JP2019046559A - Method for manufacturing solid electrolyte, method for manufacturing all-solid battery electrode material, and method for manufacturing all-solid battery - Google Patents

Abstract

To manufacture a solid electrolyte consisting of LAGP suitable for formation of a coat on an electrode active material according to a simple procedure more inexpensively.SOLUTION: A method for manufacturing a solid electrolyte represented by the general formula, LiAlGe(PO), where 0<x≤1 comprises: an ammonia concentration-adjusting step (s3) of using GeOand a plurality of water-soluble compounds as raw material, adding ammonia to a mixture solution obtained in the step (s2) of mixing GeOin water to dissolve GeOin the solution and to obtain a first liquid solution, and adjusting an ammonia concentration of the first liquid solution to a concentration which causes all of water-soluble compounds to dissolve therein; a step (s4) of mixing in the first liquid solution with a plurality of water-soluble compounds to obtain a second liquid solution; a vitrification step (s7) of performing a thermal treatment of the second liquid solution to obtain an amorphous solid electrolyte; and a baking step (s8) of baking the amorphous solid electrolyte to cause crystallization of LAGP.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of producing a solid electrolyte, a method of producing an electrode material for an all solid battery, and a method of producing an all solid battery.

  Lithium secondary batteries are known for having high energy density among various secondary batteries. However, since lithium secondary batteries in widespread use use a flammable organic electrolyte as an electrolyte, in lithium secondary batteries, safety measures against liquid leakage, short circuit, overcharge, etc. are stricter than other batteries. It has been demanded. Therefore, in recent years, research and development on an all-solid-state battery using an oxide-based or sulfide-based solid electrolyte as an electrolyte has been actively conducted. The solid electrolyte is a material mainly composed of an ion conductor capable of ion conduction in a solid, and in principle causes various problems due to the flammable organic electrolyte as in the conventional lithium secondary battery do not do. An all-solid-state battery is an integral sintered body (hereinafter, a laminated electrode body) in which a layered solid electrolyte (electrolyte layer) is sandwiched between a layered positive electrode (positive electrode layer) and a layered negative electrode (negative electrode layer). Also has a structure in which a current collector is formed.

  As a method of manufacturing a laminated electrode body, there is a method of firing a molded body obtained by pressurizing raw material powder using a mold (hereinafter, also referred to as compression molding method) or a method of using a known green sheet (hereinafter, green Sheet method etc. In the compression molding method, the raw material powder of each layer of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer is sequentially filled in a layer form in a mold, and a molded body obtained by uniaxially pressing is fired to form a laminated electrode body. Get

  In the green sheet method, a slurry-like positive electrode layer material containing a positive electrode active material and a solid electrolyte, a slurry-like negative electrode layer material containing a negative electrode active material and a solid electrolyte, and a slurry-like solid electrolyte layer material containing a solid electrolyte The green sheet is formed into a shape (green sheet), and the laminated body in which the green sheet of the solid electrolyte layer material is held between the positive electrode layer material and the green sheet of the negative electrode layer material is fired to prepare a sintered body. The solid electrolyte contained in the positive electrode layer and the negative electrode layer (hereinafter also referred to as an electrode layer) intervenes between particles of the powdery positive electrode active material and the negative electrode active material to cause the electrode layer to exhibit ion conductivity. It is responsible for the function.

Materials used for conventional lithium secondary batteries can be used as the positive electrode active material and the negative electrode active material (hereinafter collectively referred to as electrode active material). In addition, since an all solid battery does not use a flammable electrolyte, research has also been conducted on an electrode active material that can obtain a higher potential difference. The solid electrolyte has the formula _{Li a X b Y c P d} O e with NASICON type oxide-based solid electrolyte represented, as the solid electrolyte of the NASICON type _{oxide, Li 1 + x Al x Ge} 2 _{-x (PO 4) 3} (where, 0 <x ≦ 1, hereinafter also referred to as LAGP) are well known. Patent Document 1 below describes LAGP at x = 0.5, and LAGP is generally produced by a solid phase method in which a powdery raw material containing a plurality of compounds is fired at a high temperature. It is In addition, as a manufacturing method of LAGP, there is another well-known sol-gel method using a metal alkoxide as a raw material, and the following Non-Patent Document 1 describes a manufacturing method of LAGP by the sol-gel method. In addition, Patent Document 2 below describes a method of forming a film having ion conductivity on the surface of an electrode active material.

Unexamined-Japanese-Patent No. 2013-45738 International Publication No. 2014/003036

Masashi Kotobuki, Keigo Hoshina, Yasuhiro Isshiki, Kiyoshi Kanamura, "PREPARATION OF Li 1.5 Al 0.5 Ge 1.5 (PO4) 3 SOLID ELECTROLYTE BY SOL-GEL METHOD", Phosphorus Research Bulletin, Vol. 25 (2011), pp. 061- 063

  The laminated electrode body which is the basic composition of the all solid battery consists of a sintered compact of the structure which clamped the solid electrolyte layer by the positive electrode layer and the negative electrode layer. As described above, the solid electrolyte is contained not only in the solid electrolyte layer but also in the electrode layer. And in order to raise the ion conductivity of an electrode layer, it is more preferable not to interpose the particle | grains of a solid electrolyte between the particle | grains of an electrode active material, but to form the film of a solid electrolyte on the particle | grain surface of an electrode active material. And, since LAGP expresses ion conductivity by being crystallized by firing, in order to form a film of LAGP on the particle surface of the electrode active material, the powder material in the electrode layer before firing (hereinafter referred to as It is necessary to include LAGP in an amorphous state in the electrode material).

