JP5838954B2 - Method for producing sulfide solid electrolyte - Google Patents

Description

  The present invention relates to a method for producing a sulfide solid electrolyte.

  Lithium ion secondary batteries have a higher energy density than conventional secondary batteries and can be operated at a high voltage. For this reason, it is used as a secondary battery that can be easily reduced in size and weight in information equipment such as a mobile phone, and in recent years, there is an increasing demand for large motive power such as for electric vehicles and hybrid vehicles.

  A lithium ion secondary battery has a positive electrode layer and a negative electrode layer, and an electrolyte layer disposed between them. Examples of the electrolyte used for the electrolyte layer include non-aqueous liquid and solid substances. Are known. When a liquid electrolyte (hereinafter referred to as “electrolytic solution”) is used, the electrolytic solution easily penetrates into the positive electrode layer and the negative electrode layer. Therefore, an interface between the active material contained in the positive electrode layer or the negative electrode layer and the electrolytic solution is easily formed, and the performance is easily improved. However, since the widely used electrolyte is flammable, it is necessary to mount a system for ensuring safety. On the other hand, when a solid electrolyte that is flame retardant (hereinafter referred to as “solid electrolyte”) is used, the above system can be simplified. Therefore, development of a lithium ion secondary battery (hereinafter, sometimes referred to as “all-solid battery”) in a form provided with a layer containing a solid electrolyte (hereinafter referred to as “solid electrolyte layer”) proceeds. It has been.

As a technology related to such a lithium ion secondary battery, for example, Patent Document 1 discloses an amorphous material synthesized by amorphizing a raw material composition containing Li ₂ S, P ₂ S ₅ , and LiI. A method for producing a sulfide solid electrolyte material is disclosed in which a sulfide solid electrolyte material is heat-treated at a temperature equal to or higher than a crystallization temperature to obtain a sulfide solid electrolyte material that is glass ceramics. The specification of Patent Document 1 discloses that wet mechanical milling is preferably used when an amorphous sulfide solid electrolyte material is synthesized. Patent Document 2 discloses a method for producing a sulfide solid electrolyte material having an atomization step of adding an ether compound to a coarse particle material of a sulfide solid electrolyte material and atomizing the coarse particle material by a pulverization process. ing. In addition, in the specification of Patent Document 2, it is disclosed that the I-containing compound may be contained in the coarse-grained material. In addition, after the atomization step, the atomized material is brought to a temperature equal to or higher than the crystallization temperature. It is disclosed that a heat treatment step of heating at a temperature may be included. Patent Document 3 discloses that ethers may be added to a hydrocarbon-based solvent when producing a sulfide solid electrolyte via wet mechanical milling using a hydrocarbon-based solvent. In addition, it is disclosed that the amount of the raw material (total amount) added to 1 kg of the solvent is particularly preferably 0.1 to 0.3 kg. Patent Document 4 discloses that wet mechanical milling using a liquid containing ethers may be performed when producing a sulfide solid electrolyte material containing at least one of Cl and Br. Further, it is disclosed that a crystalline sulfide solid electrolyte material may be obtained by heat-treating the synthesized sulfide solid electrolyte material.

JP 2012-104279 A Japanese Patent Application No. 2011-155189 JP 2010-250981 A JP 2012-48971 A

  The sulfide solid electrolyte containing halogen can enhance ion conduction performance by crystallization. Further, by using a sulfide solid electrolyte having a reduced particle size (fine particles), it becomes possible to reduce the reaction resistance of the all-solid battery. Therefore, it is considered that the performance of the all-solid battery can be improved by using the crystallized particulate solid electrolyte. According to the technique disclosed in Patent Document 1, a crystallized sulfide solid electrolyte can be obtained. However, when the crystallized sulfide solid electrolyte is made into fine particles, there is a problem in that the crystal structure that enhances ion conduction performance is broken and vitrified, resulting in a significant decrease in ion conduction performance. Such a problem is difficult to solve by simply combining the technique disclosed in Patent Document 1 and the techniques disclosed in Patent Document 3 and Patent Document 4.

  Then, this invention makes it a subject to provide the manufacturing method of the sulfide solid electrolyte which can manufacture the particulate sulfide solid electrolyte which improved the ion conduction performance.

  As a result of intensive studies, the inventors have made it possible to produce a particulate sulfide solid electrolyte with improved ion conduction performance by making the sulfide solid electrolyte into fine particles and then heating and crystallizing. I found out that Furthermore, as a result of intensive studies, the inventors have made fine particles whose ion conduction performance has been improved by making the concentration of the sulfide solid electrolyte within a predetermined range when atomized by wet mechanical milling before crystallization. It has been found that it is easier to produce a solid sulfide solid electrolyte. The present invention has been completed based on these findings.

In order to solve the above problems, the present invention takes the following means. That is,
The present invention provides a synthesis step for synthesizing a coarse raw material of a sulfide solid electrolyte containing halogen, and a volume-based particle size obtained by measuring the synthesized coarse raw material with a particle size distribution measuring device based on a laser diffraction / scattering method. In the distribution, a micronization step for micronizing until the median diameter D ₅₀ corresponding to 50% by volume cumulative from the microparticles side becomes 5 μm or less, and a crystallization step for crystallizing the micronized sulfide solid electrolyte A method for producing a sulfide solid electrolyte.

