JP2016072241A - Lithium cobaltate orientated sintered plate and manufacturing method thereof, and method for forming solid electrolyte layer on lithium cobaltate orientated sintered plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium cobaltate orientated sintered plate which is hard to cause a trouble in a battery performance even if a LiPON based solid electrolyte layer is formed on its surface by sputtering.SOLUTION: A method for manufacturing a lithium cobaltate orientated sintered plate comprises (a)a step for preparing a green sheet including CoOparticles; (b)a step for sintering the green sheet into a CoOoriented sintered plate; and (c)a step for sintering the CoOoriented sintered plate in coexistence of a lithium source to introduce lithium thereinto, thereby forming the lithium cobaltate orientated sintered plate primarily including LiCoO. The method further comprises: (d1)a step for covering a surface of the CoOoriented sintered plate with a liquid solution or slurry of a compound including at least one additive element of Ti, Al and/or Zr prior to the step (c); or (d2)a step for coating the surface of the lithium cobaltate oriented sintered material with the liquid solution or slurry and then, sintering the lithium cobaltate oriented sintered material coated with the liquid solution or slurry after the step (c).SELECTED DRAWING: None

Description

  The present invention relates to a lithium cobaltate oriented sintered plate, a method for producing the same, and a method for forming a solid electrolyte layer on the lithium cobaltate oriented sintered plate.

As a positive electrode active material in a lithium secondary battery (sometimes called a lithium ion secondary battery), a material using a lithium composite oxide (lithium transition metal oxide) having a layered rock salt structure is widely known. . In this type of positive electrode active material, the diffusion of lithium ions (Li ⁺ ) therein is performed in the in-plane direction of the (003) plane (that is, any direction in a plane parallel to the (003) plane). It is known that lithium ions enter and exit from crystal planes other than the (003) plane (for example, the (101) plane or the (104) plane).

Therefore, in this type of positive electrode active material, a surface that comes into contact with the electrolyte more in a crystal plane (a plane other than the (003) plane, for example, the (101) plane or the (104) plane) on which lithium ions can enter and exit satisfactorily. Attempts have been made to improve the battery characteristics of lithium secondary batteries by exposing them to the above. For example, Patent Document 1 (WO 2010/074304), a sheet containing _Co 3 _{O 4} particles by firing a green sheet (h00) face is oriented parallel to the sheet surface including _Co 3 _{O 4} It is disclosed that a LiCoO ₂ ceramic sheet (positive electrode active material film) having a (104) plane oriented parallel to the sheet surface is produced by forming and then introducing Li. This document also describes that Bi ₂ O ₃ is further added as a grain growth promoting material to a green sheet containing Co ₃ O ₄ .

  By the way, 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, in Patent Document 2 (Japanese Patent Laid-Open No. 2007-103129), a positive electrode current collector layer, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer, and a negative electrode current collector layer are arranged in this order on a substrate. A thin film solid secondary battery formed by a sputtering method is disclosed, and it is also described that lithium phosphate oxynitride (LiPON) can be used as a solid electrolyte.

International Publication No. 2010/0704304 JP 2007-103129 A

As the positive electrode active material plate, a LiCoO ₂ oriented sintered plate in which at least one of the (104) plane and the (101) plane is oriented parallel to the plate surface is used, and a LiPON film is formed thereon as a solid electrolyte layer. Thus, a high-capacity all-solid lithium battery can be produced. This is because the positive electrode active material layer can be made thicker than a conventional thin-film all-solid battery using a non-oriented positive electrode active material layer due to the orientation of the LiCoO ₂ oriented sintered plate. . That is, in such a LiCoO ₂ oriented sintered plate, since the (104) surface and (101) surface where lithium ions can enter and exit well are oriented parallel to the plate surface, a thick positive electrode active material is provided. However, it is easy to remove and insert high-efficiency lithium ions over the entire thickness of the positive electrode active material layer, and the capacity improvement effect brought about by the thick positive electrode active material can be maximized.

However, when a solid electrolyte layer made of LiPON is formed on the surface of such a LiCoO ₂ oriented sintered plate by sputtering, it is hardly seen when a film is formed on a conventional thin film positive electrode active material layer, In many cases, the surface morphology becomes grainy, and granular precipitates made of lithium compounds are often generated on the surface of the LiPON layer. In fact, if an LiPON layer is formed by sputtering to a thickness of 2 μm or less that can ensure practical battery performance to produce an all-solid-state battery, the probability of causing a short circuit (short circuit) increases and the product yield decreases. This is considered to be caused by the above-described grainy surface morphology and precipitates on the surface of the LiPON layer.

