JP2016134316A - Solid electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolyte of high ionic conductivity.SOLUTION: The solid electrolyte includes a sulfide solid electrolyte and LiBHin which solid solution of LiX is formed. In the formula, X represents a halogen atom, -NR, or -NR. Rs respectively represent a hydrogen atom and an alkyl group.SELECTED DRAWING: None

Description

  The present invention relates to a solid electrolyte, a solid electrolyte molded body, an all-solid battery using the same, and a method for producing the solid electrolyte molded body.

  Known sulfide solid electrolytes are those synthesized from lithium sulfide and phosphorus sulfide, and those added with halides (Patent Documents 1 to 3).

Complex hydrides such as LiBH ₄ composed of light elements have been widely studied as high-density hydrogen storage materials, but in recent years their use as solid electrolytes has been studied (Patent Document 4, Non-Patent Document 1). . The complex hydride is advantageous in that it is lightweight and has a high potential, is stable and hardly decomposes thermally, and is easily deformed. However, there is a drawback that the ionic conductivity is lower than that of the sulfide solid electrolyte.

JP 2005-228570 A JP 2010-199033 A JP 2013-016423 A International Publication No. 2009/139382 Pamphlet

Applied Physics Vol.83 No.2 2014

In order to improve the performance of all-solid-state batteries, further improvements in ionic conductivity are desired for solid electrolytes used in solid electrolyte layers and electrode mixture layers.
An object of the present invention is to provide a solid electrolyte having high ion conductivity.

As a result of intensive studies, the present inventors have found that ionic conductivity is improved by combining a specific complex hydride and a sulfide solid electrolyte.
According to the present invention, the following solid electrolyte and the like are provided.
1. A sulfide solid electrolyte,
LiBH ₄ in which LiX is dissolved,
Containing solid electrolyte.
(In the formula, X represents a halogen atom, —NR ₂ or —N ₂ R. R represents a hydrogen atom or an alkyl group, respectively.)
2. 2. The solid electrolyte according to 1, wherein the sulfide solid electrolyte and LiBH ₄ in which LiX is dissolved are powders.
3. The sulfide solid electrolyte is
A solid electrolyte obtained from Li ₂ S and P ₂ S ₅ ;
A solid electrolyte obtained from Li ₂ S, GeS ₂ and P ₂ S ₅ ;
The solid electrolyte according to 1 or 2, which is one or more solid electrolytes selected from a solid electrolyte obtained from Li ₂ S, P ₂ S ₅ and LiX ′, and an aldilodite-type Li ₆ PS ₅ X ′ solid electrolyte. (In the formula, X ′ represents a halogen atom.)
A solid electrolyte molded body obtained by pressure-molding the solid electrolyte according to any one of 4.1 to 3.
An all solid state battery including the solid electrolyte formed body according to 5.4.
6). Manufacture of a solid electrolyte molded body including a step of pressure-molding a composition comprising a sulfide solid electrolyte powder and a LiBH ₄ powder in which LiX is dissolved, and a step of heat-treating the obtained molded body Method.

  According to the present invention, a solid electrolyte having high ionic conductivity can be provided.

It is a schematic sectional drawing which shows one Embodiment of an all-solid-state battery.

1. Solid Electrolyte The solid electrolyte of the present invention includes a sulfide solid electrolyte and LiBH _{4 in} which LiX is dissolved. X represents a halogen atom, —NR ₂ or —N ₂ R. R represents a hydrogen atom or an alkyl group.
The solid electrolyte of the present invention has high ionic conductivity. Therefore, the all-solid battery using the solid electrolyte of the present invention can achieve high output.

Hereinafter, each component etc. are demonstrated.
[Sulfide solid electrolyte]
The sulfide solid electrolyte includes those containing an alkali metal element, phosphorus and sulfur as constituent components, and may further contain a halogen.
The shape of the sulfide solid electrolyte is not particularly limited, but is preferably a powder.