  However, when forming a coating of LAGP on the particle surface of the electrode active material using the solid phase method, firing the electrode material in which the powdery amorphous LAGP and the powdery electrode active material are mixed Therefore, it is difficult to mix different powder materials extremely uniformly. If the different powder materials are not uniformly mixed, a bias may occur in the ion conductivity in the electrode layer.

  On the other hand, in the sol-gel method, after mixing a sol containing a metal alkoxide as a raw material and an electrode active material, the sol is gelled, and further, LAGP crystals are formed by firing amorphous LAGP generated by heat treatment. obtain. And when forming the film of LAGP on the particle | grain surface of an electrode active material using a sol gel method, the raw material of LAGP and an electrode active material can be mixed before an amorphous LAGP is produced | generated. Therefore, the film of amorphous LAGP can be effectively formed on the particle surface of the metal active material.

  However, when LAGP is produced using a sol-gel method, the cost of the raw material is increased because an expensive metal alkoxide is used as the raw material. Further, since the metal alkoxide reacts with water, it is necessary to prepare a compound to be a coating layer in a dry atmosphere in order to suppress the reaction. Therefore, in order to manufacture LAGP by a sol-gel method, or to form a film of LAGP on the particle surface of the electrode active material, the cost for the manufacturing facility also increases.

  Therefore, according to the present invention, a solid electrolyte composed of LAGP suitable for forming a coating on an electrode active material contained in an electrode layer of an all solid battery, and a coating of a solid electrolyte consisting of LAGP on the particle surface of the electrode active material It is an object of the present invention to provide an all-solid-state battery electrode material and a method for producing the all-solid-state battery more inexpensively by a simple procedure.

One embodiment of the present invention for achieving the above object is a method of producing a solid electrolyte represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ , wherein 0 <x ≦ 1.
Using GeO ₂ and several water soluble compounds as raw materials,
Mixing the GeO ₂ in water with a first mixing step;
Ammonia concentration adjusting step of adding ammonia to the mixed solution obtained in the first mixing step to dissolve the GeO ₂ in the solution to obtain a first solution and adjusting the ammonia concentration of the first solution; ,
A second mixing step of mixing the plurality of water-soluble compounds into the first solution to obtain a second solution;
Heat treating the second solution to obtain an amorphous solid electrolyte;
Firing the amorphous solid electrolyte to crystallize LAGP;
Including
In the ammonia concentration adjusting step, the ammonia concentration of the first solution is adjusted to a concentration at which all the water soluble compounds are dissolved.
The method for producing a solid electrolyte is characterized by

In the method for producing a solid electrolyte,
The plurality of compounds are CH ₃ COOLi · 2H ₂ O, Al (NO ₃ ) ₃ · 9H ₂ O, NH ₄ H ₂ PO ₄ ,
In the ammonia concentration adjusting step, the ammonia concentration of the first solution is adjusted to 0.2 M or more and 1.35 M or less.
It can also be a method of producing a solid electrolyte.

In the embodiment of the present invention, the solid electrolyte represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ is coated on the particle surface of the electrode active material for an all solid battery, where 0 <x ≦ 1. Also included is a method of producing an electrode material, the method of producing the electrode material comprising
Using GeO ₂ and a plurality of water-soluble compounds as the material of the solid electrolyte,
Mixing the GeO ₂ in water with a first mixing step;
Ammonia concentration adjusting step of adding ammonia to the mixed solution obtained in the first mixing step to dissolve the GeO ₂ in the solution to obtain a first solution and adjusting the ammonia concentration of the first solution; ,
A second mixing step of mixing the plurality of water-soluble compounds into the first solution to obtain a second solution;
An active material mixing step of mixing the powdered electrode active material with the second solution;
Heat treatment at a temperature lower than a calcination temperature at which the solid electrolyte crystallizes, the mixture liquid obtained in the active material mixing step to obtain an amorphous solid electrolyte;
Including
In the ammonia concentration adjusting step, the ammonia concentration of the first solution is adjusted to a concentration at which all the water soluble compounds are dissolved.
The method for producing an electrode material for an all-solid-state battery is characterized by

