JP5273732B2 - Manufacturing method of ceramic material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a ceramic material providing such the density and dense structure that are available for use in a solid electrolyte material of a lithium secondary battery or the like. <P>SOLUTION: This ceramic material having a crystallographic structure of garnet type or pseudo-garnet type, and containing Li, La, Zr, Al and O is synthesized by firing an Li component, La component, Zr component and Al component in an inert gas atmosphere. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a method for manufacturing a ceramic material, and more particularly to a method for manufacturing a ceramic material for a solid electrolyte suitable for an all-solid lithium secondary battery.

  In recent years, with the development of portable devices such as personal computers and mobile phones, the demand for secondary batteries as a power source has been greatly expanded. In secondary batteries used for such applications, liquid electrolytes (electrolytic solutions) such as organic solvents are widely used as a medium for moving ions. A battery using such an electrolytic solution may cause problems such as ignition and explosion, such as leakage of the electrolytic solution.

  Therefore, from the standpoint of securing intrinsic safety, development of an all-solid secondary battery in which a solid electrolyte is used instead of a liquid electrolyte and all other battery elements are made of solid is being promoted. Since such an all-solid secondary battery is a ceramic in which an electrolyte is sintered, there are advantages that there is no risk of ignition or leakage, and that problems such as deterioration of battery performance due to corrosion hardly occur. Especially, the all-solid-state lithium secondary battery which uses a lithium metal for an electrode is considered as a secondary battery which can be easily made into a high energy density.

  In order to improve the battery characteristics of the secondary battery, it is important to increase the potential difference between the materials used for the positive electrode and the negative electrode and to improve the capacity density of each material used for the positive and negative electrodes. In particular, it has been found that using a Li metal or a Li alloy as a negative electrode material greatly contributes to improvement in characteristics. However, in Li metal, a phenomenon of precipitation of Li metal called dendrite occurs due to the intercalation reaction. Therefore, in the case of a battery using an electrolyte solution in the electrolyte portion, the Li metal deposited in the dendrite breaks through the separator, and the battery It could not be used due to safety issues because it caused a short inside. In an all-solid-state battery in which the electrolyte portion is formed of a solid, it is expected that the deposit cannot penetrate the solid electrolyte and can be used safely. However, since this Li metal has the lowest potential and high reactivity, no applicable solid electrolyte has been found yet.

In recent years, Li ₇ La ₃ Zr ₂ O ₁₂ (hereinafter referred to as LLZ), which is a garnet-type ceramic material, has excellent lithium resistance and has been reported to be usable as a solid electrolyte for an all-solid Li secondary battery. (Non-Patent Document 1).

Ramaswamy Murugan etal., Angew.Chem. Int. Ed. 2007, 46, 1-5

  However, when the present inventors tried to produce an LLZ pellet based on the above non-patent document, it was not possible to obtain an LLZ pellet that could be used as a solid electrolyte of an all-solid lithium secondary battery. It could not be said that the material was practical as a solid electrolyte material for batteries.

  Accordingly, an object of the present invention is to provide a method for producing a ceramic material having a density and a dense structure that can be used as a solid electrolyte material of a lithium secondary battery.

  The present inventors have made various studies on various operations including the raw materials of LLZ ceramics and heat treatment conditions and finally obtained ceramics, and found that raw materials containing aluminum in addition to the above LLZ components are contained in an Ar atmosphere. The knowledge that a good density and a dense structure can be obtained by firing was obtained. According to the present invention, the following means are provided.

  According to the present invention, there is provided a method for producing a ceramic material, in which a Li component, a La component, a Zr component, an Al component, and an O component are baked in an inert gas atmosphere to obtain Li, La, Zr, Al, and O. And a step of synthesizing a ceramic material having a garnet-type or a garnet-type-like crystal structure.

  In the manufacturing method, the gas type of the inert gas is selected from, for example, helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). 1 type (s) or 2 or more types can be included. Ar is preferable. Further, the synthesis step includes a first heat treatment step for obtaining a primary fired powder containing at least a Li component, a La component, and a Zr component, and firing the primary fired powder in the presence of an Al component to obtain the ceramic material. And obtaining a second heat treatment step.