The sulfide solid electrolyte preferably has a composition represented by the following formula (1).
_{L a M b P c S d} X e O f ··· (1)
(In the formula, L represents an alkali metal.
M represents B, Al, Si, Ge, As, Se, Sn, Sb, Te, Pb, Bi, or a combination thereof.
X represents I, Cl, Br, F, or a combination thereof.
a to f satisfy 0 <a ≦ 12, 0 ≦ b ≦ 0.2, c = 1, 0 <d ≦ 9, 0 <e ≦ 9, and 0 ≦ f ≦ 9, respectively. )

In the formula (1), a to f indicate the composition ratio of each element, and 0 <a ≦ 12, 0 ≦ b ≦ 0.2, c = 1, 0 <d ≦ 9, 0 <e ≦ 9, 0 ≦ f ≦ 9 is satisfied.
In the formula (1), preferably, b is 0, and more preferably, the ratio of a, c, d, e and f (a: c: d: e: f) is a: c: d: e: f = 1 to 9: 1: 3 to 7: 0.05 to 3: 0 to 2, more preferably, a: c: d: e: f = 2 to 6.5: 1: 3.5 5: 0.1-1.5: 0-1. Most preferably, a: c: d: e: f = 2 to 6.5: 1: 3.5 to 4.95: 0.1 to 1.5: 0 to 0.5. d is preferably 4.
When f is not 0, it is desirable to add so that d + f = 4.
The composition ratio of each element can be controlled by adjusting the compounding amount of the raw material compound when producing the solid electrolyte or the solid electrolyte precursor (solid electrolyte glass).

The solid electrolyte having the composition represented by the formula (1) is preferably a solid electrolyte having a composition represented by the following formula (1 ′).
_{L a M b P c S d} X e ··· (1 ')
(In the formula, L represents an alkali metal.
M represents B, Al, Si, Ge, As, Se, Sn, Sb, Te, Pb, Bi, or a combination thereof.
X represents I, Cl, Br, F, or a combination thereof.
a to e satisfy 0 <a ≦ 12, 0 ≦ b ≦ 0.2, c = 1, 0 <d ≦ 9, and 0 <e ≦ 9, respectively. )

In the formula (1 ′), a to e each indicate a composition ratio of each element, and 0 <a ≦ 12, 0 ≦ b ≦ 0.2, c = 1, 0 <d ≦ 9, and 0 <e ≦ 9. Fulfill.
Preferably, b is 0, and more preferably, the ratio of a, c, d, e (a: c: d: e) is a: c: d: e = 1-9: 1: 3-7: It is 0.05-3, More preferably, it is a: c: d: e = 2-6.5: 1: 3.5-5: 0.1-1.5. Most preferably, a: c: d: e = 2 to 6.5: 1: 3.5 to 4.95: 0.1 to 1.5.
d is preferably 4.
A solid electrolyte having an argilodite-type Li ₆ PS ₅ X composition is also preferable.

_{L a M b P c S d} X e O f and _L a _M b _P c _S each element constituting the solid electrolyte represented by d _{X e} are preferably as follows.
The alkali metal of L includes one or more selected from Li, Na, K, Rb, Ce and Fr, preferably one or more selected from Li and Na, and more preferably Li.
M is preferably B, Al, Si, Ge or a combination thereof.
X is preferably I, Br or Cl, more preferably Br.

[Production Method of Sulfide Solid Electrolyte]
(1) Raw material A sulfide solid electrolyte can be prepared by using, for example, the following components (A) and (B), or (A), (B) and (C).
(A) an alkali metal sulfide (B) M _'m S _n compound represented by _{(C) M''w X} x compound represented by (wherein, M' is, Li, Na, B, Al , Si , P, Ge, or a combination thereof.
M ″ represents Li, Na, B, Al, Si, P, S, Ge, As, Se, Sn, Sb, Te, Pb, Bi, or a combination thereof.
X represents F, Cl, Br, I, or a combination thereof.
w represents an integer of 1 or 2.
m, n and x each represent an integer of 1 to 10. )

  Each of the components (A), (B) and (C) may be used alone or in combination of two or more.