Further, another aspect of the present invention is an integral sintered body, a positive electrode layer including an electrode active material for a positive electrode and a solid electrolyte, a solid electrolyte layer including a solid electrolyte, and an electrode active material and a solid electrolyte for a negative electrode. A method for producing an all-solid-state battery comprising a laminated electrode body in which a negative electrode layer containing
A positive electrode material in which the solid electrolyte in an amorphous state and the electrode active material for the positive electrode are mixed by using the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ as the solid electrolyte, where 0 <x ≦ 1. And an electrode material preparation step of preparing a negative electrode material in which the solid electrolyte in an amorphous state and an electrode active material for the negative electrode are mixed.
A firing step of producing the laminated electrode body by firing a laminated body formed by sandwiching a layered solid electrolyte material containing the solid electrolyte between the layered positive electrode material and the layered negative electrode material;
Including
In the electrode material preparation step,
A solid electrolyte preparation step of preparing a solid electrolyte using GeO ₂ and a plurality of water soluble compounds as a raw material by a solution method;
An active material mixing step of mixing a powdered electrode active material with the raw material in the process of manufacturing the solid electrolyte by the solid electrolyte manufacturing step;
Run
In the solid electrolyte preparation step,
Mixing the GeO ₂ in water with a first mixing step;
Ammonia concentration adjusting step of adding ammonia to the mixed solution obtained in the first mixing step to dissolve the GeO ₂ in the solution to obtain a first solution and adjusting the ammonia concentration of the first solution; ,
A second mixing step of mixing the plurality of water-soluble compounds into the first solution to obtain a second solution;
Heat treating the second solution at a temperature lower than a calcination temperature at which the solid electrolyte crystallizes to obtain an amorphous solid electrolyte;
Including
In the ammonia concentration adjusting step, the ammonia concentration of the first solution is adjusted to a concentration at which all the water-soluble compounds dissolve.
Performing the active material mixing step between the second mixing step and the vitrification step;
It is considered as the manufacturing method of the all-solid-state battery characterized by the above.

  According to the present invention, a solid electrolyte consisting of LAGP suitable for forming a film on the electrode active material contained in the electrode layer of the all solid battery, and a solid electrolyte film consisting of LAGP on the particle surface of the electrode active material are formed An all-solid-state battery electrode material and a method for producing the all-solid-state battery less expensively by a simple procedure are provided. Other effects will be clarified in the following description.

It is a figure which shows the manufacturing method of the solid electrolyte which concerns on the 1st Example of this invention. It is a figure which shows the XRD measurement result of the solid electrolyte produced by the method concerning the said 1st Example. It is a figure which shows the ion-conductive characteristic of the solid electrolyte produced by the method concerning the said 1st Example. It is a figure which shows an example of the procedure which manufactures the electrode material for all-solid-state batteries using the method concerning the said 1st Example. It is a figure which shows the manufacturing method of the electrode material for all the solid batteries which concern on the 2nd Example of this invention. It is a figure which shows the XRD measurement result of the electrode material for all-solid-state batteries produced using the procedure shown in FIG. It is a figure which shows the XRD measurement result of the electrode material for all-solid-state batteries which concerns on the said 2nd Example.

  In order to realize a practical all-solid-state battery, it is necessary to make LAGP formed as a film on the surface of the electrode active material cheaper by a simpler method. In order to meet such requirements, in the examples of the present invention, LAGP is prepared using a method called solution method or liquid phase method (hereinafter sometimes referred to as solution method). And, in this embodiment, while using water as the initial solvent, the solvent is modified in the order of mixing the raw materials with the solvent and in the process of mixing. Thereby, all the raw materials can be dissolved in the solvent to produce single phase LAGP.

And, in a specific example shown below, germanium dioxide (GeO ₂ : manufactured by High Purity Chemical Laboratory Co., Ltd.), lithium acetate (CH ₃ COOLi · 2H ₂ O: Wako Pure Chemical Industries, Ltd.) as a compound to be a raw material of LAGP Manufactured by Kogyo Co., Ltd., aluminum nitrate (Al (NO ₃ ) ₃ 9 H ₂ O: manufactured by Kanto Chemical Industry Co., Ltd.), ammonium dihydrogen phosphate (NH ₄ H ₂ PO ₄ : manufactured by Kanto Chemical Industry Co., Ltd.) It is supposed to be.

=== Basic Example ===
In order to make it possible to produce LAGP by the above-mentioned raw material and solution method, first, the solubility of each raw material in water was examined. Then, based on the solubility of each compound in water and various solvents, the order of mixing the compounds in the solvent was determined. The presence or absence of solubility in a solvent such as water was visually determined. When the compound is dissolved in the solvent, it becomes a colorless and transparent solution, but if it does not dissolve, the compound precipitates and the solvent becomes cloudy. And, only GeO ₂ among the above-mentioned raw materials was not soluble in water and was poorly soluble in water. Further, the raw material of LAGP including GeO ₂ were all found to be dissolved by the alkaline solvent.

Therefore, in the embodiment of the present invention, GeO ₂ is first mixed with water, and the water is modified to be alkaline to dissolve GeO ₂ . Then, it was decided to dissolve the other compound in the water after modification. Here, each raw material was dissolved in ammonia water. Ammonia water can be easily adjusted to a predetermined ammonia concentration by dissolving ammonia in water, which is the initial solvent, or mixing high concentration ammonia water with water. Also, ammonia and ammonia water are easily available and inexpensive. From the above, the method for producing a solid electrolyte (hereinafter also referred to as LAGP) according to the basic embodiment of the present invention first mixes GeO ₂ with water, and makes the water ammonia water to dissolve GeO ₂ On top of that, other LAGP ingredients are dissolved in ammonia water. Then, the solution in which all the raw materials are dissolved is heat-treated to crystallize LAGP.