In general, the present inventors have coated a LiCoO ₂ oriented sintered plate or its precursor Co ₃ O ₄ oriented sintered plate with a solution or slurry of a compound containing a predetermined additive element such as Ti, fired, etc. As a result, it was found that a LiCoO ₂ oriented sintered plate that is unlikely to cause defects in battery performance can be provided even when a solid electrolyte layer made of LiPON is formed on the surface by sputtering to form a battery.

  Accordingly, an object of the present invention is to provide a lithium cobalt oxide oriented sintered plate which is less likely to cause a problem in battery performance even when a solid electrolyte layer made of LiPON is formed on the surface by sputtering to form a battery. .

According to one aspect of the present invention, there is provided a method for producing a lithium cobaltate oriented sintered plate used as a positive electrode active material for an all-solid-state lithium battery, wherein the lithium cobaltate sintered plate comprises (104) face of LiCoO ₂ and (101) At least one of the surfaces is oriented parallel to the plate surface,
(A) preparing a green sheet having a thickness of 100 μm or less, comprising Co ₃ O ₄ particles;
(B) firing the green sheet at 900 to 1400 ° C. to obtain a Co ₃ O ₄ oriented sintered plate having the (h00) plane oriented parallel to the sheet surface;
(C) firing the Co ₃ O ₄ oriented sintered plate in the presence of a lithium source to introduce lithium, thereby forming a lithium cobaltate oriented sintered plate mainly composed of LiCoO ₂ ;
And a solution or slurry of a compound containing at least one additional element selected from the group consisting of Ti, Al and Zr on the surface of the Co ₃ O ₄ oriented sintered plate prior to the step (c) A solution of a compound containing at least one additional element selected from the group consisting of Ti, Al, and Zr on the surface of the lithium cobalt oxide oriented sintered body after the step (d1) of coating with the step (d1) or the step (c) Alternatively, a method is provided, further comprising the step (d2) of coating the lithium cobalt oxide oriented sintered body coated with a slurry and coated with the solution or the slurry.

According to another aspect of the present invention, a lithium cobaltate oriented sintered plate used as a positive electrode active material of an all-solid lithium battery, wherein the lithium cobaltate oriented sintered plate is mainly composed of LiCoO ₂ , and At least one of (104) plane and (101) plane of LiCoO ₂ is oriented parallel to the plate surface,
Provided is a lithium cobaltate oriented sintered plate in which the surface of the lithium cobaltate oriented sintered plate is coated with an oxide containing at least one additional element selected from the group consisting of Ti, Al, and Zr. Is done.

According to still another aspect of the present invention, there is provided a method for forming a solid electrolyte layer on a lithium cobaltate oriented sintered plate for the production of an all-solid lithium battery,
Preparing a lithium cobaltate oriented sintered plate according to the method according to the above aspect, or preparing a lithium cobaltate oriented sintered plate according to the above aspect;
Forming a solid electrolyte layer made of a lithium phosphate oxynitride (LiPON) ceramic material on the surface of the lithium cobaltate oriented sintered plate by sputtering;
A method is provided comprising:

Lithium cobaltate oriented sintered plate and a manufacturing method thereof The present invention relates to a method for producing a positive active material of lithium cobaltate oriented sintered plate used as the all-solid lithium battery. The oriented sintered plate produced according to the present invention is mainly composed of LiCoO ₂ . LiCoO ₂ has a layered rock salt structure, but the lithium cobaltate oriented sintered plate of the present invention has at least one of the (104) plane and (101) plane of LiCoO ₂ oriented parallel to the plate plane. It will be. However, when the thickness of the lithium cobaltate oriented sintered plate is thin, the orientation of the (104) plane becomes dominant, whereas when the thickness of the lithium cobaltate oriented sintered plate is thick, the orientation of the (101) plane becomes dominant. There is a tendency. Further, due to the manufacturing method described later, the surface of the lithium cobalt oxide oriented sintered plate can be coated with an oxide containing at least one additional element selected from the group consisting of Ti, Al, and Zr. However, the lithium cobalt oxide oriented sintered plate is Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, and the like within the scope of the present invention. One or more elements such as Zr, Nb, Mo, Ag, Sn, Sb, Te, Ba, Bi, etc. are further added in a doping or equivalent form (for example, partial solid solution or segregation in the surface layer of crystal grains). May be.