The (A) alkali metal sulfide, _Li 2 S (lithium sulfide), _Na 2 S (sodium sulfide) and the like, preferably lithium sulfide.
Lithium sulfide can be used without particular limitation, but high purity is preferred. For example, it can be produced by the methods described in JP-A-7-330312, JP-A-9-283156, JP-A 2010-163356, JP-A 2011-84438, and JP-A 2011-136899. it can.

Specifically, lithium hydroxide and hydrogen sulfide are reacted at 70 ° C. to 300 ° C. in a hydrocarbon-based organic solvent to produce lithium hydrosulfide, and then the reaction solution is dehydrosulfurized to form lithium sulfide. Can be synthesized (Japanese Patent Laid-Open No. 2010-163356).
In addition, lithium hydroxide and hydrogen sulfide are reacted at 10 ° C. to 100 ° C. in an aqueous solvent to produce lithium hydrosulfide, and then the reaction liquid is dehydrosulfurized to synthesize lithium sulfide (special feature). No. 2011-84438).

The lithium sulfide preferably has a total lithium oxide lithium salt content of 0.15% by mass or less, more preferably 0.1% by mass or less, and a lithium N-methylaminobutyrate content. The content is preferably 0.15% by mass or less, more preferably 0.1% by mass or less. When the total content of the lithium salt of sulfur oxide is 0.15% by mass or less, the solid electrolyte obtained by the melt quenching method or the mechanical milling method becomes a glassy electrolyte (fully amorphous). On the other hand, when the total content of the lithium salt of sulfur oxide exceeds 0.15% by mass, the obtained electrolyte may become a crystallized product from the beginning.
Further, when the content of lithium N-methylaminobutyrate is 0.15% by mass or less, lithium N-methylaminobutyrate does not deteriorate the cycle performance of the lithium ion battery. When lithium sulfide with reduced impurities is used, a high ion conductive electrolyte can be obtained.

When lithium sulfide is produced based on the above-mentioned JP-A-7-330312 and JP-A-9-283156, it is preferable to purify lithium sulfide because it contains a lithium salt of sulfur oxide.
On the other hand, lithium sulfide produced by the method for producing lithium sulfide described in Japanese Patent Application Laid-Open No. 2010-163356 may be used without purification because it contains a very small amount of lithium oxide lithium salt.
As a preferable purification method, for example, the purification method described in International Publication No. 2005/40039 and the like can be mentioned. Specifically, the lithium sulfide obtained as described above is washed at a temperature of 100 ° C. or higher using an organic solvent.

(B) Examples of the compound represented by _{M 'm S n, P 2} S 3 ( trisulfide _{diphosphorus),} P 2 _{S 5} (phosphorus pentasulfide), SiS ₂ (sulfide _silicon), Al _{2 S} 3 ( Aluminum sulfide), GeS ₂ (germanium sulfide), B ₂ S ₃ (diarsenic trisulfide), Na ₂ S (sodium sulfide) and the like can be mentioned, and P ₂ S ₅ is preferable.
As long as diphosphorus pentasulfide (P ₂ S ₅ ) is industrially manufactured and sold, it can be used without particular limitation.

