li p (Ni x, Co y} , Al z) O 2 sheet is obtained.

Method for Producing Lithium Ion Conductive Material A preferred method for producing an Al-added LLZ ceramic sintered body, which is one of the representative examples of the lithium ion conductive material constituting the solid electrolyte layer 14, will be described below.

  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. Thereafter, in the second firing step, the primary fired powder obtained in the first firing step is fired to synthesize a ceramic having a garnet-type or garnet-like crystal structure containing Li, La, Zr, and oxygen. 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.

(Li component, La component and Zr component)
These various components are not particularly limited, and various metal salts such as metal oxides, metal hydroxides, and metal carbonates containing the respective metal components can be appropriately selected and used. For example, 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. Note that oxygen is usually included as an element constituting a part of a compound containing these constituent metal elements. The raw material for obtaining the ceramic material can contain a Li component, a La component, and a Zr component to such an extent that an LLZ crystal structure can be obtained from each Li component, La component, Zr component, and the like by a solid phase reaction or the like. According to the stoichiometric composition of LLZ, the Li component, La component and Zr component can be used in a composition close to 7: 3: 2 or a composition ratio. When considering the disappearance of the Li component, the Li component includes an amount increased by about 10% from the molar ratio equivalent amount based on the stoichiometry of Li in LLZ, and the La component and the Zr component are each in an LLZ molar ratio. It can contain so that it may become the quantity equivalent to. For example, it can be contained so that the molar ratio of Li: La: Zr is 7.7: 3: 2. When a specific compound is used, the molar ratio is about 3.85: about 3: about 2 when Li ₂ CO ₃ : La (OH) ₃ : ZrO ₂ , and Li ₂ CO ₃ : When La ₂ O ₃ : ZrO ₂ , the molar ratio is about 3.85: about 1.5: about 2, and when LiOH: La (OH) ₃ : ZrO ₂ is about 7.7: about 3: about 2. When LiOH: La ₂ O ₃ : ZrO ₂ , it is about 7.7: about 1.5: about 2. In preparing the raw material powder, a known raw material powder preparation method in the synthesis of ceramic powder can be appropriately employed. For example, the mixture can be mixed uniformly by putting it into a reiki machine or a suitable ball mill.

(First firing step)
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. The first baking step may include a step of heating at a lower heating temperature and a step of heating at a higher heating temperature within the above temperature range. By providing such a heating step, a more uniform ceramic powder can be obtained, and a high-quality sintered body can be obtained by the second firing step. When the first firing step is performed in such a plurality of steps, it is preferable to knead and pulverize using a raikai machine, a ball mill, a vibration mill, or the like after the completion of each firing step. Moreover, it is desirable to carry out the pulverization method by a dry method. By doing so, a more uniform LLZ phase can be obtained by the second firing step. The heat treatment step constituting the first firing step is preferably performed by a heat treatment step of 850 ° C. or more and 950 ° C. or less and a heat treatment step of 1075 ° C. or more and 1150 ° C. or less. More preferably, a heat treatment step of 875 ° C. to 925 ° C. (more preferably about 900 ° C.) and a heat treatment step of 1100 ° C. to 1150 ° C. (more preferably about 1125 ° C.) are used. In the first baking step, the total heating time at the maximum temperature set as the heating temperature as a whole is preferably about 10 hours to 15 hours. In the case where the first baking step is composed of two heat treatment steps, it is preferable that the heating time at the maximum temperature is about 5 to 6 hours. On the other hand, the first firing step can be shortened by changing one or more components of the starting material. For example, when LiOH is used as one of the components contained in the starting material, in order to obtain an LLZ crystal structure, an LLZ component containing Li, La and Zr is heated at a maximum temperature in a heat treatment step of 850 ° C. or more and 950 ° C. or less. The heating time can be 10 hours or less. This is because LiOH used as a starting material forms a liquid phase at a low temperature, and thus easily reacts with other components at a lower temperature.