  By heating and crystallizing the finely divided sulfide solid electrolyte, it is possible to produce a finely divided sulfide solid electrolyte having high ion conductivity. Therefore, according to this invention, the manufacturing method of the sulfide solid electrolyte which can manufacture the particulate sulfide solid electrolyte which improved the ion conduction performance can be provided.

Further, in the present invention, the micronization step is a step of micronizing by a wet media type pulverization treatment, and the total amount of the solvent, additive, and coarse raw material used in the wet media type pulverization treatment is occupied. The mass ratio X of the granule raw material is preferably 0.1 ≦ X ≦ 0.35.
Here, the media refers to, for example, a ball mill. By controlling X to 0.1 ≦ X ≦ 0.35 by wet pulverization, it becomes easy to produce a particulate sulfide solid electrolyte with improved ion conduction performance.

Further, the micronization step is a step of micronization by a wet media type pulverization process, and the mass of the coarse raw material in the total mass of the solvent, additive, and coarse raw material used in the wet media type pulverization process In the present invention in which the ratio X is 0.1 ≦ X ≦ 0.35, the micronization step is a step in which a planetary ball mill is used, and coarse particles defined by the following formula (1) The total pulverization energy E per unit weight of the raw material is preferably in the range of 400 kJ · sec / g to 2000 kJ · sec / g. A finely divided sulfide solid electrolyte having improved ion conduction performance by setting the total pulverization energy E per unit weight of the coarse-grain raw material in the wet pulverization treatment to 400 kJ · sec / g or more and 2000 kJ · sec / g or less. Easy to manufacture.
E = 1/2 nmv ² / s · t Equation (1)
(N is the number of media (pieces), m is the weight (kg) per media, v is the speed of the media (m / s), s is the amount of coarse raw material (g), and t is the processing time (seconds) ).)

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the sulfide solid electrolyte which can manufacture the particulate sulfide solid electrolyte which improved the ion conduction performance can be provided.

It is a flowchart explaining the manufacturing method of sulfide solid electrolyte. It is a figure explaining an all-solid-state battery. It is a figure which shows a powder X-ray-diffraction measurement result. It is a figure explaining the measurement result of lithium ion conductivity. It is a figure explaining the measurement result of lithium ion conductivity.

  The present invention will be described below with reference to the drawings. In addition, the form shown below is an illustration of this invention and this invention is not limited to the form shown below.

  FIG. 1 is a diagram for explaining a method for producing a sulfide solid electrolyte of the present invention (hereinafter referred to as “the production method of the present invention”). The manufacturing method of the present invention shown in FIG. 1 includes a synthesis step (S1), a fine particle formation step (S2), and a crystallization step (S3).

The synthesis step (hereinafter, sometimes referred to as “S1”) is a step of synthesizing a coarse-grain raw material of a sulfide solid electrolyte containing halogen (hereinafter, sometimes simply referred to as “coarse-grain raw material”). . The form of S1 is not particularly limited as long as it can synthesize a coarse raw material (a material before being microparticulated in the micronization step described later), and the coarse raw material is synthesized by a known method such as wet mechanical milling. And a process of performing. Examples of the halogen that can be contained in the coarse raw material synthesized in S1 include F, Cl, Br, and I. S1 is, for example, Li ₂ S, a sulfide of A (A is at least one selected from the group consisting of P, Si, Ge, Al, and B), and a halogen-containing compound (F-containing compound). And at least one selected from the group consisting of a Cl-containing compound, a Br-containing compound, and an I-containing compound)). it can. Among these, from the viewpoint of making it easy to obtain a sulfide solid electrolyte with improved ion conduction performance, using a raw material composition containing an I-containing compound, a sulfide solid electrolyte containing I (for example, in terms of moles) _{xLiI · (100-x) 0.75Li} 2 S · 0.25P 2 S 5 (10 ≦ x ≦ 30)) a step of synthesizing a coarse raw materials, it is preferable to.

  In the case of synthesizing a coarse raw material in S1 by wet mechanical milling, for example, a ball having a diameter of 1 mm or more and 10 mm or less can be used, and the wet mechanical milling time can be set, for example, by 10 hours or more and 100 hours or less. As the solvent, for example, a hydrocarbon solvent can be used. Examples of hydrocarbon solvents that can be used in S1 include hexane, heptane, octane, nonane, decane, aromatic hydrocarbons such as benzene, toluene, and xylene, and cyclic hydrocarbons such as cyclohexane. .

  Further, when the coarse raw material is synthesized in S1 by wet mechanical milling, the drying conditions after the synthesis are set to be equal to or higher than the volatile temperature of the solvent and lower than the crystallization temperature of the coarse raw material. The crystallization temperature varies depending on the composition of the raw material, but is, for example, in the range of 130 ° C. or higher and 250 ° C. or lower, preferably in the range of 160 ° C. or higher and 220 ° C. or lower, and more preferably in the range of 170 ° C. or higher and 200 ° C. or lower. The drying time after synthesis can be, for example, 10 minutes to 24 hours. When drying coarse raw materials, a hot plate, a drying furnace, an electric furnace, or the like can be used as appropriate.