The method for producing a lithium cobaltate oriented sintered plate according to the present invention comprises (a) preparing a green sheet containing Co ₃ O ₄ particles, and (b) firing the green sheet to obtain Co ₃ O ₄ oriented sintered. And (c) introducing lithium into the Co ₃ O ₄ oriented sintered plate to form a lithium cobaltate oriented sintered plate. Prior to the step (c), the surface of the Co ₃ O ₄ oriented sintered plate is a compound containing at least one additional element selected from the group consisting of Ti, Al and Zr (hereinafter also referred to as an additive element compound). The surface of the lithium cobalt oxide oriented sintered body is coated with the solution or slurry of the additive element compound after the step (d1) or (c) step, and the cobalt coated with the solution or slurry A step (d2) of firing the lithium acid lithium oriented sintered body is performed. Thus, a LiCoO ₂ oriented sintered plate or a Co ₃ O ₄ oriented sintered plate that is a precursor thereof (hereinafter, both may be collectively referred to as an “oriented positive electrode plate”) may be used as a predetermined additive element such as Ti. LiCoO ₂ orientation that hardly causes defects in battery performance even when a solid electrolyte layer made of LiPON is formed on the surface by sputtering and coated with a solution or slurry of a compound containing hydrogen A sintered plate can be provided. That is, as described above, when a thin solid electrolyte layer made of LiPON is formed by sputtering on the surface of the LiCoO ₂ oriented sintered plate that has not been subjected to the above-described coating treatment, the surface morphology has a granular feeling, and the LiPON layer In many cases, granular precipitates made of a lithium compound are generated on the surface of the metal, and when the battery is formed, the product yield tends to decrease due to short-circuiting or the like. However, according to the present invention, a LiPON system in which an oriented sintered plate is coated with a solution or slurry of a compound containing an additive element such as Ti and fired to form a film on the surface of the LiCoO ₂ oriented sintered plate by sputtering. The surface morphology of the solid electrolyte layer is improved, and further generation of precipitates on the surface of the LiPON layer is not observed. As a result, the probability of causing a short circuit when battery-powered is significantly reduced (that is, the yield is improved). The reason for this improvement is not clear, but the surface of the lithium cobalt oxide oriented sintered plate can be coated with an oxide containing an additive element of Ti, Al and / or Zr. It is presumed that abnormal discharge during sputtering is less likely to occur due to changes or the like, or that the diffusion of elements between the LiCoO ₂ oriented sintered plate and the LiPON layer is suppressed during sputtering due to the coating layer. .

  Hereinafter, the detail of each process of the manufacturing method of this invention is demonstrated.

(A) Preparation of Green Sheet In this step (a), a green sheet having a thickness of 100 μm or less and containing Co ₃ O ₄ particles is prepared. The green sheet preferably further contains bismuth oxide (typically Bi ₂ O ₃ particles) as a grain growth promoter. The green sheets, Co ₃ O ₄ particles and bismuth oxide optionally a raw material containing (typically Bi ₂ O ₃ particles) may be made by molding into a sheet. The amount of Bi ₂ O ₃ particles added is not particularly limited, but is preferably 0.1 to 30% by weight, more preferably 1 to 30% by weight based on the total amount of Co ₃ O ₄ particles and Bi ₂ O ₃ particles. 20% by weight, more preferably 3 to 10% by weight. The volume-based D50 particle size of _Co 3 _{O 4} particles is preferably from 0.1 to 2.0 [mu] m, more preferably 0.3～1.2Myuemu. The volume-based D50 particle size of Bi ₂ O ₃ particles is preferably 0.1 to 1.0 μm, more preferably 0.2 to 0.5 μm. The thickness of the green sheet is 100 μm or less, preferably 1 to 60 μm, and more preferably 5 to 40 μm. The green sheet may include CoO particles and / or Co (OH) ₂ particles in place of all or part of the Co ₃ O ₄ particles. In this case, the step (b) by subjecting the firing), can be a (h00) plane oriented parallel to the sheet surface was CoO-based sintered intermediates or _Co 3 _{O 4} oriented sintered plate, as a result, a _Co 3 _{O 4} particles The lithium cobalt oxide oriented sintered plate can be produced in the same manner as in the case of using the green sheet.

  Examples of a method for forming a green sheet include (i) a doctor blade method using a slurry containing raw material particles, and (ii) applying a slurry containing the raw material onto a heated drum and drying it with a scraper. A method using a drum dryer, (iii) applying a slurry to a heated disk surface, drying it and scraping it off with a scraper, (iv) setting the conditions of a spray dryer as appropriate Thus, a method of obtaining a hollow granulated body as a sheet-like molded body having a curvature, (v) an extrusion molding method using a clay containing raw material particles, and the like can be mentioned. A particularly preferable sheet forming method is a doctor blade method. 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 body, and the molded body and the board are peeled off. Thus, a green sheet may be produced. When preparing a slurry or clay before molding, inorganic particles may be dispersed in a 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 to defoam under reduced pressure. The shape of the green sheet may be circular from the viewpoint of preventing wrinkles due to firing shrinkage.