(C) The compound represented by M ″ _w X _x is preferably a compound in which M ″ is lithium or phosphorus.
Specifically, the compound represented by (C) M ″ _w X _x which is a compound containing a halogen element includes LiF, LiCl, LiBr, LiI, BCl ₃ , BBr ₃ , BI ₃ , AlF ₃ , AlBr ₃ , _{AlI 3, AlCl 3, SiF 4} , SiCl 4, SiCl 3, Si 2 Cl 6, SiBr 4, SiBrCl 3, SiBr 2 Cl 2, SiI 4, PF 3, PF 5, PCl 3, PCl 5, PBr 3, PI ₃ , P ₂ Cl ₄ , P ₂ I ₄ , SF ₂ , SF ₄ , SF ₆ , S ₂ F ₁₀ , SCl ₂ , S ₂ Cl ₂ , S ₂ Br ₂ , GeF ₄ , GeCl ₄ , GeBr ₄ , GeI _{4 , GeF 2, GeCl 2, GeBr} 2, GeI 2, AsF 3, AsCl 3, AsBr 3, AsI 3, AsF 5, SeF 4, SeF _{, SeCl 2, SeCl 4, Se} 2 Br 2, SeBr 4, SnF 4, SnCl 4, SnBr 4, SnI 4, SnF 2, SnCl 2, SnBr 2, SnI 2, SbF 3, SbCl 3, SbBr 3, SbI 3 _{, SbF 5, SbCl 5, PbF} 4, PbCl 4, PbF 2, PbCl 2, PbBr 2, PbI 2, BiF 3, BiCl 3, BiBr 3, BiI 3, TeF 4, Te 2 F 10, TeF 6, TeCl 2 , TeCl ₄ , TeBr ₂ , TeBr ₄ , TeI ₄ , NaI, NaF, NaCl, NaBr and the like, preferably LiCl, LiBr, LiI, PCl ₅ , PCl ₃ , PBr ₅ and PBr ₃ , more preferably LiCl. , LiBr, is LiI and PBr _3.
In place of the component (C), an oxide of a compound represented by the formula (C) such as POCl ₃ or POBr ₃ can also be used.

Of the above components, preferably, a solid electrolyte obtained from Li ₂ S and P ₂ S ₅ , a solid electrolyte obtained from Li ₂ S, GeS ₂ and P ₂ S ₅ , Li ₂ S, P ₂ S ₅ and LiX ′. A solid electrolyte obtained from is preferred.

  The solid electrolyte having the composition represented by the formula (1) is a compound of the formula (1) containing an oxygen element by using a vitrification accelerator described later, even if the component (C) is a compound not containing an oxygen element. Can be produced.

The molar ratio of components (A) :( B) is, for example, 65:35 to 85:15, preferably (A) :( B) = 67: 33 to 83:17 (molar ratio), Preferably (A) :( B) = 67: 33 to 80:20 (molar ratio), most preferably (A) :( B) = 72: 28 to 78:22 (molar ratio).
At this time, the ratio of the molar amount of (C) to the total molar amount of components (A) and (B) is preferably 50:50 to 99: 1, more preferably [(A) + ( B)] :( C) = 55: 45 to 97: 3 (molar ratio), more preferably [(A) + (B)] :( C) = 60: 40 to 96: 4 (molar ratio). Especially preferably, [(A) + (B)] :( C) = 70: 30 to 96: 4 (molar ratio).
The above molar ratio is particularly preferred when M ″ of component (C) is other than phosphorus.

The molar ratio of components (A) :( B) is, for example, 60:40 to 90:10, preferably (A) :( B) = 70: 30 to 90:10 (molar ratio). More preferably, (A) :( B) = 72: 28 to 88:12 (molar ratio), and still more preferably (A) :( B) = 74: 26 to 86:14 (molar ratio). Particularly preferably, (A) :( B) = 75: 25 to 85:15 (molar ratio), most preferably component (A) is lithium sulfide and component (B) is diphosphorus pentasulfide. (A) :( B) = 77: 23 to 83:17 (molar ratio).
At this time, the ratio of the molar amount of (C) to the total molar amount of components (A) and (B) is preferably 50:50 to 99: 1, more preferably [(A) + ( B)] :( C) = 80: 20 to 98: 2 (molar ratio), more preferably [(A) + (B)] :( C) = 85: 15 to 98: 2 (molar ratio). Particularly preferably, [(A) + (B)] :( C) = 90: 10 to 98: 2.
The above molar ratio is particularly preferred when M ″ of component (C) is phosphorus.