  Next, in order to produce LAGP having excellent properties while using the above-described basic LAGP production method, first, the solubility of each raw material in ammonia water was examined. As a result, all the raw materials were dissolved in ammonia water with an ammonia concentration of 0.2 mol / L (hereinafter, M). Therefore, next, ammonia water having an ammonia concentration higher than 0.2 M was prepared, and each material was tried to be dissolved in each of ammonia water having different concentrations.

  The following Table 1 shows the solubility of the raw material of LAGP in aqueous ammonia.

表１に示したように、各原料を、アンモニア濃度が０Ｍの水と、アンモニア濃度が０．２５５Ｍ〜７．２Ｍのアンモニア水に溶解させてみた。そして水に溶解しなかったのはＧｅＯ_２のみであり、他の化合物は水に溶解した。また、ＧｅＯ_２と酢酸リチウムは、７．２Ｍの高濃度のアンモニア水まで溶解し、硝酸アルミニウムは、１．３５Ｍの濃度のアンモニア水に溶解し、それよりも高い濃度のアンモニア水には溶解しなかった。またリン酸二水素アンモニウムは、１．８Ｍよりも濃度が高いアンモニア水には溶解しなかった。以上の溶媒に対する溶解性の検討結果より、上記原料を用いて溶液法でＬＡＧＰを作製するためには、ＧｅＯ_２を水に混合した後、その水に高濃度のアンモニア水を加えるなどして、アンモニア濃度が０．２Ｍ以上１．３５Ｍ以下に調整されたアンモニア水にＧｅＯ_２以外の原料を混合して溶解させることになる。そして、全ての原料を溶解させた溶液を熱処理することでＬＡＧＰを作製することになる。

As shown in Table 1, each raw material was dissolved in water having an ammonia concentration of 0 M and ammonia water having an ammonia concentration of 0.255 M to 7.2 M. And only GeO ₂ did not dissolve in water, and the other compounds were dissolved in water. In addition, GeO ₂ and lithium acetate dissolve up to a high concentration of aqueous ammonia of 7.2 M, aluminum nitrate dissolves in aqueous ammonia at a concentration of 1.35 M, and dissolves in aqueous ammonia at a higher concentration than that It was not. In addition, ammonium dihydrogen phosphate was not dissolved in ammonia water having a concentration higher than 1.8 M. From the results of the above solubility study in solvents, in order to produce LAGP by the solution method using the above-mentioned raw materials, after mixing GeO ₂ with water, adding high concentration ammonia water to the water, etc. A raw material other than GeO ₂ is mixed and dissolved in ammonia water adjusted to an ammonia concentration of 0.2 M or more and 1.35 M or less. Then, the solution in which all the raw materials are dissolved is heat treated to produce LAGP.

=== First Example ===
Next, as a method for producing a solid electrolyte according to the first embodiment of the present invention, a procedure for producing LAGP from a raw material of LAGP dissolved in a solvent containing ammonia will be mentioned. FIG. 1 shows the procedure of the method of manufacturing a solid electrolyte according to the first embodiment. A container containing water as a solvent is prepared (s1), and GeO ₂ is mixed with the water (s2). Note that GeO ₂ does not dissolve in water as a solvent in this step (hereinafter, also referred to as a first mixing step). Next, ammonia is added to the mixed solution of GeO ₂ and water, and the solvent is prepared to have a predetermined ammonia concentration (s 3). Here, the ammonia concentration of the solvent was prepared by adding 28 M high concentration ammonia water to water. GeO ₂ is dissolved by this ammonia concentration adjustment step (s3). The raw material of LAGP other than GeO ₂ is mixed with each ammonia aqueous solution of GeO _{2 with which} ammonia concentration differs (s4). In the figure, CH ₃ COOLi · 2H ₂ O, Al (NO ₃ ) ₃ · 9H ₂ O, and NH ₄ H ₂ PO ₄ are mixed in this order with an aqueous solution of GeO ₂ in ammonia, but GeO ₂ The order of mixing the raw materials other than each other may be back and forth with each other as long as it is after the ammonia concentration adjusting step (s3).

  If the step of mixing all the raw materials of LAGP into the first solution (hereinafter also referred to as the second mixing step (s4)) as described above is performed, the mixed solution is heat-treated to finally obtain the LAGP Transfer to the step of obtaining crystals. Here, first, a container is placed on a hot plate at a temperature of 100 ° C. and a solvent removing step (s5) is performed to evaporate the solvent while stirring the mixture, and then the material remaining in the container is subjected to an oven And the like at a temperature of 260 ° C. (s6). Further, the material in the container obtained by the drying step (s6) is heat-treated at a temperature of 450 ° C. for 2 hours in a nitrogen atmosphere (s7). This heat treatment (s7) is a step for obtaining amorphous LAGP, but here, this step (hereinafter referred to as “coating baking” is performed under the condition assuming that a film of LAGP is formed on the particle surface of the electrode active material Step (s7) is carried out. Finally, LAGP is crystallized in the firing step (s8).