In (b) _Co 3 _{O 4} oriented sintered plate prepared in this step (b), and firing the green sheet at 900~1400 ℃, (h00) face _Co 3 _{O 4} orientation is oriented parallel to the seat surface A sintered plate is obtained. That is, the Co ₃ O ₄ particles before firing have an isotropic form, and therefore the green sheet does not initially have orientation, but the Co ₃ O ₄ particles undergo phase transformation to CoO upon firing, and grain growth occurs. In this step, orientation occurs (hereinafter referred to as CoO oriented grain growth). At that time, the Co ₃ O ₄ particles temporarily pass through a sintered intermediate in which the (h00) plane (h is an arbitrary integer, for example, h = 2) is changed to CoO oriented parallel to the sheet surface. Become. That is, at 900 ° C. or higher (eg, 920 ° C. or higher), the Co oxide undergoes a phase transformation from a spinel structure represented by Co ₃ O ₄ at room temperature to a CoO rock salt structure. By this firing, Co ₃ O ₄ is reduced and transformed into CoO, and the sheet is densified. Then, CoO is oxidized to Co ₃ O ₄ in the process of lowering the temperature of the fired intermediate after firing. At that time, the orientation orientation of CoO is inherited by Co ₃ O ₄ , thereby forming an oriented sintered plate composed of a large number of Co ₃ O ₄ particles oriented so that the (h00) plane is parallel to the sheet surface. The In particular, in the presence of bismuth oxide (typically Bi ₂ O ₃ ), oriented grain growth of CoO is promoted. However, when the green sheet contains bismuth oxide, bismuth volatilizes and is removed from the sheet during firing. The firing temperature of the green sheet is 900 to 1400 ° C. (eg 900 to 1350 ° C.), preferably 1000 to 1350 ° C. (eg 1000 to 1300 ° C.), more preferably 1100 to 1300 ° C. The green sheet is preferably fired at the firing temperature for 1 to 20 hours, more preferably 2 to 10 hours. For example, the temperature lowering rate after firing is preferably 10 to 200 ° C./h, more preferably 20 to 100 ° C./h.

The green sheet thickness of 100 μm or less contributes to the CoO grain growth. That is, in a green sheet having a thickness of 100 μm or less, the amount of material present in the thickness direction is extremely small compared to the in-plane direction (the direction perpendicular 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 a two-dimensional direction in the sheet surface (hereinafter referred to as a plane direction). This reliably promotes grain growth in the surface direction. In particular, even when the green sheet is formed as thin as possible (for example, several μm or less) or the green sheet is relatively thick (up to about 100 μm, for example, about 20 μm), the grain growth is promoted as much as possible. By doing so, grain growth in the surface direction can be surely promoted. In any case, at the time of firing, only the particles having the crystal plane with the lowest surface energy in the plane of the green sheet are selectively grown in a flat shape (plate shape) in the plane direction. As a result, by firing the green sheet, CoO plate-like crystal grains having a large aspect ratio and oriented so that the (h00) plane is parallel to the plate surface of the grains are oriented with the (h00) plane parallel to the sheet plane. A calcined intermediate containing is obtained. Thereafter, CoO is oxidized to Co ₃ O ₄ in the process of lowering the temperature of the sintered intermediate, and an oriented sintered plate comprising a large number of Co ₃ O ₄ particles oriented so that the (h00) plane is parallel to the sheet surface Is formed as described above.

By the way, the oriented sintered plate comprising a large number of Co ₃ O ₄ particles is an independent plate-like sheet. An “independent” sheet refers to a sheet that can be handled as a single unit independently of other supports 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 this way, a self-supporting oriented sintered plate is obtained in which a large number of grains oriented such that the (h00) plane is parallel to the grain plane. This self-supporting plate can be a dense ceramic sheet in which a large number of particles as described above are bonded without gaps.