(Second firing step)
A 2nd baking process can be made into the process of heating the primary baking powder obtained at the 1st baking process at the temperature of 950 degreeC or more and 1250 degrees C or less. According to the second firing step, the primary firing powder obtained in the first firing step is fired, and finally a ceramic having an LLZ crystal structure that is a composite oxide can be obtained. In order to obtain the LLZ crystal structure, for example, an LLZ component including Li, La, and Zr is heat-treated at a temperature of 1125 ° C. or higher and 1250 ° C. or lower. When Li ₂ CO ₃ is used as the Li raw material, it is preferable to perform heat treatment at 1125 ° C. or higher and 1250 ° C. or lower. When the temperature is lower than 1125 ° C., it is difficult to obtain a single phase of LLZ, and the Li conductivity is small. When the temperature exceeds 1250 ° C., the formation of a different phase (La ₂ Zr ₂ O ₇ or the like) is observed, and the Li conductivity is small. Moreover, since crystal growth becomes remarkable, it tends to be difficult to maintain the strength as a solid electrolyte. More preferably, it is about 1180 to 1230 ° C. On the other hand, the temperature of the second firing step can be lowered by changing one or more components of the starting material. For example, when LiOH is used as a Li raw material as a Li raw material, in order to obtain an LLZ crystal structure, an LLZ constituent component including Li, La, and Zr can be heat-treated at a temperature of 950 ° C. or higher and lower than 1125 ° C. This is because LiOH used as a starting material forms a liquid phase at a low temperature, and thus easily reacts with other components at a lower temperature. The heating time at the heating temperature in the second firing step is preferably about 18 hours or more and 50 hours or less. When the time is shorter than 18 hours, the formation of the LLZ ceramics is not sufficient. When the time is longer than 50 hours, it becomes easy to react with the setter via the filling powder, and the crystal growth is not able to maintain the strength as a sample. Because. Preferably it is 30 hours or more. In the second firing step, the primary fired powder is pressure-molded using a well-known pressing technique to give a desired three-dimensional shape (for example, a shape and size that can be used as a solid electrolyte of an all-solid lithium battery). It is preferable to implement the above. By using a molded body, a solid phase reaction is promoted and a sintered body can be obtained. In addition, you may implement separately a sintering process at the temperature similar to the heating temperature in a 2nd baking process by using the ceramic powder obtained by the 2nd baking process as a molded object after a 2nd baking process. When the molded body containing the primary fired powder is fired and sintered in the second firing step, it is preferable to carry out the process so that the molded body is buried in the same powder. By doing so, the loss of Li can be suppressed and the change in composition before and after the second firing step can be suppressed. In addition, the molded body of the raw material powder is usually buried in the raw material powder in a state where the raw material powder is spread and placed. By carrying out like this, reaction with a setter can be suppressed. Moreover, the curvature at the time of baking of a sintered compact can be prevented by pressing a molded object with a setter from the upper and lower sides of a filling powder as needed. On the other hand, when the temperature is lowered by using LiOH as a Li raw material in the second firing step, the primary fired powder compact can be sintered without being embedded in the same powder. This is because the loss of Li is relatively suppressed and the reaction with the setter can be suppressed by lowering the temperature of the second baking step.

  The solid electrolyte layer 14 having the LLZ crystal structure can be obtained by using the powder that has undergone the above-described firing process. The solid electrolyte layer having a crystal structure and containing aluminum is obtained by carrying out either or both of the first firing step and the second firing step in the presence of an aluminum (Al) -containing compound. You may make it manufacture.

  The present invention is more specifically described by the following examples. In addition, the evaluation method of the various parameters regarding the positive electrode plate and the all solid state battery in the following examples was as follows.

<Thickness>
The positive electrode plate was polished with a cross section polisher (CP) so that the cross-section polished surface could be observed, and a cross-sectional image was obtained with a SEM (scanning type microscope) (JSM-6390LA, manufactured by JEOL Ltd.). The thickness of the positive electrode plate was determined based on the obtained cross-sectional image.

（上記式中、Ｉは正極板試料の回折強度であり、Ｉ_０は無配向の参照試料（正極板試料を乳鉢で粉砕して無配向状態にしたもの）の回折強度である。（ＨＫＬ）は配向度を評価したい回折線であり、（００ｌ）以外の回折線に相当にする。（ｈｋｌ）は全ての回折線に相当する。） <Orientation degree>
Using the plate surface of the positive electrode plate as the sample surface and using an XRD apparatus (manufactured by Rigaku Corporation, TTR-III), X-ray diffraction is 2θ in the range of 10 ° to 70 ° at 2 ° / min, step width of 0.02 It was performed under the condition of °. The degree of orientation of the obtained XRD profile was calculated based on the following formula according to the Lotgering method.