By the way, in the method for producing a solid electrolyte according to the first embodiment, amorphous LAGP is attached to the particle surface of the powdery electrode active material in the coating and firing step (s7), and the firing step (s8) is performed thereon. ) Is supposed to crystallize LAGP. However, lithium vanadium phosphate (Li ₃ V ₂ (PO ₄ ) ₃ ), lithium cobalt phosphate (LiCoPO ₄ ) and titanium dioxide (TiO ₂ ), which are known as electrode active materials for all solid state batteries, are 700 ° C. It may react with LAGP at these temperatures. Therefore, when a film of LAGP is actually formed on the particle surface of the electrode active material, in the coating and firing step (s7), the electrode active material is heat treated at a temperature lower than the firing temperature to make LAGP amorphous. In the firing step (s8), it is necessary to crystallize LAGP at a temperature lower than 700.degree. And here, LAGP was crystallized on baking conditions of 625 degreeC and 2 hours by nitrogen atmosphere.

<Characteristics evaluation>
In order to evaluate the characteristics of LAGP produced by the method according to the first example, GeO ₂ was dissolved in various solvents having different ammonia concentrations in the ammonia concentration adjusting step (s3). And LAGP produced from the liquid mixture which mixes each solvent from which an ammonia concentration differs, and the raw material of LAGP was made into the sample. In addition to samples produced by the procedure using the solution method, LAGP produced using the solid phase method (hereinafter also referred to as a first reference example) as a sample serving as a reference in evaluating the characteristics of these samples Prepared.

The sample according to the first reference example can be produced, for example, by the following procedure. First, powders of Li ₂ CO ₃ , Al ₂ O ₃ , GeO ₂ and NH ₄ H ₂ PO ₄ , which are raw materials of LAGP, are weighed to have a predetermined composition ratio, mixed in a magnetic mortar or ball mill, and the mixture Is put into an alumina crucible or the like, and temporarily baked at a temperature of 300 ° C. to 400 ° C. for 3 hours to 5 hours. The calcined powder is dissolved by heat-treating the calcined powder obtained by calcination at a temperature of 1200 ° C. to 1400 ° C. for 1 h to 2 h. Then, the melted sample is quenched and vitrified to obtain a powder composed of amorphous LAGP. Next, the amorphous LAGP powder is pulverized using a pulverizing apparatus such as a ball mill and fired to crystallize LAGP. The firing conditions are the same as in the first embodiment.

  The crystal structure of some of the various samples prepared as described above was examined using an X-ray diffractometer (XRD). The XRD measurement result of the sample is shown in FIG. As shown in FIG. 2, it was confirmed that crystals of LAGP were formed in all the samples for which the XRD measurement was performed. And in the sample whose ammonia concentration of a solvent is 0.225M-1.35M, generation | occurrence | production of a heterophase was not confirmed similarly to the sample concerning a 1st reference example. However, in the samples with ammonia concentrations of 1.8 M and 3.6 M, different phases other than LAGP were formed. This is considered to be attributable to the presence of the raw material which did not dissolve in the solvent.

Next, the ion conductivity of the produced sample was measured. In the measurement of the ion conductivity, for example, LAGP in powder form obtained by the coating baking process before baking is press-formed at a pressure of 200 kgf / cm ² so as to be a pellet of φ 20 mm, and the pellet is baked As an electrode, Au was formed into a film with a thickness of 0.1 μm on both sides of the disk-like sintered body obtained as a sample, and this was used as a sample for measurement of ion conductivity. The impedance of the sample was then measured to determine the ion conductivity.

The ion conductivity σ (S / cm ² ) of each sample is shown in FIG. Here, a graph is shown in which the concentration of ammonia is taken on the horizontal axis and the ion conductivity σ is taken on the vertical axis. The vertical axis is on a logarithmic scale. As shown in FIG. 3, in the sample prepared by dissolving the raw material in a solvent having an ammonia concentration of 0.5 M or more, it is confirmed that the ammonia concentration and the ion conductivity have a proportional relationship in which the slope is almost negative. did it. That is, the ion conductivity σ decreased as the ammonia concentration increased. And if it is 1.35 M or less, practicable ion conductivity (sigma) more than 1 * 10 < ^-6 > (S / cm < ² >) was obtained. In the sample with an ammonia concentration of less than 0.5 M, an ion conductivity σ equal to or higher than 1 × 10 ⁻⁶ (S / cm ² ) is obtained, but the ammonia concentration and the ion conductivity σ The relationship was out of proportion to the above. In addition, variations were observed in the ionic conductivity σ between samples having the same ammonia concentration. This is presumably because GeO ₂ was not completely dissolved in the solvent when the ammonia concentration of the solvent was low, and there were individual differences in the crystal structure of LAGP between samples.

The sample according to the first reference example prepared by the solid phase method exhibited an ion conductivity σ of 1 × 10 ⁻⁵ (S / cm ² ) or more. And also about LAGP produced by the method which concerns on 1st Example, if the ammonia concentration of a solvent is adjusted appropriately, ionic conductivity (sigma) near 1 * 10 < ^-5 > (S / cm < ² >) was obtained. In the case of the raw material used in the first example, the highest ion conductivity σ was obtained at an ammonia concentration of 0.45 M. As described above, according to the method for producing a solid electrolyte according to the first embodiment, LAGP having a small number of different phases and having practical ion conductivity σ can be produced using a solution method. Therefore, LAGP can be provided at lower cost.