It is a figure which shows the electron microscope observation result of the dense structure of the Li-La-Zr-Al type | system | group ceramic baked in Ar atmosphere and air atmosphere. It is a figure which shows the X-diffraction spectrum of the Li-La-Zr-Al type | system | group ceramic baked in Ar atmosphere. The mark indicates a peak corresponding to the peak identified at 045-0109 of the ICDD powder diffraction file.

  The present invention relates to a method for producing a ceramic material, a ceramic material, and an all solid lithium secondary battery. According to the method for producing a ceramic material of the present invention, a composite oxide having an LLZ crystal structure having a high density and a dense structure by containing an Al component in a ceramic synthesis raw material and further firing such raw material in an inert atmosphere. -Based ceramic materials can be obtained. According to this ceramic material, it is possible to provide a solid electrolyte excellent in lithium resistance and an all-solid-state secondary battery including the solid electrolyte.

  Hereinafter, the ceramic material of the present invention and the manufacturing method thereof will be described, and an all-solid lithium secondary battery using the ceramic material as a solid electrolyte material will be described.

(Ceramic materials)
The ceramic material of the present invention contains Li, La, Zr and Al as constituent metal elements, further contains O, and has a garnet-type or garnet-type similar crystal structure (hereinafter referred to as LLZ crystal structure). It is. The LLZ crystal structure may consist essentially of Li, La, Zr and O.

As a feature of the LLZ crystal structure of the ceramic material of the present invention, as an example of a material having the same garnet-type crystal structure, a powder diffraction file of ICDD (International Center for Diffraction Data) shown below, 045-0109 (Li ₅ La ₃ Nb ₂ O ₁₂ ) has a similar XRD diffraction pattern. Note that, compared with 045-0109, 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 ceramic material of the present invention has a stoichiometric ratio of Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ) described in Non-Patent Document 1 or approximates it so as to have an LLZ crystal structure.

  The ceramic material of the present invention contains Li, La, Zr, Al, and O. According to the present inventors, it has been found that by containing Al, a ceramic having an LLZ crystal structure can be obtained as a sintered pellet that can be handled for the first time. It is preferable that the aluminum content is included within a range in which the sinterability (density of the sintered body) is improved. The density is calculated, for example, by measuring the weight and volume of the pellet. For example, in the case of a cylindrical pellet, after measuring the weight, several parts of the pellet diameter are measured with a micrometer to obtain an average value, and the thickness is similarly measured with the micrometer to calculate the volume. It is preferable to measure by the method of measuring the density from the above or the method of obtaining the same accuracy and accuracy.

  Those skilled in the art will know that the Al content at which such property improvement can be obtained is an appropriate amount for the Li component, La component, and Zr component mixed in an appropriate molar ratio based on the theoretical amount of LLZ and the theoretical amount. By performing a firing step in the presence of an Al component to obtain a sintered body and measuring its characteristics, it is possible to easily determine the Al content according to the application. As an example, it has been found that an improved density can be obtained when 0.1 mass% or more of Al is contained with respect to the total weight of the finally obtained ceramic powder and sintered pellets. Moreover, it has also been found that the density greatly exceeding 2% by mass tends to decrease, and preferably 1.5% by mass or less. More preferably, Al content is 0.31 mass% or more and 1.38 mass% or less with respect to the total weight, More preferably, it is 0.45 mass% or more and 1.32 mass% or less. More preferably, it is about 0.73 mass%.

  The form of Al in the ceramic material of the present invention is not particularly limited as long as it can observe a single-phase LLZ crystal and can be confirmed to contain aluminum by ICP emission spectroscopic analysis. In addition, according to the present inventors, it is known that Al exists in crystal grains.

  Al in the ceramic material of the present invention can be detected, for example, by ICP (high frequency inductively coupled plasma) emission spectroscopic analysis and the content thereof can be determined.

  The ceramic material of the present invention may be a ceramic powder or a sintered body as long as it contains Li, La, Zr, Al and O and has an LLZ crystal structure. The solid electrolyte of the all-solid lithium secondary battery is preferably a sintered body. A material for obtaining such a solid electrolyte is preferably a powder.

  The ceramic material of the present invention containing aluminum and having improved sinterability (density) in the sintered body is preferable as a solid electrolyte material for an all-solid lithium secondary battery. Moreover, it can use preferably for the oxygen sensor material using conductivity.

The ceramic material of the present invention can have a high density. For example, a density of 4.6 g / cm ³ or more can be provided. By providing a high density, handling is also improved. More preferably, it is 4.7 g / cm ³ or more.