  The micronization step (hereinafter sometimes referred to as “S2”) is a step of micronizing the coarse raw material synthesized in S1. The form of S2 is not particularly limited as long as the coarse raw material can be made into fine particles, and can be a step of making the coarse raw material into fine particles by a known method. In S2, for example, in addition to media-type pulverization such as a bead mill and a ball mill, coarse raw materials can be made into fine particles by jet pulverization or cavitation pulverization. The conditions for pulverization (pulverization conditions) are set so that the coarse raw material can be pulverized to a desired particle diameter. For example, when a planetary ball mill is used, a coarse raw material, a solvent, an additive, and a grinding ball are added, and the grinding process is performed at a predetermined rotation speed and time. When a planetary ball mill is used, the ball diameter (φ) of the grinding balls in S2 is not particularly limited. From the viewpoint of facilitating handling of the grinding balls, the ball diameter of the grinding balls can be 0.05 mm or more, preferably 0.1 mm or more. The material of the ball for grinding is not particularly limited as long as a sulfide solid electrolyte with few impurities can be obtained. For example, it can be made of zirconia or alumina. Further, from the viewpoint of making the coarse raw material easy to grind into a desired particle diameter, the ball diameter of the grinding balls can be 5 mm or less, and preferably 1 mm or less. Further, the rotation speed of the base plate when performing the planetary ball mill is, for example, preferably 100 to 400 revolutions per minute, and more preferably 150 to 300 revolutions per minute. Moreover, the processing time at the time of performing a planetary ball mill can be 1 hour or more and 100 hours or less, for example.

In the production method of the present invention, S2 is preferably a wet media-type pulverization treatment from the viewpoint of easily obtaining a particulate sulfide solid electrolyte. The total pulverization energy E per unit weight of the coarse raw material in the wet media type pulverization treatment defined by the following formula (1) is preferably 50 kJ · sec / g or more and 4000 kJ · sec / g or less. 400 kJ · sec / g to 2000 kJ · sec / g, more preferably 450 kJ · sec / g to 2000 kJ · sec / g.
E = 1/2 nmv ² / s · t Equation (1)
In the formula (1), n is the number of media (pieces), m is the weight (kg) per media, v is the speed of the media (m / s), s is the amount of coarse raw material (g), t Is the processing time (seconds). Formula (1) shows the total pulverization energy when it is assumed that the kinetic energy of the media (for example, beads and balls) is all used for pulverization of the coarse raw material.
The media speed v can be determined as appropriate according to the type of media-type grinding process. For example, in the case of a planetary ball mill, the media speed v can be obtained by the following equation (2).
v = dπRα / 1000/60 (2)
In formula (2), d is the diameter (mm) of the pot (container), R is the number of rotations of the base plate (rpm), and α is the revolution ratio.

  On the other hand, when the pulverization treatment is cavitation pulverization, the number of rotations is preferably set to 1000 to 3000 rotations per minute, for example. Moreover, it is preferable that a flow rate shall be 1.0 g / min or more and 3.0 g / min or less, for example.

  Furthermore, in the production method of the present invention, from the viewpoint of making the ionic conductivity of the particulate sulfide solid electrolyte easy to increase, the solvent, additive, and coarse raw material used in the wet media type pulverization treatment are used. It is preferable that the ratio X of the mass of the coarse raw material in the total mass is 0.1 ≦ X ≦ 0.35. When S2 is a wet media type pulverization treatment, a solvent similar to the solvent that can be used in S1 can be used in S2, and an additive (for example, an ether compound, an ester compound, a nitrile compound) is added to the container containing the solvent. And the like, which can prevent adhesion and granulation of coarse raw materials, etc.), and after adding the coarse raw materials and media synthesized in S1, can be subjected to wet media type pulverization treatment. Moreover, in order to make it easy to suppress the generation of hydrogen sulfide (deterioration of the sulfide solid electrolyte material), the solvent preferably has a small amount of water.

  In S2, when an ether compound is used as an additive, the ether compound only needs to have an ether group (C—O—C), and from the viewpoint of making an ether compound having low reactivity with the coarse raw material, oxygen. It is preferred to have two hydrocarbon groups attached to the atom. Further, from the viewpoint of facilitating removal of the ether compound by drying, it is preferable that the number of carbon atoms of the hydrocarbon group bonded to the oxygen atom is 10 or less.

  The hydrocarbon group may be chain-like or cyclic. The hydrocarbon group is preferably a saturated hydrocarbon group or an aromatic hydrocarbon group. Examples of the hydrocarbon group include an alkyl group such as a methyl group, an ethyl group, a propyl group, an isopropyl group, and a butyl group, a cycloalkyl group such as a cyclopentyl group and a cyclohexyl group, and an aromatic hydrocarbon group such as a phenyl group and a benzyl group. Can be mentioned. Specific examples of the ether compound include dimethyl ether, methyl ethyl ether, dipropyl ether, dibutyl ether, cyclopentyl methyl ether, anisole and the like. The molecular weight of the ether compound is preferably 46 or more and 278 or less, and more preferably 74 or more and 186 or less.

  Further, the amount of the ether compound added is not particularly limited as long as it is a ratio at which a particulate sulfide solid electrolyte is obtained. From the viewpoint of making it easy to prevent the coarse raw material from adhering to the media during pulverization, the addition amount of the ether compound is preferably 0.01% by weight or more with respect to the coarse raw material, It is more preferably 0.1% by weight or more, and further preferably 1% by weight or more. Further, from the viewpoint of making the ether compound easy to remove after pulverization, the addition amount of the ether compound is preferably 100% by weight or less, for example, 50% by weight or less with respect to the coarse raw material. Is more preferable.