=== Second Example ===
In the method of manufacturing a solid electrolyte according to the first embodiment, LAGP is manufactured using a solution method. By applying the method for producing a solid electrolyte according to the first embodiment, it is possible to mix the powdered electrode active material with the liquid LAGP raw material, and to coat the LAGP film on the particle surface of the electrode active material. It becomes possible to form effectively. However, depending on the time of mixing the electrode active material in the process of producing LAGP by the method of the first embodiment, the mixing condition of the electrode active material, or the condition of heat treatment after mixing the electrode active material, etc. There is also a possibility that an electrode material having various characteristics can not be obtained. Therefore, as a second embodiment of the present invention, a method of manufacturing an electrode material for effectively forming a film of LAGP on the particle surface of the electrode active material will be described by applying the first embodiment. In the second embodiment, TiO ₂ was used as the electrode active material. In addition, in order to evaluate the characteristics of the electrode material manufactured according to the second embodiment, various electrode materials different in the time of mixing the electrode active material and the temperature of heat treatment in the baking process are manufactured as samples in the process of forming LAGP. did.

  Table 2 below shows the preparation conditions of each sample.

図４と図５に各サンプルの作製手順を示した。図４は、表２におけるサンプル１〜３の作製手順を示しており、図１に示した第１の実施例に係るＬＡＧＰの製造手順に対し、アンモニア濃度調整工程（ｓ３）と第２混合工程（ｓ４）との間に電極活物質を混合する電極活物質の混合工程（ｓ１０）が挿入されている。そして、サンプル１、２、および３では、焼成工程（ｓ８）における焼成温度を、４２５℃、６２５℃、および８００℃としている。なお、焼成工程（ｓ８）における焼成温度以外の条件については、第１の実施例と同様であり、窒素雰囲気中で２時間掛けて焼成している。なお、第１混合工程、第２混合工程、および活物質混合工程（ｓ１０）では、焼成工程（ｓ９）によって得られる電極材料中のＬＡＧＰとＴｉＯ_２との質量比が７０ｗｔ％と３０ｗｔ％となるようにＬＡＧＰの原料およびＴｉＯ_２を混合している。また、アンモニア濃度調整工程（ｓ３）では、溶媒のアンモニア濃度を０．４５Ｍに調整している。

The preparation procedure of each sample is shown in FIG. 4 and FIG. FIG. 4 shows the preparation procedure of Samples 1 to 3 in Table 2, and the ammonia concentration adjusting step (s3) and the second mixing step are different from the preparation procedure of LAGP according to the first example shown in FIG. The mixing step (s10) of the electrode active material for mixing the electrode active material with (s4) is inserted. And, in Samples 1, 2 and 3, the firing temperature in the firing step (s8) is set to 425 ° C., 625 ° C. and 800 ° C. The conditions other than the firing temperature in the firing step (s8) are the same as in the first embodiment, and firing is performed in a nitrogen atmosphere for 2 hours. In the first mixing step, the second mixing step, and the active material mixing step (s10), the mass ratio of LAGP to TiO ₂ in the electrode material obtained in the firing step (s9) is 70 wt% and 30 wt%. As a raw material of LAGP and TiO ₂ are mixed. In the ammonia concentration adjusting step (s3), the ammonia concentration of the solvent is adjusted to 0.45M.

FIG. 5 shows the preparation procedure of the sample 4 in Table 2, and this procedure corresponds to the method of manufacturing the electrode material according to the second embodiment. In the procedure shown in FIG. 5, the active material mixing step (s10) is inserted between the second mixing step (s4) and the solvent removing step (s5) in the production procedure of LAGP according to the first embodiment. ing. Further, also in the preparation procedure of sample 4 shown in FIG. 5, in the first mixing step, the second mixing step, and the active material mixing step (s10), the mass ratio of LAGP to TiO ₂ in the baking step (s9) is The raw material of LAGP and TiO ₂ are mixed so as to be 70 wt% and 30 wt%, and in the ammonia concentration adjusting step (s3), the ammonia concentration of the solvent is adjusted to 0.45M.

Next, in order to evaluate the characteristics of the samples 1 to 4 manufactured according to the above-described procedure, a powder material (hereinafter also referred to as a second reference example) having characteristics to be the reference of the evaluation was manufactured. The powder material according to the second reference example includes powdery LAGP prepared by the solid phase method as the first reference example, and powdery TiO ₂ after heat treatment under the same conditions as the firing temperature of LAGP. And 70% by weight and 30% by weight.

In FIG. 6, the XRD measurement result of the powder material which concerns on the samples 1-3 and a 2nd reference example was shown. First, from the XRD measurement results of the second reference example, the peak position (2θ) of the X-ray diffraction intensity of each of LAGP produced by the solid phase method and TiO ₂ of simple substance is specified, and corresponds to that LAGP and TiO ₂ looking at the peak position (2 [Theta]) in the sample 1-4 and the position of the peak (2 [Theta]) with reference to, but the peak of the sample 1 in TiO ₂ were the firing temperature and 425 ° C. can be confirmed, a peak corresponding to the LAGP It was also confirmed that LAGP did not crystallize at this firing temperature. In addition, a peak corresponding to the heterophase GeO ₂ was also confirmed.