(In the above formula, I is the diffraction intensity of the positive electrode plate sample, and I ₀ is the diffraction intensity of a non-oriented reference sample (a non-oriented state obtained by pulverizing the positive electrode plate sample with a mortar) (HKL). Is a diffraction line for which the degree of orientation is to be evaluated, and corresponds to a diffraction line other than (00l) (hkl) corresponds to all diffraction lines.)

<Cycle test>
The manufactured all-solid lithium battery was subjected to a cycle test in order to examine the change in discharge capacity with repeated charge and discharge. This cycle test is the following charge / discharge cycle:
-Charging: Charging to 4.2V at a constant current of 0.1mA, and then charging until the current reaches 0.005mA at a constant voltage, and-Discharging: Discharging at 120 ° C until reaching 2.5V at a constant current of 0.02mA It repeated by calculating by calculating | requiring as a discharge capacity maintenance factor the ratio (%) of the discharge capacity after 100 cycles with respect to the initial discharge capacity. Therefore, the higher the discharge capacity retention rate (%), the better the cycle characteristics.

Examples 1-16, 20 and 25-31
(1) Preparation of positive electrode plate Cobalt hydroxide (Co (OH) ₂ ) powder was prepared. This composite hydroxide powder is an oriented aggregate of plate-like primary particles. This powder was pulverized with a ball mill for a predetermined time (for example, 24 hours) to obtain a raw material powder. The raw material powder and LiOH.H ₂ O powder were weighed and mixed so that the molar ratio of Li / Co was 1.05, and then calcined at 600 ° C. for 3 hours. 100 parts by weight of the obtained powder, 100 parts by weight of a dispersion medium (a mixed solvent containing toluene and isopropanol at a weight ratio of 1: 1), and 10 parts by weight of a binder (polyvinyl butyral, BM-2, manufactured by Sekisui Chemical Co., Ltd.) Parts, 4 parts by weight of a plasticizer (DOP (di (2-ethylhexyl) phthalate), manufactured by Kurokin Kasei Co., Ltd.) and 2 parts by weight of a dispersant (Leodol SP-O30, manufactured by Kao Corporation) were mixed. The mixture was defoamed by stirring under reduced pressure and adjusted to a viscosity of 3000 to 4000 cP. The viscosity was measured with an LVT viscometer manufactured by Brookfield.

  The slurry prepared as described above was formed into a sheet shape on a PET film by a doctor blade method so that the thickness after drying was 60 μm. The obtained sheet was peeled off from the PET film and cut to 2 cm × 2 cm. 400 layers of the cut sheets were laminated and pre-pressed at 120 ° C. with a laminator to obtain a green bulk. The obtained green bulk was heated to 600 ° C. at 20 ° C./h, held for 60 hours, and degreased by lowering the temperature at 20 ° C./h. The obtained degreased bulk was vacuum packed and then pressed with CIP at a predetermined pressing pressure (for example, 3 t). The obtained degreased bulk was heated up to a predetermined firing temperature (for example, 875 ° C.) at 100 ° C./h in an air atmosphere and held for 20 hours. The obtained sintered bulk was cut out by processing so that the cross-sectional direction was the plate surface, and the positive electrode plate was obtained by polishing the surface of the plate surface. The obtained positive electrode plate was bonded to an Al foil as a current collector with a conductive epoxy adhesive containing carbon. The positive electrode plate thus obtained was measured for thickness and degree of orientation by the method described above. The results are shown in Table 1. As shown in Tables 1A and 2A, the positive plates produced in Examples 1 to 16, 20 and 25 to 31 have various thicknesses and orientations, and these are arbitrarily given by appropriately adjusting the production conditions. (For example, the degree of orientation was controlled by appropriately adjusting the raw material grinding time, firing temperature, and molding pressure).

(2) Production of solid electrolyte layer A lithium phosphate sintered compact target having a diameter of 4 inches (about 10 cm) was prepared. Using this target, sputtering was performed using a sputtering apparatus (SPF-430H, manufactured by Canon Anelva) with an RF magnetron method so that the gas type N ₂ was 0.2 Pa, the output was 0.2 kW, and the film thickness was 2 μm. . Thus, a LiPON-based solid electrolyte sputtered film having a thickness of 2 μm was formed on the positive electrode plate.