(Manufacturing method of ceramic material)
The method for producing a ceramic material of the present invention includes a Li component, a La component, a Zr component, an Al component, and an O component fired in an inert gas atmosphere, and includes Li, La, Zr, Al, and O. A step of synthesizing a ceramic material having a garnet-like crystal structure can be provided.

(Preparation of raw materials)
Examples of the raw material for the ceramic material of the present invention include a Li component, a La component, a Zr component, an Al component, and an O component. The O component is usually included as a part of the constituent metal element component.

(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.

(Al component)
The Al component is not particularly limited, and various metal salts such as metal oxides, metal hydroxides, metal nitrates, metal organics, and simple metals containing Al can be appropriately selected and used. For example, Al ₂ O ₃ , Al (NO ₃ ) ₃ · 9H ₂ O, Al (OH) ₃ , Al, aluminum acetylacetonate, aluminum triethoxide, aluminum butoxide, aluminum propoxide, aluminum methoxide, aluminum chloride, Aluminum chloride hexahydrate, diethyl aluminum chloride, aluminum oleate, aluminum acetate n hydrate, aluminum oxalate, aluminum bromide hexahydrate, aluminum stearate, triethyl aluminum, trimethyl aluminum, triisobutyl aluminum, aluminum sulfate Aluminum iodide or the like can be used. The Al component is present with respect to the Li component, the La component, and the Zr component within a range where improvement in sinterability can be obtained by including Al. Moreover, it is preferable that the ceramic material of the present invention is prepared in a range where an LLZ crystal structure can be obtained.

These components for obtaining the ceramic material of the present invention are prepared by mixing Li component, La component, and Zr component based on the theoretical amount ratio of Li ₇ La ₃ Zr ₂ O ₁₂ (LLZ) described in Non-Patent Document 1. can do. For example, the Li component, La component, and Zr component can be used in accordance with the stoichiometric composition of LLZ, Li component: La component: Zr component = 7: 3: 2 or a composition that approximates the composition. In preparing each component, the Li component may be increased to about 10% in consideration of the volatilization of Li during heat treatment. Further, in the ceramic material of the present invention, the loss of the powder during the pulverization and recovery of the synthetic powder occurs, so that each element of Li, La, Zr and O may deviate from the composition of the chemical formula of Non-Patent Document 1. know.

  The Al component in the raw material is not particularly limited. The content of the Al component that can improve the sinterability is appropriate for those skilled in the art to the theoretical amount of LLZ and the Li component, La component, and Zr component mixed at an appropriate molar ratio based on the theoretical amount. By performing the firing step in the presence of an amount of Al component to obtain a sintered body and measuring its characteristics, the Al content corresponding to the application can be easily determined. As an example, a preferable Al content with respect to the total weight of the present ceramic material finally obtained as described above (for example, 0.1% by mass to 0.2% by mass, more preferably 1.5% by mass) More preferably, it is 0.31 mass% or more and 1.38 mass% or less, More preferably, it is 0.45 mass% or more and 1.32 mass% or less, More preferably, it is about 0.73. The Al component is used so as to obtain (mass%).

  Each of these components can be used without particular limitation as long as it is industrially produced and available. The purity is preferably 95% or more, and more preferably 98% or more. Moreover, it is preferable that a water | moisture content is 1% or less, and you may dry as needed.

  In preparing the raw material, 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.

(Synthesis process)
The synthesis step includes firing Li, La, Zr, and Al components as constituent metal elements in a inert gas atmosphere, and containing Li, La, Zr, Al, and O. This is a step of synthesizing a ceramic material having a garnet type or garnet type-like crystal structure. In this synthesis step, the ceramic material of the present invention may be synthesized all at once from a raw material containing these components. As the synthesis method, various known ceramic synthesis methods can be employed. The firing temperature for synthesis is not particularly limited, but is preferably 1000 ° C. or higher, more preferably heat treatment at a temperature of 1125 ° C. or higher and 1250 ° C. or lower. The ceramic material is preferably subjected to a heat treatment for synthesis in an inert gas atmosphere, but calcination treatment such as a decomposition reaction of the raw material in the previous stage may be performed in an oxidizing atmosphere.