In Samples 2 and 3 with a firing temperature of 625 ° C., the peak of TiO ₂ can be confirmed, and the peak of LAGP can also be confirmed at the position of the X-ray diffraction angle (2θ) indicated by α in the figure. I found that In sample 2, the peak corresponding to GeO ₂ can also be confirmed. Further, in the sample 3 the firing temperature was 800 ° C. higher than 700 ° C., instead peak of _{LAGP, Li 1.4 (Al 0.4 Ge} 0 that may have formed by the reaction of LAGP and TiO _{2. The} crystal phase corresponding to ₂ Ti _1.4 ) (PO ₄ ) ₃ was confirmed.

Next, XRD measurement was performed on Sample 4 which had the same firing conditions as Sample 2 but different timings of mixing TiO _{2 in} the production process of LAGP. FIG. 7 is a view showing the XRD measurement results of sample 2, sample 4 and the second reference example, and FIG. 7 (A) shows the XRD measurement results for all the measured X-ray diffraction angle ranges. 7 (B) is an enlarged view of the XRD measurement result of the angle range indicated by symbol .delta.1 in FIG. 7 (A), and FIG. 7 (C) is a rectangular frame in FIG. 7 (B). It is the figure which expanded area | region (delta) 2 shown.

Then, as shown in FIG. 7 (A), the sample 4, the peak of GeO ₂ which have appeared in the sample 2 was not found. Further, as shown in FIG. 7B, in the sample 4 relative to the sample 2, the peak of TiO ₂ is sharper. This is considered to be due to the fact that the pH of the solvent at the time of execution of the active material mixing step (s10) was different between sample 2 and sample 4. Therefore, when the pH value of the solvent was measured before and after the second mixing step (s4) in the preparation procedure of LAGP shown in FIG. 1, the pH value is 11.3 before the second mixing step (s4). In contrast, after the second mixing step (s4), the pH value was 10.3. That is, in the method of manufacturing the electrode material according to the second embodiment shown in FIG. 5, the electrode active material is mixed in a solvent having a low pH. And in the sample 4 manufactured by the manufacturing method of the electrode material according to the second embodiment, the characteristic deterioration due to the reaction between the electrode active material and the alkaline solution is suppressed, so the peak of TiO ₂ is steeper than that of the sample It is thought that it became. Furthermore, as shown in FIG. 7C, in sample 4, a very small peak of GeO ₂ in sample 2 was not confirmed. As described above, according to the method of manufacturing the electrode material according to the second embodiment, it is possible to form a highly pure LAGP film on the particle surface of the electrode active material.

=== Manufacturing method of all solid state battery ===
The all-solid battery is produced by producing a laminate in which a sheet-like positive electrode material, a solid electrolyte, and a negative electrode material are laminated in this order by the above-described compression molding method or green sheet method, and firing is performed on the laminate. It is made. And in the all-solid-state battery using LAGP as a solid electrolyte, amorphous LAGP will be crystallized by the process of baking a laminated body. That is, the firing step (s8) in FIGS. 1, 4 and 5 is a step assuming firing of the laminate, and relates to the method of manufacturing a solid electrolyte and the second embodiment in the first embodiment. In the case of producing an all-solid battery using the method for producing an electrode material, a sheet-like positive electrode material, a solid electrolyte, and a negative electrode material are laminated in this order between the coating firing step (s7) and the firing step (s8) A procedure for making a laminate will be inserted. Moreover, in FIG. 4, FIG. 5, the powder material produced by the coating baking process (s7) turns into an electrode material.

=== Other Examples ===
In the second embodiment, the coating of LAGP can be effectively formed on the particle surface of the electrode active material by applying the solid electrolyte manufacturing method according to the first embodiment. However, the method for producing a solid electrolyte according to the first embodiment is not limited to the use of forming a film on an electrode active material. According to the method for producing a solid electrolyte according to the first embodiment, since LAGP having practical characteristics can be produced by a very simple procedure using a solution method, the LAGP can be used as a solid electrolyte layer of an all solid battery. You may use. This makes it possible to provide an all solid battery at a lower cost.

Among the raw materials of LAGP, the raw materials comprising water-soluble compounds other than GeO ₂ are not limited to those used in the first and second examples. And, if the raw materials are different, naturally the concentration of ammonia which is soluble in the solvent is different. In any case, it is sufficient that the concentration of ammonia in which the solvent dissolves all the raw materials of LAGP including GeO ₂ is adjusted by the ammonia concentration adjusting step.

In the first and second embodiments, a film of LAGP is formed on an electrode active material which may react with LAGP when it is fired at a temperature of 700 ° C. or more, such as LVP, LCPO, TiO ₂ or the like. Was assumed. Of course, the electrode active material is not limited to these compounds. And, as for other electrode active materials, there may be those which can be heat-treated together with LAGP at higher temperatures. However, LVP, LCPO, TiO _{2 and the} like assumed in each of the above examples are known as electrode active materials for all solid batteries, and in order to put the all solid batteries into practical use at an early stage, It can be said that it is realistic to use an electrode active material. Therefore, in the example of the present invention, the upper limit of the firing temperature is set to 625 ° C., which is 75 ° C. lower than 700 ° C. In each of the above-described examples, crystallized LAGP could be obtained even at the sintering temperature of 625 ° C.