In addition to the component (A), the component (B) and the component (C) which is a compound containing a halogen element, a compound (vitrification accelerator) for reducing the glass transition temperature may be added. Examples of vitrification promoters include Li ₃ PO ₄ , Li ₄ SiO ₄ , Li ₄ GeO ₄ , Li ₃ BO ₃ , Li ₃ AlO ₃ , Li ₃ CaO ₃ , Li ₃ InO ₃ , Na ₃ PO ₄ , Na Examples include inorganic compounds such as ₄ SiO ₄ , Na ₄ GeO ₄ , Na ₃ BO ₃ , Na ₃ AlO ₃ , Na ₃ CaO ₃ , and Na ₃ InO ₃ .

(2) Manufacturing method of glassy solid electrolyte A glassy solid electrolyte can be manufactured with the following method using said component (A)-(C) and the vitrification promoter etc. arbitrarily.
A glassy solid electrolyte is produced by mixing raw materials (for example, lithium sulfide, diphosphorus pentasulfide, and halogen compound) at the above-mentioned blending ratio and treating them according to any of the following (i) to (vii). Can do.
Hereinafter, each manufacturing method will be described.

(I) Melting and quenching method The melting and quenching method is a method of obtaining a glassy solid electrolyte by mixing a predetermined amount of raw materials, reacting them at a predetermined temperature, and then rapidly cooling them.
For example, a mixture of pellets in a mortar is placed in a carbon-coated quartz tube and vacuum-sealed. After making it react at a predetermined reaction temperature, it is put into ice and rapidly cooled to obtain a glassy solid electrolyte.
The reaction temperature is preferably 400 ° C to 1000 ° C, more preferably 800 ° C to 900 ° C.
The reaction time is preferably 0.1 hour to 12 hours, more preferably 1 to 12 hours.
The quenching temperature of the reactant is usually 10 ° C. or less, preferably 0 ° C. or less, and the cooling rate is usually about 1 to 10,000 K / sec, preferably 10 to 10,000 K / sec.

(Ii) Mechanical milling method (MM method)
The MM method is a method of obtaining a glassy solid electrolyte by mixing a predetermined amount of raw materials and applying mechanical energy.
A method for applying mechanical energy is not particularly limited, and various ball mills can be exemplified.
For example, by mixing a predetermined amount of diphosphorus pentasulfide (P ₂ S ₅ ), lithium sulfide (Li ₂ S) and a halogen compound in a mortar and reacting them for a predetermined time using, for example, various ball mills, a glassy state is obtained. The solid electrolyte is obtained.
The MM method using the above raw materials can be reacted at room temperature. Therefore, there is an advantage that a glassy solid electrolyte having a charged composition can be obtained without thermal decomposition of the raw material.
Further, the MM method has an advantage that it can be finely powdered simultaneously with the production of the glassy solid electrolyte.

Various types such as a rotating ball mill, a rolling ball mill, a vibrating ball mill, and a planetary ball mill can be used for the MM method.
As conditions for the MM method, for example, when a planetary ball mill is used, the rotational speed may be set to several tens to several hundreds of revolutions / minute, and the treatment may be performed for 0.5 hours to 100 hours.
The balls of the ball mill may be used by mixing balls having different diameters.
Moreover, you may adjust the temperature in the mill in the case of MM processing.
The raw material temperature during MM treatment may be heated from room temperature to 200 ° C. as necessary.