(C) Introduction of lithium In this step (c), a Co ₃ O ₄ oriented sintered plate is baked in the presence of a lithium source to introduce lithium, and thereby a lithium cobaltate oriented sintered plate mainly composed of LiCoO _2. Form. The introduction of lithium is preferably performed by reacting a Co ₃ O ₄ oriented sintered plate with a lithium compound. Examples of lithium compounds for introducing lithium include (i) lithium hydroxide, (ii) various lithium salts such as lithium carbonate, lithium nitrate, lithium acetate, lithium chloride, lithium oxalate, and lithium citrate, (iii) Examples include lithium alkoxides such as lithium methoxide and lithium ethoxide, and lithium hydroxide, lithium carbonate, or a mixture thereof is particularly preferable. Conditions for introducing lithium, for example, the mixing ratio, heating temperature, heating time, atmosphere, and the like may be appropriately set in consideration of the melting point, decomposition temperature, reactivity, etc. of the material used as the lithium source, and are not particularly limited. For example, lithium can be introduced into the Co ₃ O ₄ particles by applying a predetermined amount of a slurry in which LiOH powder is dispersed on a Co ₃ O ₄ oriented sintered plate and drying it, followed by heating. The heating temperature at this time is preferably 600 to 950 ° C. (for example, 600 to 880 ° C.), and it is preferable to perform heating at a temperature within this range for 2 to 20 hours. As another method, a predetermined amount of lithium carbonate is placed on a (h00) -oriented Co ₃ O ₄ oriented sintered plate and heated to introduce lithium into the Co ₃ O ₄ particles. Lithium carbonate may be placed by placing it on a molded body sheet in the form of a lithium-containing sheet containing lithium carbonate, but the Co ₃ O ₄ oriented sintered plate is placed from above and below the lithium-containing sheet. You may carry out by pinching with. The amount of the lithium compound attached to the Co ₃ O ₄ oriented sintered plate is preferably 1.0 or more in terms of Li / Co ratio, more preferably 1.0 to 4.0, and even more preferably 1.2. ~ 3.0. Even when there is too much Li, there is no problem since the excess Li volatilizes and disappears with heating. In order to improve the flatness of the lithium cobalt oxide oriented sintered plate (for example, to suppress the degree of unevenness of the plate surface to be small), the Co ₃ O ₄ oriented fired plate may be heated in a state where a load is applied. In order to sufficiently supply oxygen necessary for synthesis to the plate surface of the Co ₃ O ₄ oriented fired plate, it may be weighted with a porous setter or a setter having a hole (for example, a honeycomb setter). When the lithium cobaltate oriented sintered plate is relatively thick (for example, 30 μm or more in thickness), the Li raw material to be deposited becomes bulky, and a part of the Li raw material melted during heating flows out without being used for synthesis, Prone to poor synthesis. In such a case, the step of attaching and heating the Li raw material (that is, the step of introducing Li) may be repeated.

The lithium cobalt oxide oriented sintered plate thus obtained is obtained by aligning at least one of the (104) plane and the (101) plane of LiCoO ₂ in parallel with the plate plane. Therefore, the (104) plane and the (101) plane where lithium ions enter and exit well are aligned so as to be parallel to the plate surface of the oriented sintered plate. For this reason, when this oriented sintered plate is used as a positive electrode active material to form a battery, exposure (contact) of the surface to the electrolyte is increased, and the (003) surface (lithium) on the surface of the particle or plate is increased. The exposure ratio of the surface that is not suitable for ion entry / exit is extremely low. Therefore, for example, when a lithium cobaltate oriented sintered plate is used as a positive electrode material for a solid lithium secondary battery, high capacity and high rate characteristics can be achieved simultaneously. The thickness of the lithium cobalt oxide oriented sintered plate is preferably 5 to 75 μm, more preferably 10 to 60 μm, still more preferably 20 to 50 μm, and particularly preferably 20 to 40 μm. The size of the lithium cobalt oxide oriented sintered plate is preferably 5 mm × 5 mm square or more, more preferably 10 mm × 10 mm to 100 mm × 100 mm square, and further preferably 10 mm × 10 mm to 50 mm × 50 mm square. Is preferably 25 mm ² or more, more preferably 100 to 10000 mm ² , and still more preferably 100 to 2500 mm ² .

(D) Coating treatment with additive element This step (d) (that is, steps (d1) and (d2)) is the addition of at least one selected from the group consisting of Ti, Al, and Zr to the oriented sintered plate. It is a step of attaching a compound containing an element (hereinafter referred to as an additive element compound) and firing as necessary, and may be a step (d1) performed prior to the step (c), or may be performed after the step (c). Step (d2) may be used. Specifically, when the additive element compound is attached prior to step (c), the subsequent firing can be performed by firing in step (c). On the other hand, when the additive element compound is deposited after the step (c), firing is separately performed thereafter. That is, in the step (d), the step of coating the surface of the Co ₃ O ₄ oriented sintered plate with the solution or slurry of the additive element compound prior to the step (c) (d1), or the lithium cobaltate orientation after the step (c) The surface of the sintered body may be coated with a solution or slurry of the additive element compound, and any one of the steps (d2) of firing the lithium cobaltate oriented sintered body coated with the solution or slurry.

  According to a preferred embodiment of the present invention, the additive element compound may be a Ti-containing compound. Preferred forms of Ti-containing compounds include nitrates, sulfates, acetates, carbonates, chlorides, oxides, alkoxides, and any combinations thereof. According to another preferred embodiment of the present invention, the additive element compound may be an Al-containing compound. Preferred forms of Al-containing compounds include nitrates, sulfates, acetates, carbonates, chlorides, oxides, alkoxides, and any combination thereof. According to still another preferred embodiment of the present invention, the additive element compound may be a Zr-containing compound. Preferred forms of Zr-containing compounds include nitrates, sulfates, acetates, carbonates, chlorides, oxides, alkoxides, and any combination thereof. In any embodiment, the compound is a compound that, after firing, provides an oxide containing at least one additive element selected from the group consisting of Ti, Al, and Zr on the surface of the lithium cobalt oxide oriented sintered plate. desirable. Needless to say, any combination of two or more of Ti-containing compounds, Al-containing compounds, and Zr-containing compounds may be used.