  Further, the synthesis process may be a combination of two or more heat treatment processes. That is, the synthesis step includes a first heat treatment step for obtaining a primary firing powder containing at least a Li component, a La component, a Zr component and other O components as constituent metal elements, and firing the primary firing powder in the presence of an Al component. And a second heat treatment step for obtaining the ceramic material. Such a combination of heat treatment steps makes it easy to obtain a high density and an LLZ crystal structure.

  The synthesis process of the ceramic material of the present invention can be performed in an inert gas atmosphere. In synthesizing the ceramic material of the present invention, a higher density can be obtained by heat treatment in an inert gas atmosphere. When heat-treating in an inert gas atmosphere, the raw material is preferably a powder such as an oxide. Therefore, it is preferable to perform at least the second heat treatment step in an inert gas in the first heat treatment step and the second heat treatment step described later. Examples of the inert gas species include one or more selected from helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). be able to. Ar is preferable.

(First heat treatment step)
The first heat treatment step is a step of obtaining a primary fired powder for making it easy to synthesize a ceramic material in the second heat treatment step by thermally decomposing at least a Li component or a La component. The firing temperature is preferably 850 ° C. or higher and 1150 ° C. or lower. The first heat treatment 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 heat treatment step. When the first heat treatment 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 completion of each heating step. Further, it is desirable that the pulverization method is dry. This makes it easier to obtain a more uniform LLZ phase by the second heat treatment step. Depending on the conditions of the first heat treatment step, the primary fired powder may already have an LLZ crystal structure.

  The first heat treatment step may be performed in an oxidizing atmosphere such as air or in an inert atmosphere. The preferable atmosphere varies depending on the raw material. Considering thermal decomposition, an oxidizing atmosphere is preferable.

  The heating step constituting the first heat treatment step is preferably performed by a heating step of 850 ° C. or higher and 950 ° C. or lower and a heating step of 1075 ° C. or higher and 1150 ° C. or lower. More preferably, a heating step of 875 ° C. or more and 925 ° C. or less (more preferably about 900 ° C.) and a heating step of 1100 ° C. or more and 1150 ° C. or less (more preferably about 1125 ° C.) are used.

In the first heat treatment step, the total heating time at the highest temperature set as the heating temperature as a whole is preferably about 10 hours to 15 hours. When the first heat treatment step is composed of two heat treatment steps, it is preferable to set the heating time at the maximum temperature to about 5 to 6 hours.
On the other hand, the first heat treatment step can be shortened by changing the raw material. For example, when LiOH is used for the Li component, in order to obtain an LLZ crystal structure, the raw material containing the Li component, La component and Zr component is heated at a maximum temperature of 10 hours or less in a heat treatment step of 850 ° C. or more and 950 ° C. or less. Can be. This is because LiOH used as a raw material forms a liquid phase at a low temperature, and thus easily reacts with other raw materials at a lower temperature.

  The raw material used in the first heat treatment step may contain an Al component. When the raw material contains an Al component, a primary fired powder containing Al can be obtained. For this reason, in the subsequent second firing step, the Al component is inherent in the primary fired powder without separately adding an Al component to the primary fired powder, and the second fired heat treatment is performed on the primary fired powder. By carrying out the process, the primary fired powder is heat-treated in the presence of the Al component without adding an additional Al component.

(Second heat treatment step)
The second heat treatment step can be a step of heating the primary fired powder obtained in the first heat treatment step at a temperature of 950 ° C. or higher and 1250 ° C. or lower. According to the second heat treatment step, the primary fired powder obtained in the first heat treatment step can be fired to finally obtain the ceramic material of the present invention.

In the second heat treatment step, the primary fired powder is preferably heat treated at a temperature of 1125 ° C. or higher and 1250 ° C. or lower. This makes it easier to obtain an LLZ crystal structure. When LiCO ₃ is used as the Li component, heat treatment is preferably performed 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., formation of a different phase (such as La ₂ Zr ₂ O ₇ ) is observed and the Li ion conductivity is low. In addition, 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 heat treatment step can be lowered by changing the raw material components. For example, when LiOH is used as the Li component, the primary fired powder can be heat-treated at a temperature of 950 ° C. or higher and lower than 1125 ° C. to obtain an LLZ crystal structure. This is because LiOH used for the Li component forms a liquid phase at a low temperature, and thus easily reacts with other raw material components at a lower temperature.