(Iii) Solid phase method The solid phase method is a method of obtaining a glassy solid electrolyte by mixing raw materials and heating at a predetermined temperature. For example, by mixing a predetermined amount of diphosphorus pentasulfide (P ₂ S ₅ ), lithium sulfide (Li ₂ S), and a halogen compound in a mortar and heating at a temperature of 100 to 900 ° C., a glassy solid electrolyte is obtained. Is obtained

(Iv) Solution Method The solution method is a method for producing a glassy solid electrolyte by contacting a raw material in a solvent.
According to the solution method, a glassy solid electrolyte can be produced without using special equipment such as a mechanical milling device. Therefore, a conductive material can be manufactured at a low cost. Moreover, since mechanical milling is not performed, it is possible to prevent generation of impurities due to peeling of the wall surface of the mechanical milling device.
Further, since no mechanical milling device is used, there is no disadvantage that raw materials and solid electrolytes adhere to the balls and the mill vessel.

The solvent is preferably an organic solvent, more preferably an aprotic solvent, and still more preferably a hydrocarbon organic solvent.
Examples of the aprotic solvent include aprotic organic solvents (for example, hydrocarbon-based organic solvents), aprotic polar organic compounds (for example, amide compounds, lactam compounds, urea compounds, organic sulfur compounds, and cyclic organic phosphorus compounds). Etc.), and any one of them can be used as a single solvent or a mixed solvent composed of two or more of these.

As the hydrocarbon solvent, saturated hydrocarbon, unsaturated hydrocarbon, or aromatic hydrocarbon can be used.
Examples of the saturated hydrocarbon include hexane, pentane, 2-ethylhexane, heptane, decane, and cyclohexane.
Examples of the unsaturated hydrocarbon include hexene, heptene, cyclohexene and the like.
Aromatic hydrocarbons include toluene, xylene, decalin, 1, 2, 3, 4-tetrahydronaphthalene and the like.
As the hydrocarbon solvent, toluene and xylene are particularly preferable.

  The aprotic solvent and the hydrocarbon solvent are preferably dehydrated in advance. Specifically, the water content is preferably 100 ppm by weight or less, and particularly preferably 30 ppm by weight or less.

You may add another solvent to the solvent used as needed.
Specific examples of the other solvents include ketones such as acetone and methyl ethyl ketone; ethers such as tetrahydrofuran; alcohols such as ethanol and butanol; esters such as ethyl acetate; dichloromethane, chlorobenzene, heptane fluoride, fluoride Halogenated hydrocarbons such as fluorinated compounds such as benzene, 2,3-dihydroperfluoropentane, 1,1,2,2,3,3,4-heptafluorocyclopentane, and the like.

  The solvent used by the above-mentioned solution method can be used similarly for the solvent used by the manufacturing method mentioned later.

  The amount of the solvent is preferably such that the raw material becomes a solution or slurry by the addition of the solvent. Usually, the addition amount of the raw material (total amount) with respect to 1 liter of solvent is about 0.001 kg to 1 kg. Preferably they are 0.005 Kg or more and 0.5 Kg or less, Especially preferably, they are 0.01 Kg or more and 0.3 Kg or less.

The method for contacting the raw materials in a solvent is not particularly limited. For example, there is a method of stirring a mixture of a raw material and a solvent in a container having a stirring device, and stirring is preferably performed at the time of contact.
The temperature during the contact (reaction) step is usually 50 ° C. or higher and 300 ° C. or lower, preferably 60 ° C. or higher and 250 ° C. or lower, more preferably 70 ° C. or higher and 200 ° C. or lower.
Moreover, the time at the time of a contact process is 5 minutes or more and 200 hours or less normally, Preferably they are 10 minutes or more and 100 hours or less. If the time during the contacting step is less than 5 minutes, the reaction may be insufficient. If the contact time is too short, the raw material may remain.
Note that the temperature and time may be combined using several conditions as steps. For example, contact may be performed at 100 ° C. for 1 hour from the start of contact, and heated at 150 ° C. for 10 hours after 1 hour.