  Moreover, in S2, when using an ester compound as an additive, the ester compound should just have an ester group (-COO-). Further, from the viewpoint of facilitating removal of the ester compound by drying, the hydrocarbon group bonded to the oxygen atom preferably has 10 or less carbon atoms. As such a hydrocarbon group, the hydrocarbon group similar to the hydrocarbon group illustrated by description regarding an ether compound can be illustrated. Specific examples of the ester compound that can be used in S2 include ethyl acetate, butyl acetate, ethyl propionate, ethyl butyrate, butyl butyrate, and ethyl benzoate.

  The amount of the ester compound added is not particularly limited as long as it is a ratio at which a particulate sulfide solid electrolyte can be obtained. From the viewpoint of making it easy to prevent the coarse raw material from adhering to the media during pulverization, the amount of the ester compound added is preferably 0.01% by weight or more with respect to the coarse raw material, It is more preferably 0.1% by weight or more, and further preferably 1% by weight or more. In addition, from the viewpoint of making the ester compound easy to remove after pulverization, the amount of the ester compound added is preferably, for example, 100% by weight or less, and 50% by weight or less, based on the coarse raw material Is more preferable.

  Moreover, in S2, when using a nitrile compound as an additive, the nitrile compound should just have a cyano group (-CN). Further, from the viewpoint of facilitating removal of the nitrile compound by drying, the hydrocarbon group bonded to the carbon atom of the cyano group preferably has 10 or less carbon atoms. As such a hydrocarbon group, the hydrocarbon group similar to the hydrocarbon group illustrated by description regarding an ether compound can be illustrated. Specific examples of nitrile compounds that can be used in S2 include n-butyronitrile, isopropyl nitrile, tertiary butyronitrile, acetonitrile, benzonitrile and the like.

  Moreover, the addition amount of a nitrile compound will not be specifically limited if it is a ratio in which a particulate sulfide solid electrolyte is obtained. From the viewpoint of making it easy to prevent the coarse raw material from adhering to the media during pulverization, the addition amount of the nitrile compound is preferably 0.01% by weight or more with respect to the coarse raw material, It is more preferably 0.1% by weight or more, and further preferably 1% by weight or more. Further, from the viewpoint of making the nitrile compound easy to remove after pulverization, the addition amount of the nitrile compound is preferably 100% by weight or less, for example, 50% by weight or less with respect to the coarse raw material. Is more preferable.

  In S2, since the additive is used when the coarse raw material is pulverized, the additive functions as a dispersant for the coarse raw material, and it is possible to prevent the coarse raw material from adhering and granulating. As a result, it is possible to obtain a particulate sulfide solid electrolyte with a high recovery rate. The recovery rate of the sulfide solid electrolyte is, for example, preferably 90% or more, and more preferably 95% or more. The recovery rate can be calculated by (recovered amount of particulate sulfide solid electrolyte) / (input amount of coarse raw material).

  In the crystallization step (hereinafter sometimes referred to as “S3”), the sulfide solid electrolyte finely divided in S2 is heated to a temperature equal to or higher than the crystallization temperature and held for a predetermined time, This is a crystallization process. The crystallization temperature (heating temperature) varies depending on the composition of the finely divided sulfide solid electrolyte. For example, it is 130 ° C. or higher and 250 ° C. or lower, preferably 160 ° C. or higher and 220 ° C. or lower, more preferably 170 ° C. or higher and 200 ° C. or lower. Within range. Further, the time for holding at the crystallization temperature is not particularly limited as long as it is a time for crystallization of the finely divided sulfide solid electrolyte, and for example, it can be 5 minutes or more and 5 hours or less. In addition, although description is abbreviate | omitted in FIG. 1, by drying the sulfide solid electrolyte micronized between S2 and S3 over predetermined time (for example, 10 minutes or more and 24 hours or less), Remove solvent and additives. When drying the finely divided sulfide solid electrolyte, a hot plate, a drying furnace, an electric furnace or the like can be used as appropriate. The drying performed between S2 and S3 can be performed under the same conditions as the drying after synthesizing the coarse raw material.

  In the production method of the present invention, the sulfide solid electrolyte finely divided in S2 is crystallized by heating in S3. By manufacturing in such a process, it becomes possible to manufacture a particulate sulfide solid electrolyte having a crystal structure that realizes high lithium ion conductivity. In addition, when crystallizing after crystallizing, the crystal structure that realizes high lithium ion conductivity is broken and vitrified at the time of micronization, so that lithium ion conductivity is greatly reduced.

  Further, when the micronization step in the production method of the present invention is a step of micronizing by a wet media type pulverization treatment, the total pulverization energy E per unit weight of the coarse raw material is 400 kJ · sec / g or more and 2000 kJ · By being below sec / g, it becomes easy to obtain a particulate sulfide solid electrolyte.

  Further, a sulfide solid electrolyte containing halogen is likely to change its physical properties when it is made into fine particles, and particularly, halogen is easily separated and crystallized. When halogen is separated and crystallized, it is difficult to obtain a desired crystal structure when crystallizing after micronization, and it may be difficult to improve lithium ion conduction performance. Also, if the concentration of the solid electrolyte is too high during wet pulverization, the solid electrolyte particles collide with each other and agglomerate, resulting in separation of the halogen. As a result, the material composition tends to deviate from the target composition. Cannot be obtained, it may be difficult to improve the lithium ion conduction performance. Therefore, in the present invention, in order to easily avoid such a situation, when the micronization step is a wet media type pulverization process, the coarse raw material occupies the total mass of the solvent, the additive, and the coarse raw material. The mass ratio X is set to 0.1 ≦ X ≦ 0.35. By controlling X within this range, it becomes easy to produce a particulate sulfide solid electrolyte with improved lithium ion conduction performance.