(3) Production of all-solid lithium battery An Au film having a thickness of 500 mm was formed on the solid electrolyte layer by sputtering using an ion sputtering apparatus (manufactured by JEOL, JFC-1500). On the obtained Au film, a Li metal foil and a Cu foil as a current collecting layer were placed in a glove box in an Ar atmosphere, and pressure-bonded on a hot plate at 200 ° C. Thus, a unit cell (size: 10 mm × 10 mm square) of positive electrode plate / solid electrolyte layer / negative electrode layer was obtained. However, only in Example 6, 50 unit cells were stacked in parallel. The unit battery or laminated battery thus obtained was placed on a stainless steel (SUS) foil (thickness: 20 μm, size: 12 mm × 12 mm square), and the sealing material shown in Table 1 was included around the unit battery or laminated battery. A glass paste was applied at a thickness of 1 mm, covered with a stainless steel (SUS) foil (thickness 20 μm, 12 mm × 12 mm square), and heat-sealed at a predetermined temperature in a vacuum to obtain an all-solid lithium battery.

  In addition, KP312, 9079-150, TNS031W, TNS062-ZB, ASF1290A4, FP-74, BNL115BB, and KP312 shown as sealing materials in Table 1 are all “POWDER GLASS” (AGC) manufactured by AGC Electronics Co., Ltd. Glass frit) is a product name of a product group, and as shown in Tables 1A and 2A, both have a softening temperature of 400 ° C. or less. Since this glass frit is in the form of powder, it was dispersed in a solvent (ethanol) and used as a glass paste when applied around the battery unit.

  The all-solid lithium battery thus produced was subjected to a cycle test according to the above-described procedure in order to examine the change in discharge capacity with repeated charge / discharge. The results were as shown in Tables 1B and 2B.

Example 17
An all-solid lithium battery was prepared and evaluated in the same basic procedure as in Example 4 except that Al was used instead of lithium metal as the negative electrode. The results were as shown in Table 1B.

Example 18
An all-solid lithium battery was prepared and evaluated in the same basic procedure as in Example 4 except that In was used instead of lithium metal as the negative electrode. The results were as shown in Table 1B.

Example 19
As a solid electrolyte layer, instead of a LiPON-based solid electrolyte sputtered film, a Li-La-Zr-O-based solid electrolyte AD film was prepared in the same manner as in Example 4 except that it was prepared as follows. Lithium battery fabrication and various evaluations were performed. The results were as shown in Table 1B.

That is, as a solid electrolyte layer, a Li—La—Zr—O-based solid electrolyte AD film was produced on the positive electrode plate as follows. Lithium hydroxide (Kanto Chemical Co., Inc.), lanthanum hydroxide (Shin-Etsu Chemical Co., Ltd.), zirconium oxide (Tosoh Corp.), and tantalum oxide were prepared as raw material components for preparing the raw material for firing. These powders are weighed and blended so as to be LiOH: La (OH) ₃ : ZrO ₂ : Ta ₂ O ₅ = 7: 3: 1.625: 0.1875, and mixed by a laika machine to be a raw material for firing. Got. As the first firing step, the firing raw material was placed in an alumina crucible, heated at 600 ° C./hour in the air atmosphere, and held at 900 ° C. for 6 hours. As a second firing step, γ-Al ₂ O ₃ is added to the powder obtained in the first firing step so as to have a concentration of 0.6% by mass, and this powder and cobblestone are mixed to form a vibration mill. And pulverized for 3 hours to obtain a powder having a starting material composition of Li _7.0 La _3.0 Zr _1.625 Ta _0.375 O ₁₂ Al _0.1 . The amount of γ-Al ₂ O ₃ added is such that the compositional formula Li _7.0 La _3.0 Zr _1.625 Ta _0.375 assumes that the primary calcined powder has a composition as charged. This corresponds to an amount of 0.1 Al in molar ratio to O ₁₂ . The obtained raw material powder was put in a magnesia sheath and heat-treated at 800 ° C. for 1 hour in an Ar atmosphere to remove CO ₂ and H ₂ O that can be contained in the raw material powder. In the raw material powder thus obtained, although Li and O may deviate from 7 and 12, which are the number of moles of the charged composition, due to defects during firing, etc., the charged composition of Li _7.0 La _3.0 Zr _It has a composition generally based on _1.625 Ta _0.375 O ₁₂ Al _0.1 and does not contain lithium carbonate.