  The heating time at the heating temperature in the second heat treatment step is preferably about 18 hours to 50 hours. This is because when the time is shorter than 18 hours, the formation of the LLZ crystal structure is not sufficient, and when the time is longer than 50 hours, the crystal growth is not able to maintain the strength as a sample. It is preferably longer than 18 hours, more preferably 30 hours or longer.

  The second heat treatment step can be performed in an air atmosphere, but is preferably performed in an inert gas atmosphere. A high density can be obtained by heating the primary fired powder in an inert gas atmosphere.

  In the second heat treatment step, a material containing the primary fired powder is pressure-molded by using a known press technique to obtain a desired three-dimensional shape (for example, a shape and size that can be used as a solid electrolyte of an all-solid secondary battery). It is preferable to carry out after forming a molded body to which is provided. By using a molded body, a solid phase reaction is promoted, and a dense sintered body is easily obtained. In addition, after the second heat treatment step, the sintering step may be separately performed at the same temperature as the heating temperature in the second firing step using the ceramic powder obtained in the second heat treatment step as a molded body.

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. 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 second heat treatment step is performed at a low temperature by using LiOH as a Li component, the molded body of the primary fired powder can be sintered without being embedded in the same powder. This is because the loss of Li is relatively suppressed by lowering the temperature of the second heat treatment step.

  In order to perform the second heat treatment step in the presence of the Al component, the primary fired powder obtained by performing the first heat treatment step in the presence of the Al component is used as it is in the second heat treatment step. An embodiment in which the second heat treatment step is performed by adding and mixing the Al component to the primary fired powder obtained by performing the first heat treatment step in the absence of the Al component. In order to perform the second heat treatment step in the presence of the Al component, any of these forms may be used, or these forms may be appropriately combined. Preferably, the Al component is present in the second heat treatment step, particularly in the step involving sintering. By doing so, good sinterability can be obtained.

  According to the above synthesis process, the ceramic material of the present invention can be obtained. Moreover, as a ceramic material, it can obtain as a powder or a sintered compact. In the method for producing a ceramic material of the present invention, since the Al component is baked in an inert atmosphere in addition to the Li component, La component, and Zr component contained in the LLZ crystal structure, the sinterability is improved, so that the high density A sintered body having a dense structure can be obtained. Furthermore, since the heating temperature is also lower than in the prior art, the energy cost for obtaining the solid electrolyte material of the all-solid lithium secondary battery can be reduced. Furthermore, the ceramic material of the present invention can be obtained reliably by carrying out the first heat treatment step and the second heat treatment step.

(All-solid lithium secondary battery)
The all-solid lithium secondary battery of the present invention can include a positive electrode, a negative electrode, and a solid electrolyte containing Li, La, Zr, Al, and O and having an LLZ crystal structure. The all-solid lithium secondary battery of the present invention includes a solid electrolyte excellent in lithium resistance, and is a practical secondary battery as compared with the prior art.

  In the secondary battery of the present invention, it is preferable to use the sintered body obtained by the method for producing a ceramic material of the present invention as it is or without being pulverized and used as a solid electrolyte. In addition, the molded object containing the ceramic material of this invention and another component may be obtained using the powder baked in the powder state in the second baking step, and this molded object may be used as a solid electrolyte. A conventionally known method for producing a ceramic molded body can be applied to the method for producing the molded body. Examples thereof include molding methods such as a press method, a doctor blade method, and a roll coater method.

  The positive electrode and negative electrode of the all solid lithium secondary battery of the present invention can contain conventionally known positive electrode active materials and negative electrode active materials used in lithium secondary batteries, and are produced by a conventional method.