  The sulfide solid electrolyte containing halogen (hereinafter, also referred to as “solid electrolyte produced in the present invention”) produced by the production method of the present invention is halogen (F, Cl, Br, and I). 1 or more selected from the group consisting of) and sulfur (S), and any solid electrolyte having ionic conductivity may be used. However, from the viewpoint of enabling production of a solid electrolyte that exhibits excellent lithium ion conductivity, the solid electrolyte produced in the present invention is Li, A (A is at least one of P, Si, Ge, Al, and B). A solid electrolyte having S as a main component. Here, “main component” means that the total content of Li, A, and S contained in the solid electrolyte is 50 mol% or more. From the viewpoint of easily improving the lithium ion conducting performance, the total content of Li, A, and S contained in the solid electrolyte is preferably 60 mol% or more, and more preferably 70 mol% or more. . In addition, from the viewpoint of enabling the production of a solid electrolyte that exhibits excellent lithium ion conductivity, the solid electrolyte produced in the present invention is composed of 10 mol% or more and 35 mol% or less of halogen (F, Cl, Br, and I). 1 or more selected from the group consisting of:

Moreover, it is preferable that the solid electrolyte manufactured by this invention is equipped with the ion conductor which has Li, A, and S at least. Further, this ionic conductor has an ortho-composition anion structure (PS ₄ ³ -structure, SiS ₄ ⁴ -structure, GeS ₄ ⁴ -structure, AlS ₃ ³ described later) from the viewpoint of easily increasing the chemical stability. ^- structure, it is preferable that mainly the _BS ^{3 3-} structure). The ratio of the anion structure of the ortho composition is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more, based on the total anion structure in the ion conductor, 90 mol % Or more is particularly preferable. The ratio of the anion structure of the ortho composition can be determined by Raman spectroscopy, NMR, XPS, or the like. The solid electrolyte produced in the present invention preferably has the above ionic conductor and a LiX (X is a halogen element) component.

The solid electrolyte produced in the present invention is selected from the group consisting of Li ₂ S, sulfides of A, halogen-containing compounds (F-containing compounds, Cl-containing compounds, Br-containing compounds, and I-containing compounds). A solid electrolyte produced using a raw material composition containing at least one kind.). The raw material composition may further contain an O-containing compound.

Li ₂ S contained in the raw material composition preferably has few impurities. This is because side reactions can be suppressed. Examples of the method for synthesizing Li ₂ S include the method described in JP-A-7-330312. Furthermore, Li ₂ S is preferably purified using the method described in WO2005 / 040039. On the other hand, examples of the sulfide of A contained in the raw material composition include P ₂ S ₃ , P ₂ S ₅ , SiS ₂ , GeS ₂ , Al ₂ S ₃ , B ₂ S _{3 and the} like.

The F-containing compound that can be contained in the raw material composition is not particularly limited as long as it is a fluorine-containing compound, and examples thereof include LiF and LiPF ₆ . The Cl-containing compound that can be contained in the raw material composition is not particularly limited as long as it is a compound containing chlorine, and examples thereof include LiCl. Further, the Br-containing compound that can be contained in the raw material composition is not particularly limited as long as it is a compound containing bromine, and examples thereof include LiBr. The I-containing compound that can be contained in the raw material composition is not particularly limited as long as it is a compound containing iodine, and examples thereof include LiI. In addition, the O-containing compound that can be included in the raw material composition is not particularly limited as long as it is a compound that can break the bond of the bridging sulfur included in the coarse-grained raw material. For example, Li ₂ O, Li ₂ O ₂ , Na ₂ O, K ₂ O, MgO, CaO and the like can be mentioned, among which Li ₂ O is preferable. This is because O in Li ₂ O can efficiently cut bridging sulfur contained in the solid electrolyte. Further, for example, Li ₂ O added excessively has an advantage that hydrogen sulfide is not generated even if it is present in an unreacted state. Furthermore, since Li ₂ O has Li, it is possible to improve the Li ion conductivity of the solid electrolyte obtained by cutting the crosslinked sulfur.

Further, the solid electrolyte produced in the present invention, from the viewpoint of the small solid electrolyte of hydrogen sulfide generation amount, it is preferred not to substantially contain Li 2 _S. Li ₂ S reacts with water to generate hydrogen sulfide. For example, when the proportion of Li ₂ S contained in the raw material composition is large, Li ₂ S tends to remain. “Substantially free of Li ₂ S” can be confirmed by X-ray diffraction. Specifically, when it does not have a Li ₂ S peak (2θ = 27.0 °, 31.2 °, 44.8 °, 53.1 °), it is determined that it does not substantially contain Li ₂ S. can do.