The raw material powder after the heat treatment was crushed in a glove box under an Ar atmosphere using a nylon mesh having an opening diameter of 75 μm, and then deposited by an aerosol deposition (AD) method using N ₂ gas as a carrier gas. . This AD film formation was performed using a film formation apparatus 20 as shown in FIG. A film forming apparatus 20 shown in FIG. 2 is configured as an apparatus used for the AD method in which a raw material powder is injected onto a substrate in an atmosphere at a pressure lower than atmospheric pressure. The film forming apparatus 20 includes an aerosol generating unit 22 that generates an aerosol of a raw material powder containing a raw material component, and a film forming unit 30 that sprays the raw material powder onto a substrate 21 to form a film containing the raw material component. . The aerosol generation unit 22 contains a raw material powder, receives an supply of a carrier gas from a gas cylinder (not shown), generates an aerosol, a raw material supply pipe 24 that supplies the generated aerosol to the film forming unit 30, and An aerosol generation chamber 23 and a vibrator 25 that applies vibration to the aerosol in the aerosol generation chamber 23 at a frequency of 10 to 100 Hz are provided. The film forming unit 30 includes a film forming chamber 32 that injects aerosol onto the substrate 21, a substrate holder 34 that is disposed inside the film forming chamber 32 and fixes the substrate 21, and the substrate holder 34 in the X axis-Y axis direction. And an XY stage 33 that moves. The film forming unit 30 includes a spray nozzle 36 that has a slit 37 formed at the tip thereof and sprays aerosol onto the substrate 21, and a vacuum pump 38 that decompresses the film forming chamber 32. The film forming apparatus 20 may be configured to heat the raw material powder by providing a heating device, a heat-resistant member, or the like in the film forming chamber 32. For example, a heat-resistant member such as quartz glass or ceramics may be used so that heat treatment can be performed at a temperature at which the raw material powder is single-crystallized. The production conditions of the solid electrolyte membrane by the film forming apparatus 20 were as follows. As the substrate, the previously synthesized positive electrode plate was used. Also, oxygen gas having a flow rate of 2 L / min is used as a carrier gas, and the pressure in the film forming chamber is adjusted to 0.1 to 0.2 kPa, and the pressure in the aerosol chamber is adjusted to 50 to 70 kPa to form a film. Went. At that time, the opening size of the nozzle was set to 10 mm × 1.8 mm, and scanning was performed simultaneously with the film formation for 60 reciprocations at a scanning distance of 10 mm and a scanning speed of 5 mm / sec in the short side direction of the nozzle. Thus, a Li-La-Zr-O solid electrolyte AD film having a thickness of 2 m was formed on the positive electrode plate.

Example 21
Instead of using cobalt hydroxide (Co (OH) ₂ ) powder as raw material powder, nickel / cobalt / manganese composite hydroxide having a composition of (Ni _1/3 Co _1/3 Mn _1/3 ) (OH) ₂ An all-solid lithium battery was prepared and evaluated in the same basic procedure as in Example 4 except that powder was used. The cobalt hydroxide powder is an oriented aggregate of plate-like primary particles. The results were as shown in Table 1B.

Example 22
An all-solid lithium battery was prepared and evaluated in the same basic procedure as in Example 4 except that borosilicate glass (manufactured by Schott, product name: Tempax) was used as the sealing material. The results were as shown in Table 2B.

Example 23
An all-solid lithium battery was prepared and evaluated in the same basic procedure as in Example 4 except that a mixture of epoxy resin (manufactured by ThreeBond, product name: 2088E) and SiO ₂ was used as the sealing material. The results were as shown in Table 2B.

Example 24
An all-solid lithium battery was prepared and evaluated in the same basic procedure as in Example 4 except that maleic acid-modified polypropylene (manufactured by Okura Kogyo Co., Ltd., product name: tab tape) was used as the sealing material. The results were as shown in Table 2B.