(Positive electrode active material)
There is no restriction | limiting in particular as a positive electrode active material, The positive electrode active material used for a conventionally well-known all-solid-state battery can be used. In particular, when a metal oxide is used as the positive electrode active material, the secondary battery can be sintered in an oxygen atmosphere. Specific examples of such a positive electrode active material include manganese dioxide (MnO ₂ ), iron oxide, copper oxide, nickel oxide, lithium manganese composite oxide (for example, Li _x Mn ₂ O ₄ or Li _x MnO ₂ ), and lithium nickel composite. Oxide (for example, Li _x NiO ₂ ), lithium cobalt composite oxide (for example, Li _x CoO ₂ ), lithium nickel cobalt composite oxide (for example, LiNi _1-y Co _y O ₂ ), lithium manganese cobalt composite oxide _{(e.g., LiMn y Co 1-y O} 2), lithium manganese cobalt nickel complex oxide _{(e.g., LiMn x Co y Ni z O} 2), spinel type lithium-manganese-nickel composite oxide _(e.g., Li x _{Mn 2-y} Ni _y O _4), lithium phosphate compounds having an olivine structure (for example, _{i x FePO 4, Li x Fe} 1-y Mn y PO 4, Li x CoPO 4), lithium phosphate compounds having a NASICON structure _{(e.g., Li x V 2 (PO 4} ) 3), iron sulfate _(Fe 2 ( SO ₄ ) ₃ ), vanadium oxide (for example, V ₂ O ₅ ) and the like. These may be used alone or in combination of two or more. In these chemical formulas, x and y are preferably in the range of 1 <x <5, 0 <y <1. Among these, LiCoO ₂ , Li _x NiO ₂ , Li _x V ₂ (PO ₄ ) ₃ , LiNPO ₄ , and LiFePO ₄ are preferable.

(Negative electrode active material)
There is no restriction | limiting in particular as a negative electrode active material, The negative electrode active material used for a conventionally well-known all-solid-state battery can be used. For example, carbon, metal lithium (Li), metal compound, metal oxide, Li metal compound, Li metal oxide (including lithium-transition metal composite oxide), boron-added carbon, graphite, compound having NASICON structure, etc. Can be mentioned. These may be used alone or in combination of two or more. For example, when the metal lithium (Li) is used, the capacity of the all solid state battery can be increased. Examples of the carbon include conventionally known carbon materials such as graphite carbon, hard carbon, and soft carbon. Examples of the metal compound include LiAl, LiZn, Li ₃ Bi, Li ₃ Cd, Li ₃ Sd, Li ₄ Si, Li _4.4 Pb, Li _4.4 Sn, and Li _0.17 C (LiC ₆ ). be able to. The metal _{oxides, SnO, SnO 2, GeO,} GeO 2, In 2 O, In 2 O 3, PbO, PbO 2, Pb 2 O 3, Pb 3 O 4, Ag 2 O, AgO, Ag 2 O ₃ , Sb ₂ O ₃ , Sb ₂ O ₄ , Sb ₂ O ₅ , SiO, ZnO, CoO, NiO, TiO ₂ and FeO. Examples of the Li metal compound include Li ₃ FeN ₂ , Li _2.6 Co _0.4 N, Li _2.6 Cu _0.4 N, and the like. Examples of the Li metal oxide (lithium-transition metal composite oxide) include a lithium-titanium composite oxide represented by Li ₄ Ti ₅ O ₁₂ . Examples of the boron-added carbon include boron-added carbon and boron-added graphite. Preferably, it is metallic lithium.

  In addition, in order to obtain a positive electrode and a negative electrode, in addition to the above-described active materials, a positive electrode material or a negative electrode material containing an electron conduction assistant or a binder may be prepared in advance. Examples of the electron conduction aid include acetylene black, carbon black, graphite, various carbon fibers, and carbon nanotubes. Examples of the binder include polyvinylidene fluoride (PVDF), SBR, polyimide, polytetrafluoroethylene, and the like. Moreover, these active materials can be used alone or in combination of two or more for the positive electrode.

  The positive electrode and the negative electrode included in the all solid lithium secondary battery may be in any form as long as it functions as a secondary battery. The above-described positive electrode active material or positive electrode material or negative electrode active material or negative electrode material can be formed into a molded body using a known molding method such as a press method, a doctor blade method, or a roll coater method. In the pressing method, a molded body can be obtained by filling a positive electrode active material powder or negative electrode active material powder in a mold or the like and pressurizing it. On the other hand, in the doctor blade method and the roll coater method, first, a positive electrode active material or a negative electrode active material and a binder such as polyvinyl alcohol are mixed to obtain a mixture. An appropriate amount of solid electrolyte may be added to the mixture as necessary. Next, an organic solvent such as toluene is added to the obtained mixture to prepare a positive electrode slurry. The prepared positive electrode slurry is formed into a thin film or sheet having a predetermined thickness by a forming method such as a doctor blade method or a roll coater method. After drying, the positive electrode and the negative electrode can be produced by performing processing such as cutting as necessary and firing. Moreover, it is good also as a molded object which included the said various active materials and the powder of the ceramic material of this invention suitably as a positive electrode and a negative electrode.