In the method of manufacturing the electrode material according to the second embodiment, TiO ₂ which is a negative electrode active material is used as the electrode active material. Of course, the method of manufacturing the electrode material according to the second embodiment is the electrode The active material can be applied to the electrode material for the positive electrode only by using the positive electrode active material. In addition, when producing an all-solid-state battery, the electrode material of both the positive electrode layer and the negative electrode layer may be produced by the method of producing an electrode material according to the second embodiment, or either positive or negative electrode material May be produced.

  s2 first mixing step, s3 ammonia concentration adjusting step, s4 second mixing step, s7 coating baking step, s8 baking step

Claims (4)

A method of producing a solid electrolyte represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ , wherein 0 <x ≦ 1.
Using GeO ₂ and several water soluble compounds as raw materials,
Mixing the GeO ₂ in water with a first mixing step;
Ammonia concentration adjusting step of adding ammonia to the mixed solution obtained in the first mixing step to dissolve the GeO ₂ in the solution to obtain a first solution and adjusting the ammonia concentration of the first solution; ,
A second mixing step of mixing the plurality of water-soluble compounds into the first solution to obtain a second solution;
Heat treating the second solution to obtain an amorphous solid electrolyte;
Firing the amorphous solid electrolyte to crystallize LAGP;
Including
In the ammonia concentration adjusting step, the ammonia concentration of the first solution is adjusted to a concentration at which all the water soluble compounds are dissolved.
A method of producing a solid electrolyte characterized in that In the method for producing a solid electrolyte according to claim 1,
The plurality of water-soluble compounds are CH ₃ COOLi · 2H ₂ O, Al (NO ₃ ) ₃ · 9H ₂ O, NH ₄ H ₂ PO ₄ ,
In the ammonia concentration adjusting step, the ammonia concentration of the first solution is adjusted to 0.2 M or more and 1.35 M or less.
A method of producing a solid electrolyte characterized in that Production of electrode material in which solid electrolyte represented by general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ is coated as 0 <x ≦ 1 on particle surface of electrode active material for all solid battery Method,
Using GeO ₂ and a plurality of water-soluble compounds as the material of the solid electrolyte,
Mixing the GeO ₂ in water with a first mixing step;
Ammonia concentration adjusting step of adding ammonia to the mixed solution obtained in the first mixing step to dissolve the GeO ₂ in the solution to obtain a first solution and adjusting the ammonia concentration of the first solution; ,
A second mixing step of mixing the plurality of water-soluble compounds into the first solution to obtain a second solution;
An active material mixing step of mixing the powdered electrode active material with the second solution;
Heat treatment at a temperature lower than a calcination temperature at which the solid electrolyte crystallizes, the mixture liquid obtained in the active material mixing step to obtain an amorphous solid electrolyte;
Including
In the ammonia concentration adjusting step, the ammonia concentration of the first solution is adjusted to a concentration at which all the water soluble compounds are dissolved.
The manufacturing method of the electrode material for all the solid batteries characterized by the above-mentioned. In an integral sintered body, a positive electrode layer including a positive electrode active material and a solid electrolyte, a solid electrolyte layer including a solid electrolyte, and a negative electrode layer including a negative electrode active material and a solid electrolyte are laminated in this order. It is a manufacturing method of the all-solid-state battery provided with the following lamination electrode body,
A positive electrode material in which the solid electrolyte in an amorphous state and the electrode active material for the positive electrode are mixed by using the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ as the solid electrolyte, where 0 <x ≦ 1. And an electrode material preparation step of preparing a negative electrode material in which the solid electrolyte in an amorphous state and an electrode active material for the negative electrode are mixed.
A firing step of producing the laminated electrode body by firing a laminated body formed by sandwiching a layered solid electrolyte material containing the solid electrolyte between the layered positive electrode material and the layered negative electrode material;
Including
In the electrode material preparation step,
A solid electrolyte preparation step of preparing a solid electrolyte using GeO ₂ and a plurality of water soluble compounds as a raw material by a solution method;
An active material mixing step of mixing a powdered electrode active material with the raw material in the process of manufacturing the solid electrolyte by the solid electrolyte manufacturing step;
Run
In the solid electrolyte preparation step,
Mixing the GeO ₂ in water with a first mixing step;
Ammonia concentration adjusting step of adding ammonia to the mixed solution obtained in the first mixing step to dissolve the GeO ₂ in the solution to obtain a first solution and adjusting the ammonia concentration of the first solution; ,
A second mixing step of mixing the plurality of water-soluble compounds into the first solution to obtain a second solution;
Heat treating the second solution at a temperature lower than a calcination temperature at which the solid electrolyte crystallizes to obtain an amorphous solid electrolyte;
Including
In the ammonia concentration adjusting step, the ammonia concentration of the first solution is adjusted to a concentration at which all the water-soluble compounds dissolve.
Performing the active material mixing step between the second mixing step and the vitrification step;
A method of manufacturing an all solid battery characterized in that

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