Moreover, it is preferable that the solid electrolyte manufactured by this invention does not contain bridge | crosslinking sulfur substantially from a viewpoint made into a solid electrolyte with little hydrogen sulfide generation amount. Here, “crosslinked sulfur” refers to crosslinked sulfur in a compound obtained by reaction of Li ₂ S and sulfide of A. For example, Li ₂ S and _P 2 _{S 5} corresponds crosslinking sulfur reaction was _{S 3} PS-PS 3 comprising structure. Such bridging sulfur easily reacts with water and easily generates hydrogen sulfide. Furthermore, “substantially free of bridging sulfur” can be confirmed by measurement of a Raman spectrum. For example, in the case of a Li ₂ S—P ₂ S ₅ based solid electrolyte, the peak of the S ₃ P—S—PS ₃ structure usually appears at 402 cm ⁻¹ . Therefore, it is preferable that this peak is not detected. Moreover, the peak of PS ₄ ³⁻ structure usually appears at 417 cm ⁻¹ . In the present invention, the intensity I402 at 402 cm ^-1 is preferably smaller than the intensity I417 at 417 cm ^-1. More specifically, the strength I402 is preferably 70% or less, more preferably 50% or less, and even more preferably 35% or less with respect to the strength I417. As for the Li 2 _{S-P 2} S ₅ based non-solid electrolyte, to identify the unit containing the crosslinking sulfur, by measuring the peak of the unit, that is substantially free of bridging sulfur Judgment can be made.

Further, the solid electrolyte produced in the present invention, if substantially free of Li 2 _S and bridging sulfur, usually, the solid electrolyte has a composition of ortho-composition or the vicinity thereof. Here, ortho generally refers to one having the highest degree of hydration among oxo acids obtained by hydrating the same oxide. In the present invention, the crystal composition in which Li ₂ S is added most in the sulfide is called the ortho composition. For example, Li ₃ PS ₄ corresponds to the ortho composition in the Li ₂ S—P ₂ S ₅ system, Li ₃ AlS ₃ corresponds to the ortho composition in the Li ₂ S—Al ₂ S ₃ system, and Li ₂ S—B _2. In the S ₃ system, Li ₃ BS ₃ corresponds to the ortho composition, in the Li ₂ S—SiS ₂ system, Li ₄ SiS ₄ corresponds to the ortho composition, and in the Li ₂ S—GeS ₂ system, Li ₄ GeS _{4 corresponds} to the ortho composition. Applicable. In addition, when the solid electrolyte manufactured by this invention contains O, a part of S in the said ortho composition is substituted by O.

For example, in the case of a Li ₂ S—P ₂ S ₅ based solid electrolyte, the ratio of Li ₂ S and P ₂ S ₅ to obtain the ortho composition is Li ₂ S: P ₂ S ₅ = 75: 25 on a molar basis. is there. The same applies to the case of a Li ₂ S—Al ₂ S ₃ solid electrolyte and the case of a Li ₂ S—B ₂ S ₃ solid electrolyte. On the other hand, in the case of a Li ₂ S—SiS ₂ -based solid electrolyte, the ratio of Li ₂ S and SiS ₂ to obtain the ortho composition is Li ₂ S: SiS ₂ = 66.7: 33.3 on a molar basis. The same applies to a Li ₂ S—GeS ₂ solid electrolyte.

The raw material composition is, when containing Li ₂ S and _P 2 _{S 5,} the proportion of Li ₂ S to the total of Li ₂ S and _P 2 _{S 5} is preferably from 70 mol% or more 80 mol%, 72 mol % To 78 mol% or less, more preferably 74 mol% to 76 mol%. Incidentally, the raw material composition is, when containing Li ₂ S and _Al 2 _{S 3,} which is the same when containing Li ₂ S and _B 2 _{S 3.} On the other hand, the raw material composition is, when containing Li ₂ S and SiS _2, Li ₂ ratio of S to the total of Li ₂ S and SiS ₂ is preferably less than 62.5mol% 70.9mol% 63 mol% or more and 70 mol% or less is more preferable, and 64 mol% or more and 68 mol% or less is more preferable. The same applies to the case where the raw material composition contains Li ₂ S and GeS ₂ .

  Moreover, when the solid electrolyte manufactured by this invention is a solid electrolyte manufactured using the raw material composition containing LiX (X = F, Cl, Br, I), the ratio of LiX is 1 mol, for example % To 60 mol%, more preferably 5 mol% to 50 mol%, and still more preferably 10 mol% to 40 mol%. In the present invention, from the viewpoint of easily improving lithium ion conductivity, X is preferably at least one selected from the group consisting of Cl, Br, and I.

Examples of the shape of the solid electrolyte produced in the present invention include particles. The average particle diameter (D ₅₀ ) of the solid electrolyte produced in the present invention is preferably, for example, from 5 μm to 200 μm, and more preferably from 10 μm to 100 μm. In addition, the said average particle diameter can be determined with a particle size distribution meter, for example. Moreover, it is preferable that the solid electrolyte manufactured by this invention has high ionic conductivity, and it is preferable that the ionic conductivity in normal temperature is 1 * 10 < ^-4 > S / cm or more, for example, 1 * 10 < ^-3 >. More preferably, it is S / cm or more.

The average particle diameter (D ₅₀ ) of the sulfide solid electrolyte produced in the present invention is not particularly limited, but is preferably, for example, from 0.1 μm to 5 μm, and more preferably from 0.5 μm to 4 μm. preferable. In addition, an average particle diameter can be determined with a particle size distribution meter, for example.

  Moreover, it is preferable that the ionic conductivity of the coarse raw material is maintained in the sulfide solid electrolyte produced in the present invention. Specifically, for example, it is preferably 50% or more, more preferably 70% or more, still more preferably 80% or more, and 90% or more with respect to the ionic conductivity of the coarse raw material. It is particularly preferred. In addition, the ionic conductivity of the sulfide solid electrolyte can be determined by, for example, an AC impedance method.