  The additive element compound is provided in the form of a solution or slurry containing the additive element compound. Therefore, the adhesion of the additive element compound to the oriented sintered plate is caused by immersing the oriented sintered body in the solution or slurry containing the additive element compound and subsequent drying, or such solution or slurry on the oriented sintered body. What is necessary is just to perform by application | coating and subsequent drying. In this case, the concentration of the aqueous solution containing the additive element compound is not particularly limited, but is preferably 0.01 to 2 mol / L, more preferably 0.05 to 1 mol / L.

  The firing in the step (d2) is preferably performed at a firing temperature of 300 to 900 ° C, preferably 350 to 750 ° C, more preferably 350 to 600 ° C, and further preferably 400 to 550 ° C. This firing is preferably performed at the firing temperature for 0.5 to 10 hours, and more preferably for 1 to 5 hours. The firing atmosphere is not particularly limited, but may be performed in an oxidizing atmosphere such as an air atmosphere. The additive element compound may be attached to the oriented sintered plate by a vapor phase method such as sputtering.

  As described above, the lithium cobalt oxide oriented sintered plate is made of Mg, Al, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, and Sr without departing from the spirit of the present invention. , Y, Zr, Nb, Mo, Ag, Sn, Sb, Te, Ba, Bi, and the like may be contained in one or more elements, and such elements are added in the steps (a) to (d) described above. ) (Typically in step (a) or step (c)).

Forming Method of Solid Electrolyte Layer on Lithium Cobalt Oxide Oriented Sintered Plate The lithium cobaltate oriented sintered plate of the present invention is a battery even when it is formed into a battery by forming a solid electrolyte layer made of LiPON on the surface by sputtering. Less prone to performance problems. For this reason, the lithium cobaltate oriented sintered plate of the present invention is preferably used for the production of an all-solid lithium battery. In this case, the formation of the solid electrolyte layer on the lithium cobaltate oriented sintered plate is performed by lithium cobaltate. It is preferable to carry out by forming a solid electrolyte layer made of a lithium phosphate oxynitride (LiPON) ceramic material on the surface of the oriented sintered plate by sputtering. 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). Therefore, the formation of the LiPON-based solid electrolyte layer by sputtering is performed by using a lithium phosphate sintered compact target as a Li source, a P source, and an O source, and introducing N ₂ as a gas species as an N source. Follow the instructions below. The sputtering method is not particularly limited, but the RF magnetron method is preferable. In addition, in order to improve the surface smoothness of the oriented sintered plate, the surface may be lightly polished with polishing paper or a router. In the polished portion, the additive element compound after firing (preferably, an oxide containing at least one additive element selected from the group consisting of Ti, Al, and Zr) is removed, but the smooth surface Therefore, while the solid electrolyte is satisfactorily formed, the solid electrolyte is satisfactorily formed at the unpolished portion (recessed portion) by the effect of the additive element compound after firing. This increases the surface smoothness of the solid electrolyte and facilitates the formation of the negative electrode.

  The thickness of the solid electrolyte layer is preferably 0.1 to 10 μm, more preferably 0.2 to 5 μm, still more preferably 0.5 to 4 μm, particularly preferably 1 to 3 μm, and most preferably 1 to 2 μm. is there. The lithium cobalt oxide oriented sintered plate according to the present invention exhibits a good surface morphology even when such a thin LiPON-based solid electrolyte layer is formed thereon by sputtering, thereby incorporating it into an all-solid lithium battery. In this case, it is possible to realize a high yield by significantly reducing battery performance defects (such as short circuit).

  The present invention is more specifically described by the following examples.

Example 1 (Comparison)
(1) Preparation Comparative Example of LiCoO ₂ oriented sintered plate, by the following procedure, without performing the coating process in the added element (step (d1) and (d2)), to prepare a LiCoO ₂ oriented sintered plate .

(1a) Preparation of Green Sheet Co ₃ O ₄ raw material powder (volume basis D50 particle size 0.3 μm, manufactured by Shodo Chemical Co., Ltd.) at a rate of 10 wt% Bi ₂ O ₃ (volume basis D50 particle size 0.3 μm) , Manufactured by Taiyo Mining Co., Ltd.) to obtain a mixed powder. 100 parts by weight of the mixed powder, 100 parts by weight of a dispersion medium (toluene: isopropanol = 1: 1), 10 parts by weight of a binder (polyvinyl butyral: product number BM-2, manufactured by Sekisui Chemical Co., Ltd.), and a plasticizer (DOP) : 4 parts by weight of Di (2-ethylhexyl) phthalate (manufactured by Kurokin Kasei Co., Ltd.) and 2 parts by weight of a dispersant (product name: Leodol SP-O30, manufactured by Kao Corporation) were mixed. The mixture was defoamed by stirring under reduced pressure and adjusted to a viscosity of 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 so as to have a thickness after drying of 24 μm by a doctor blade method to obtain a green sheet.