DESCRIPTION OF SYMBOLS 10 All-solid-state lithium battery 12 Positive electrode plate 13 Positive electrode exterior material 14 Solid electrolyte layer 16 Negative electrode layer 17 Negative electrode exterior material 18 Sealing part

Claims (20)

A positive electrode plate formed of an oriented polycrystal formed by aligning a plurality of lithium transition metal oxide particles;
A solid electrolyte layer provided on the positive electrode plate and made of a lithium ion conductive material;
A negative electrode layer provided on the solid electrolyte layer;
A metal positive electrode exterior material that covers the outside of the positive electrode plate and also functions as a positive electrode current collector;
A metal negative electrode exterior material that covers the outside of the negative electrode layer and also functions as a negative electrode current collector;
A sealing portion made of a sealing material that seals the exposed portion of the positive electrode plate, the solid electrolyte layer, and the negative electrode layer, which is not covered with the positive electrode exterior material and the negative electrode exterior material;
An all-solid-state lithium battery comprising:
The thickness of the positive electrode plate is 15 to 60 μm, and the ratio of the thickness t _P of the positive electrode plate to the thickness t _N of the negative electrode layer is 1 ≦ t _P / t _N ≦ 15,
An all-solid lithium battery in which the oriented polycrystal has an orientation degree of 10% or more.   The all-solid-state lithium battery of Claim 1 whose said sealing material is a resin-type sealing material containing resin.   The all-solid-state lithium battery according to claim 2, wherein the resin-based sealing material is made of a mixture of the resin and an inorganic material.   The all-solid-state lithium battery of Claim 3 whose said inorganic material is a silica.   The all-solid-state lithium battery as described in any one of Claims 1-4 whose said sealing material is a glass-type sealing material which comprises glass.   The all-solid-state lithium battery of Claim 5 in which the said glass-type sealing material contains at least 1 sort (s) selected from the group which consists of V, Sn, Te, P, Bi, B, Zn, and Pb. The all-solid-state lithium battery of Claim 5 or 6 in which the said glass-type sealing material has a thermal expansion coefficient of ^7x10 < ^-6 > / degreeC or more.   The all-solid-state lithium battery as described in any one of Claims 5-7 in which the said glass-type sealing material has a softening temperature of 400 degrees C or less. The all-solid lithium battery according to claim 1, wherein the sealing material has a resistivity of 1 × 10 ⁶ Ωcm or more.   The all-solid-state lithium battery according to any one of claims 1 to 9, wherein the oriented polycrystal has an orientation degree of 15 to 95%.   The all-solid lithium battery according to claim 1, wherein the all-solid lithium battery has a thickness of 60 to 5000 μm.   The plurality of lithium transition metal oxide particles are oriented in a direction such that a specific crystal plane of the particles intersects the plate surface of the positive electrode plate. All solid lithium battery.   The all-solid-state lithium battery according to claim 12, wherein the lithium transition metal oxide particles have a layered rock salt structure, and the specific crystal plane is a (003) plane. The lithium transition metal oxide particles are Li _x M1O ₂ or Li _x (M1, M2) O ₂ (wherein 0.5 <x <1.10, M1 is selected from the group consisting of Ni, Mn and Co) At least one transition metal element, M2 is Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, Ag, Sn, Sb, The all-solid-state lithium battery as described in any one of Claims 1-13 which has a composition represented by this at least 1 type of element selected from the group which consists of Te, Ba, and Bi. The total composition according to claim 14, wherein the composition is represented by Li _x (M1, M2) O ₂ , M1 is Ni and Co, and M2 is at least one selected from the group consisting of Mg, Al, and Zr. Solid lithium battery. The all-solid-state lithium battery according to claim 14, wherein the composition is represented by Li _x M1O ₂ and M1 is Ni, Mn and Co, or M1 is Co.   The lithium ion conductive material constituting the solid electrolyte layer is composed of a garnet ceramic material, a nitride ceramic material, a perovskite ceramic material, a phosphate ceramic material, a sulfide ceramic material, or a polymer material. The all-solid-state lithium battery as described in any one of Claims 1-15.   The lithium ion conductive material constituting the solid electrolyte layer is composed of a Li-La-Zr-O based ceramic material and / or a lithium phosphate oxynitride (LiPON) based ceramic material. The all-solid-state lithium battery as described in any one.   The all-solid-state lithium battery as described in any one of Claims 1-18 whose said positive electrode exterior material and the said negative electrode exterior material are metal foil. The all-solid lithium battery according to claim 19, wherein the metal foil has a thickness of 1 to 30 μm.

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