  The contacting step is preferably carried out in an inert gas atmosphere such as nitrogen or argon. The dew point of the inert gas is preferably −20 ° C. or less, particularly preferably −40 ° C. or less. The pressure is usually normal pressure to 100 MPa, preferably normal pressure to 20 MPa.

  After the contact treatment, the generated solid portion and the solvent are separated to recover the glassy solid electrolyte. Separation can be performed by a known method such as decantation, filtration, drying, or a combination thereof.

(V) Wet mechanical milling method (wet MM method)
The wet mechanical milling method is a method in which a raw material is manufactured by mechanical milling in a solvent.
In the wet mechanical milling method, the mechanical milling process is performed in a state where a solvent is added, thereby suppressing the effect of increasing the grain size during the process and efficiently promoting the synthesis reaction. Thereby, it is possible to obtain a glassy solid electrolyte having excellent uniformity and low content of unreacted raw materials. Further, it is possible to prevent the raw materials and reactants from sticking to the vessel wall and the like, and to improve the product yield.

  The amount of the solvent is preferably such that the raw material becomes a solution or slurry by the addition of the solvent. Usually, the amount of the raw material (total amount) added per liter of solvent is 0.01 kg or more and 1 kg or less. Preferably they are 0.1 kg or more and 1 kg or less, Most preferably, they are 0.2 kg or more and 0.8 kg or less.

Various types of grinding methods can be used for the wet mechanical milling treatment. In particular, it is preferable to use a planetary ball mill.
The planetary ball mill can efficiently generate very high impact energy by rotating the platform while the pot rotates. Also preferred is a bead mill.

The rotation speed and rotation time of the wet mechanical milling process are not particularly limited, but the higher the rotation speed, the faster the production rate of the glassy solid electrolyte, and the longer the rotation time, the conversion rate of the raw material to the glassy solid electrolyte Becomes higher. However, if the rotational speed of the mechanical milling process is increased, the burden on the pulverizer may be increased. If the rotation time is increased, it takes time to produce a glassy electrolyte.
The balls of the ball mill may be used by mixing balls having different diameters.
In addition to the above, the temperature in the mill during MM processing may be adjusted. As conditions for the MM method, for example, when a planetary ball mill is used, the rotational speed may be set to several tens to several hundreds of revolutions / minute, and the treatment may be performed for 0.5 hours to 100 hours.

Since mechanical milling is performed in the presence of a solvent, the processing time can be shortened. You may heat from room temperature to 200 degreeC as needed.
The resulting product after the mechanical milling treatment is dried and the solvent is removed to obtain a glassy solid electrolyte.

(Vi) Slurry synthesis method The slurry synthesis method comprises a mechanical energy supply means for imparting mechanical energy to a raw material in a solvent, a contact means for contacting the raw material in a solvent, a mechanical energy supply means and a contact means. A glassy solid electrolyte using a manufacturing apparatus comprising: a connecting means for connecting the two materials; and a circulating means for circulating the raw material and / or a reactant of the raw material between the mechanical energy supplying means and the contacting means through the connecting means It is a method of manufacturing. By drying the reaction product and removing the solvent, a glassy solid electrolyte is obtained.
The said raw material and solvent can use the same thing as the raw material and solvent of a wet mechanical milling method.

  In the slurry synthesis method, the reaction is performed with a solvent added to the raw material. By making it react in the state which added the solvent, the granulation effect at the time of a process can be suppressed and a synthesis reaction can be accelerated | stimulated efficiently. Thereby, it is possible to obtain a glassy solid electrolyte having excellent uniformity and low content of unreacted raw materials. Further, it is possible to prevent the raw materials and reactants from sticking to the vessel wall and the like, and to improve the product yield.

(Vii) Alternate implementation of mechanical milling method and solution method Alternate implementation of mechanical milling method and contact method includes a step of mechanically milling the raw material and a contact step of contacting the raw material in a solvent, and the mechanical milling treatment step And the contact step is repeated alternately.