(1b) Production of Oriented Sintered Plate A green sheet peeled off from a PET film was cut into a 50 mm square with a cutter, and a zirconia setter (size 90 mm square, height 1 mm) embossed with a projection size of 300 μm After placing at the center and firing at 1300 ° C. for 5 hours, the temperature was decreased at a temperature decrease rate of 50 ° C./h, and the portion not welded to the setter was taken out as a Co ₃ O ₄ oriented sintered plate.

(1c) Introduction of Lithium LiOH · H ₂ O powder (manufactured by Wako Pure Chemical Industries, Ltd.) was pulverized to 1 μm or less with a jet mill to prepare a slurry dispersed in ethanol. This slurry was applied to a Co ₃ O ₄ oriented sintered plate so that Li / Co = 1.3, and dried. Then, to obtain a LiCoO ₂ oriented sintered plate by 10 hours of heat treatment at 840 ° C. in air.

(2) Various evaluations The following evaluation was performed on the LiCoO ₂ oriented sintered plate thus prepared.

(2a) Confirmation of orientation by XRD measurement In order to confirm that the (104) plane of the LiCoO ₂ oriented sintered plate is oriented parallel to the plate surface, XRD (X-ray diffraction) measurement was performed. Specifically, using an XRD apparatus (manufactured by Rigaku Corporation, Geiger Flex RAD-IB), an XRD profile was measured when the surface of the sintered plate was irradiated with X-rays. From this XRD profile, the ratio I _[003] / I _[104] of the diffraction intensity (peak height) by the (003) plane to the diffraction intensity (peak height) by the (104) plane was found to be 0.3. It was. On the other hand, when the same plate was sufficiently pulverized in a mortar to form a powder, and the profile of the powder XRD was measured, I _[003] / I _[104] was 1.6. From this, it was confirmed that many (104) planes exist in parallel to the plate surface, that is, they are oriented.

(2b) Production and Evaluation of Battery (i) Production of Positive Electrode A LiCoO ₂ oriented sintered plate was fixed to a stainless steel current collector plate with an epoxy-based conductive adhesive in which conductive carbon was dispersed to produce a positive electrode.

(Ii) 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.

(Iii) 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 (JFC-1500, manufactured by JEOL Ltd.). 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. The unit battery thus obtained was sealed in an exterior material made of an Al laminate film in an Ar atmosphere to obtain an all solid lithium battery.

(Iv) Battery evaluation The obtained all solid lithium battery was charged to 4.2 V at a constant current of 0.1 mA, and then charged at a constant voltage until the current reached 0.005 mA. At that time, a) the voltage did not rise to 4.2V and could not be charged, and b) even if it could be charged, the battery voltage dropped to 4V or less after being left for 12 hours was evaluated as a “defective product” Those that were not evaluated as “good”. This battery evaluation was performed on 10 batteries manufactured in the same manner as described above, and the ratio of non-defective products (that is, yield) to the 10 batteries was calculated. The results were as shown in Table 1.

Examples 2 and 3 : Ti coating treatment A 0.5 mol / L solution obtained by dissolving the LiCoO ₂ oriented sintered plate prepared in Example 1 in 2-methoxyethanol by dissolving Ti isopropoxide (manufactured by Koyo Chemical Co., Ltd.) It was immersed in and dried. Thus 400 ° C. in air for LiCoO ₂ oriented sintered plate coated with Ti precursor (Example 2) or 600 ° C. 5 hours of heat treatment is made in (Example 3), LiCoO ₂ oriented sintered which is Ti coating treatment I got a plate. The same evaluation as in Example 1 was performed for this LiCoO ₂ oriented sintered plate. As a result, in each of Examples 2 and 3, the same XRD profile as in Example 1 was obtained, and it was confirmed that many (104) planes exist in parallel to the plate surface, that is, are oriented. In addition, as shown in Table 1, it can be seen that the proportion of non-defective products in the 10 batteries is significantly improved as compared with Example 1.

Example 4 : Al coating treatment The LiCoO ₂ oriented sintered plate produced in Example 1 was immersed in a 0.1 mol / L solution obtained by dissolving Al isopropoxide (manufactured by Kojundo Chemical Co., Ltd.) in 2-propanol. , Dried. Thus, the LiCoO ₂ oriented sintered plate coated with the Al precursor was heat-treated at 400 ° C. for 5 hours in the air to obtain an Li CoO ₂ oriented sintered plate coated with Al. The same evaluation as in Example 1 was performed for this LiCoO ₂ oriented sintered plate. As a result, the same XRD profile as in Example 1 was obtained, and it was confirmed that many (104) planes exist in parallel to the plate surface, that is, are oriented. In addition, as shown in Table 1, it can be seen that the proportion of non-defective products in the 10 batteries is significantly improved as compared with Example 1.