  The cell of the all-solid lithium secondary battery of the present invention is produced by combining a solid electrolyte with the positive electrode material or positive electrode, negative electrode material or negative electrode prepared as described above. Production of the cell differs depending on the battery form to be finally obtained. For example, a positive electrode material is applied to one surface of the solid electrolyte to form a positive electrode, and a negative electrode material is applied to the other surface of the solid electrolyte. It can be a negative electrode or the like. In addition, the cell structure of the all-solid-state secondary battery of the present invention is not particularly limited. For example, in addition to a coin type, various battery types such as a cylindrical type and a box type may be used.

  In addition, from the above description, the present invention provides a process for obtaining an LLZ sintered body by heat-treating the raw material powder, and combining the positive electrode and the negative electrode with the sintered body as a solid electrolyte. It can implement also as a manufacturing method of an all-solid-state lithium secondary battery provided with the process of producing a cell.

  Hereinafter, the present invention will be described with reference to examples. The following examples are provided to illustrate the present invention and are not intended to limit the present invention.

(Synthesis of Al-containing Li-La-Zr ceramics)
(Preparation of raw materials for Example samples)
As starting materials, lithium hydroxide, lanthanum hydroxide (Shin-Etsu Chemical Co., Ltd.), and zirconium oxide (Tosoh Corporation) were used. These powders were weighed in molar ratios such that LiOH: La (OH) ₃ : ZrO ₂ : = 7: 3: 2. These powders were mixed with a lykai machine to obtain raw material powders. When the composition of Li, La, and Zr in the raw material powder is expressed by a composition formula, Li ₇ La ₃ Zr ₂ is obtained.

(First heat treatment process)
The raw material powder was put in a crucible, heated in the atmosphere at 600 ° C./h, and held at 900 ° C. for 6 h.
(Second heat treatment process)
After the previous heat treatment, the heat-treated powder and cobblestone were mixed and pulverized for 3 hours using a vibration mill. After pulverization, the powder was passed through a sieve, and γ-Al ₂ O ₃ was added to the powder so as to be 1.5 mass% of the total weight of the powder.

  After these various powders were press-molded using a mold, the pellets were placed on a setter, the setter was placed in a sheath, and the temperature was raised at 200 ° C./h, and an air atmosphere and an Ar atmosphere (purity 99.99). 999%) for 36 hours at 1000 ° C. to obtain sintered pellets. The upper and lower surfaces of the sintered pellets were polished, and the structure was evaluated as follows.

(Structural evaluation)
The microstructure of each pellet was observed with an electron microscope. The results are shown in FIG. Moreover, the X-ray diffraction measurement of each pellet was performed. The results are shown in FIG. Furthermore, after measuring the weight of the pellet, measure the pellet diameter using a micrometer and calculate the average value, then measure the pellet thickness in the same way to calculate the volume of the pellet, and calculate the density did.

The density of the pellet obtained by firing in the air atmosphere was 4.54 g / cm ³ , whereas the density of the pellet obtained by firing in the Ar atmosphere was 4.71 g / cm ³ . That is, by firing in an Ar atmosphere, the sinterability was improved, and higher density pellets could be obtained. Moreover, as shown in FIG. 1, it turned out that the microstructure is also densified by baking in Ar atmosphere.

  Furthermore, as shown in FIG. 2, a diffraction pattern similar to ICDD powder diffraction file 045-0109 can be obtained by X-ray diffraction measurement for pellets fired in an Ar atmosphere, and these pellets have an LLZ crystal structure. I found out.

  From the above, it was found that a high-density and dense LLZ crystal structure can be obtained by firing a raw material containing an Al component in addition to a Li component, a La component, and a Zr component in an Ar atmosphere.

Claims (3)

A method of manufacturing a ceramic material,
Ceramics containing Li, La, Zr, Al and O and having a garnet-type or similar garnet-type crystal structure by firing Li, La, Zr, Al and O components in an inert gas atmosphere Synthesizing materials,
A manufacturing method comprising:   The manufacturing method according to claim 1, wherein a gas type of the inert gas is Ar.   In the synthesis step, a first heat treatment step for obtaining a primary fired powder containing at least a Li component, a La component, a Zr component, and an O component, and firing the primary fired powder in the presence of an Al component, the ceramic material The manufacturing method of Claim 1 or 2 including the 2nd heat treatment process of obtaining.