  Moreover, the sulfide solid electrolyte manufactured by this invention can be used for the arbitrary uses which require ion conductivity. Especially, it is preferable that the said sulfide solid electrolyte is used for an all-solid-state battery (especially all-solid-state secondary battery). Furthermore, when the sulfide solid electrolyte is used for an all-solid battery, it may be used for a positive electrode active material layer, a negative electrode active material layer, or a solid electrolyte layer.

ADVANTAGE OF THE INVENTION According to this invention, the sulfide solid electrolyte manufactured with the manufacturing method mentioned above can be provided. In addition, it is possible to provide an all solid state battery in which the sulfide solid electrolyte is used in one or more layers selected from the group consisting of a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer. A partial cross section of such an all solid state battery is shown in FIG. For convenience, some of the reference numerals are omitted in FIG.
An all solid state battery 10 shown in FIG. 2 includes a positive electrode active material layer 1 and a negative electrode active material layer 2, a solid electrolyte layer 3 disposed therebetween, and a positive electrode current collector connected to the positive electrode active material layer 1. 4 and a negative electrode current collector 5 connected to the negative electrode active material layer 2. The positive electrode active material layer 1 has a positive electrode active material 1a, a sulfide solid electrolyte 6 containing halogen produced by the production method of the present invention, a binder 1b, and a conductive additive 1c. The negative electrode active material layer 2 includes a negative electrode active material 2a, a sulfide solid electrolyte 6, and a binder 2b. The solid electrolyte layer 3 includes a sulfide solid electrolyte 6 and a binder 3a. ing. When the sulfide solid electrolyte produced by the production method of the present invention is used in an all-solid battery, the composition other than the sulfide solid electrolyte (positive electrode active material, negative electrode active material, binder, conductive auxiliary agent, positive electrode current collector, and negative electrode The current collector and the like can be in a known form.

1. 1. Production of sulfide solid electrolyte containing halogen 1.1. Synthesis process (implemented in Examples, Reference Examples, and Comparative Examples)
As starting materials, lithium sulfide (Li ₂ S, manufactured by Nippon Kagaku Kogyo, purity 99.9%), diphosphorus pentasulfide (P ₂ S ₅ , manufactured by Aldrich, purity 99%) and lithium iodide (LiI, high purity chemical) Manufactured, purity 99%). Next, in a glove box under an Ar atmosphere (dew point −70 ° C.), Li ₂ S and P ₂ S ₅ have a molar ratio of 75Li ₂ S · 25P ₂ S ₅ (Li ₃ PS ₄ , ortho composition). Weighed as follows. Next, LiI was weighed so that the LiI ratio was 20 mol%. 2 g of these mixtures are put into a planetary ball mill container (45 cc, made of ZrO ₂ ), dehydrated heptane (moisture content of 30 ppm or less, 4 g) is added, and further ZrO ₂ balls (φ = 5 mm, 53 g) are added, The container was completely sealed (Ar atmosphere). This container was attached to a planetary ball mill (P7 made by Fritsch), and mechanical milling for 1 hour and 15 minutes of rest was repeated 40 times at a base plate rotation speed of 500 revolutions per minute. Thereafter, the obtained sample was dried at 120 ° C. for 2 hours so as to remove heptane on a hot plate to obtain a sulfide solid electrolyte (coarse raw material). The composition of the obtained sulfide solid electrolyte was x = 20 and y = 0.75 in the general formula xLiI · (100−x) (yLi ₂ S · (1-y) P ₂ S ₅ ).

1.2. Crystallization process (implemented in comparative example)
1 g of the coarse particle material obtained in the synthesis step was placed on an aluminum petri dish, and the coarse particle material was crystallized by holding it on a hot plate heated to 180 ° C. for 2 hours.

1.3. Micronization process (implemented in Examples, Reference Examples, and Comparative Examples)
The total weight of the coarse raw material obtained in the synthesis step or the coarse raw material crystallized in the crystallization step before the micronization step, dehydrated heptane (manufactured by Kanto Chemical) and dibutyl ether is 10 g, and the total Coarse grain raw material adjusted so that the ratio of the mass of the coarse grain raw material to the weight is a predetermined ratio (10%, 20%, 25%, 30%, 35%, 37.5%, or 40%), Dehydrated heptane and dibutyl ether and 40 g of ZrO ₂ balls (φ0.3 mm, φ0.6 mm, or φ1 mm) were put into a 45 ml ZrO ₂ pot, and the pot was completely sealed (Ar atmosphere). This pot is attached to a planetary ball mill (P7 made by Fritsch), and at a predetermined rotation speed (90 revolutions per minute, 150 revolutions per minute, 200 revolutions per minute, or 300 revolutions per minute) for a predetermined time ( By performing wet mechanical milling for 10 hours, 15 hours, 20 hours, or 100 hours), the coarse raw material was pulverized to obtain a sulfide solid electrolyte material.

1.4. Crystallization process (implemented in Examples and Reference Examples)
By placing 1 g of a sulfide solid electrolyte finely divided in a fine particle formation step on an aluminum petri dish and holding it on a hot plate heated to 180 ° C. for 2 hours, the fine particle sulfide The solid electrolyte was crystallized.
The manufacturing conditions of Examples 1 to 4 and Comparative Examples 1 to 3 are shown in Table 1, and the manufacturing conditions of Examples 5 to 10 and Reference Examples 1 to 3 are shown in Table 2, respectively. Tables 1 and 2 also show the total grinding energy in the micronization step.