Example 5 : Zr coating treatment The LiCoO ₂ oriented sintered plate produced in Example 1 was immersed in a 0.5 mol / L solution obtained by dissolving Zr tetrabutoxide (manufactured by Kanto Chemical Co., Inc.) in 2-methoxyethanol. Dried. The LiCoO ₂ oriented sintered plate thus coated with the Zr precursor was heat-treated at 400 ° C. for 5 hours in the atmosphere to obtain a LiCoO ₂ oriented sintered plate coated with Zr. The same evaluation as in Example 1 was performed for this LiCoO ₂ oriented sintered plate. As a result, the same XRD profile as in Example 1 was obtained, and it was confirmed that many (104) planes exist in parallel to the plate surface, that is, are oriented. In addition, as shown in Table 1, it can be seen that the proportion of non-defective products in the 10 batteries is significantly improved as compared with Example 1.

Claims (12)

A method for producing a lithium cobaltate oriented sintered plate used as a positive electrode active material of an all-solid lithium battery, wherein the lithium cobaltate sintered plate is at least one of (104) plane and (101) plane of LiCoO ₂ Is oriented parallel to the plate surface,
(A) preparing a green sheet having a thickness of 100 μm or less, comprising Co ₃ O ₄ particles;
(B) firing the green sheet at 900 to 1400 ° C. to obtain a Co ₃ O ₄ oriented sintered plate having the (h00) plane oriented parallel to the sheet surface;
(C) firing the Co ₃ O ₄ oriented sintered plate in the presence of a lithium source to introduce lithium, thereby forming a lithium cobaltate oriented sintered plate mainly composed of LiCoO ₂ ;
And a solution or slurry of a compound containing at least one additional element selected from the group consisting of Ti, Al and Zr on the surface of the Co ₃ O ₄ oriented sintered plate prior to the step (c) A solution of a compound containing at least one additional element selected from the group consisting of Ti, Al, and Zr on the surface of the lithium cobalt oxide oriented sintered body after the step (d1) of coating with the step (d1) or the step (c) Alternatively, the method further includes a step (d2) of coating the lithium cobalt oxide oriented sintered body coated with a slurry and coated with the solution or the slurry.   The compound is a Ti-containing compound, and the Ti-containing compound is at least one form selected from the group consisting of nitrate, sulfate, acetate, carbonate, chloride, oxide, and alkoxide. The method according to 1.   The compound is an Al-containing compound, and the Al-containing compound is at least one form selected from the group consisting of nitrate, sulfate, acetate, carbonate, chloride, oxide, and alkoxide. The method according to 1.   The compound is a Zr-containing compound, and the Zr-containing compound is in at least one form selected from the group consisting of nitrate, sulfate, acetate, carbonate, chloride, oxide, and alkoxide. The method according to 1.   The method according to any one of claims 1 to 4, wherein the firing in the step (d2) is performed at a firing temperature of 300 to 900 ° C.   The method according to claim 1, wherein the raw material powder further comprises bismuth oxide.   The method as described in any one of Claims 1-6 by which baking in the said (c) process is performed at 600-950 degreeC. The lithium cobalt oxide sintered plate is formed by aligning (104) plane of LiCoO ₂ parallel to the plate plane, and firing in the step (b) is performed at 900 to 1350 ° C. The method as described in any one of -7. A lithium cobaltate oriented sintered plate used as a positive electrode active material of an all-solid-state lithium battery, wherein the lithium cobaltate oriented sintered plate is mainly made of LiCoO ₂ and has a (104) plane of LiCoO ₂ and (101 ) At least one of the surfaces is oriented parallel to the plate surface,
A lithium cobaltate oriented sintered plate, wherein a surface of the lithium cobaltate oriented sintered plate is coated with an oxide containing at least one additional element selected from the group consisting of Ti, Al, and Zr. The lithium cobaltate sintered plate according to claim 9, wherein the lithium cobaltate sintered plate is formed by aligning (104) plane of LiCoO ₂ in parallel with the plate surface. A method for forming a solid electrolyte layer on a lithium cobaltate oriented sintered plate for the production of an all-solid lithium battery,
Preparing a lithium cobaltate oriented sintered plate according to the method according to any one of claims 1 to 8, or preparing a lithium cobaltate oriented sintered plate according to claim 9 or 10, and
Forming a solid electrolyte layer made of a lithium phosphate oxynitride (LiPON) ceramic material on the surface of the lithium cobaltate oriented sintered plate by sputtering;
Including a method.   The method according to claim 11, wherein the solid electrolyte layer has a thickness of 0.1 to 10 μm.