2. Particle size distribution measurement A small amount of the crystallized particulate sulfide solid electrolyte is sampled, and particle size distribution measurement is performed with a laser scattering / diffraction particle size distribution analyzer (Nikkiso Microtrac MT 3300EXII), and the average particle diameter (D ₅₀ ). It was determined. The results are shown in Tables 3 and 4.

3. X-ray diffraction measurement A small amount of crystallized fine particulate sulfide solid electrolyte (Examples 1 to 12, Comparative Examples 1 to 3, and Reference Examples 1 to 3) was placed in an unexposed jig. The powder XRD measurement was performed in the range of 2θ = 10 ° to 60 ° in an inert atmosphere of Ar gas. For powder XRD measurement, an X-ray diffractometer (smart-lab manufactured by Rigaku) was used to investigate the presence or absence of crystals formed by separating halogen. The results are shown in Tables 3 and 4. Moreover, the result of the powder XRD measurement with respect to the crystallized particulate sulfide solid electrolyte (Examples 7 to 11 and Reference Examples 1 to 3) is shown in FIG.

4). Lithium ion conductivity measurement The lithium ion conductivity of the sulfide solid electrolytes obtained in Examples 1 to 12, Comparative Examples 1 to 3 and Reference Examples 1 to 3 was measured. Specifically, a 1 cm ² , 0.5 mm thick pellet was prepared using the sulfide solid electrolyte recovered after the crystallization step, molded at 4.3 ton, and then AC impedance was applied to the molded pellet. The lithium ion conductivity (at room temperature) was measured by the method. In addition, the solartron 1260 was used for the measurement, the measurement conditions were an applied voltage of 5 mV, a measurement frequency range of 0.01 MHz to 1 MHz, a resistance value of 100 kHz was read, corrected by thickness, and converted into lithium ion conductivity. The results are shown in Tables 3 and 4 and FIGS.

5. Results As shown in Table 3 and FIG. 4, the sulfide solid electrolyte containing halogen (Examples 1 to 4) manufactured by the manufacturing method of the present invention in which the crystallization process is performed after the micronization process is performed in the crystallization process. The lithium ion conductivity was higher than that of the halogen-containing sulfide solid electrolyte (Comparative Examples 1 to 3) produced by performing the micronization step after the step, and had excellent lithium ion conductivity. From this result, it was confirmed that according to the production method of the present invention, a fine particle sulfide solid electrolyte containing halogen having improved ion conduction performance can be produced. As shown in Table 3, the average particle diameters of Examples 1 to 4 and Comparative Examples 1 to 3 were all fine particles.

  In addition, as shown in Table 4, FIG. 3 and FIG. 4, the coarse raw material in the fine particle process in which the total pulverization energy per unit weight of the coarse raw material is 400 kJ · sec / g or more and 2000 kJ · sec / g or less. In Examples 5 to 10 in which the mass ratio X of 0.1 ≦ X ≦ 0.35 was higher than that of Reference Examples 1 to 3 in which X> 0.35, the lithium ion conductivity was higher. In Examples 5 to 10, crystals formed by separating halogen were not confirmed, but in Reference Examples 1 to 3, this crystal was confirmed. From this result, in the microparticulation process performed before the crystallization process, the mass ratio X of the coarse raw material is set to 0.1 ≦ X ≦ 0.35, and is performed before the crystallization process. The micronization step is a wet media type pulverization treatment in which the total pulverization energy per unit weight of the coarse raw material is 400 kJ · sec / g or more and 2000 kJ · sec / g or less, thereby improving lithium ion conductivity. It was confirmed that it was easy to produce a sulfide solid electrolyte containing halogen.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode active material layer 1a ... Positive electrode active material 1b, 2b, 3a ... Binder 1c ... Conductive support agent 2 ... Negative electrode active material layer 2a ... Negative electrode active material 3 ... Solid electrolyte layer 4 ... Positive electrode collector 5 ... Negative electrode current collector Body 6 ... sulfide solid electrolyte 10 ... all solid state battery

Claims (3)

A synthesis step of synthesizing a coarse raw material of a sulfide solid electrolyte containing halogen;
In the volume-based particle size distribution of the synthesized coarse raw material measured by a particle size distribution measuring apparatus based on the laser diffraction / scattering method, the median diameter D ₅₀ corresponding to 50% by volume cumulative from the fine particle side is 5 μm or less. A micronization process to micronize until
And a crystallization step of crystallizing the finely divided sulfide solid electrolyte. A method for producing a sulfide solid electrolyte.
The micronization step is a step of micronizing by a wet media type pulverization process,
The ratio X of the mass of the coarse raw material in the total mass of the solvent, the additive, and the coarse raw material used in the wet media-type grinding treatment is 0.1 ≦ X ≦ 0.35. 2. A method for producing a sulfide solid electrolyte according to 1. The micronization step is a step in which a planetary ball mill is used, and
The total pulverization energy E per unit weight of the coarse-grained raw material defined by the following formula (1) is a step of forming fine particles within a range of 400 kJ · sec / g to 2000 kJ · sec / g. Item 3. A method for producing a sulfide solid electrolyte according to Item 2.
E = 1/2 nmv ² / s · t Formula (1)
(N is the number of media (pieces), m is the weight (kg) per media, v is the speed of the media (m / s), s is the amount of coarse raw material (g), and t is the processing time (seconds) )