In the mechanical milling process, various types of pulverization methods exemplified by the MM method can be used.
The rotation speed and rotation time of the mechanical milling process are not particularly limited, but the faster the rotation speed, the faster the glassy solid electrolyte production rate, and the longer the rotation time, the conversion rate of the raw material to the glassy solid electrolyte is Get higher. For example, when a planetary ball mill is used, the rotational speed may be 250 rpm / min to 300 rpm / min, and the treatment may be 5 minutes to 50 hours.
The treatment time indicates the time during which the raw material and the glassy solid electrolyte remain in the planetary ball mill. Accordingly, the raw material and the glassy solid electrolyte circulate through the planetary ball mill and the reaction vessel, but the total time that the raw material and the glassy solid electrolyte stay in the planetary ball mill from the start to the end of the reaction.
If the above time is short, unreacted raw materials may remain, and if the above time is long, the capacity of the pulverizer is increased, the amount of raw materials and glassy solid electrolyte that can be stored at one time is increased, or the following reaction is completed. There is a possibility that a problem that the time until the time becomes longer may occur.

The time for the contacting step is preferably from 5 minutes to 200 hours.
Here, the time of the said contact process shows the time when the raw material and the glassy solid electrolyte remain in the reaction tank. Accordingly, the raw material and the glassy solid electrolyte circulate in the planetary ball mill and the reaction tank, but the total time that the raw material and the glassy solid electrolyte remain in the reaction tank from the start to the end of the reaction.

  The mechanical milling process and the contact process described above are repeated alternately. The number of repetitions is preferably 2 or more and 100 or less. More preferably, the number of repetitions is 5 or more and 100 or less, and further preferably 10 or more and 100 or less.

  As mentioned above, although the manufacturing method of glassy solid electrolyte was demonstrated, even if it is a case of any of the above-mentioned manufacturing methods, the order (order to contact) which mixes a raw material is not specifically limited.

The obtained sulfide-based glass may be fired and crystallized to obtain a lithium ion conductive sulfide-based crystallized glass.
A calcination temperature is 150 to 360 degreeC, for example, and 180 to 350 degreeC is especially preferable. The firing time is not particularly limited as long as the crystal is generated, and may be instantaneous or long. Moreover, there is no limitation in particular also about the temperature rising pattern to baking temperature.

[LiBH ₄ in which LiX is dissolved]
In the present invention, a complex hydride LiBH _{4 in} which a lithium compound LiX is dissolved is used. Hereinafter, this component may be referred to as “LiBH ₄ —LiX solid solution”.
Solid solution and while maintaining the crystal structure illustrated is LiBH _4, lithium compound LiX is, say that it has replaced part of the crystal structure of LiBH _4.
The solid solution is confirmed by the fact that the peak position obtained by X-ray diffraction measurement (XRD) is shifted from the LiBH ₄ peak position.

X represents a halogen atom, —NR ₂ or —N ₂ R. R represents a hydrogen atom or an alkyl group. _Two Rs in —NR ₂ may be the same or different.

The shape of the solid solution of the complex hydride can be easily changed. The solid electrolyte of the present invention is obtained by adding such a complex hydride solid solution to a sulfide solid electrolyte, thereby converting the solid electrolyte into a sheet (for example, a solid electrolyte layer of an all-solid battery, a solid electrolyte of an electrode mixture layer, an ion In the case of a solid electrolyte or the like of a sheet sample for measuring conductivity), a gap between sulfide solid electrolyte powders can be filled with a complex hydride and consolidated, and heat fusion such as Li ₇ P ₃ S ₁₁ can be performed. Since the interface resistance is lowered, the ionic conductivity is improved.

LiBH not particularly limited as _4, it can be used conventionally known which are used as the reducing agent and the hydrogen storage medium. The purity of LiBH ₄ is preferably 80% or more, and more preferably 90% or more. If the purity is less than 80%, the performance of the solid electrolyte may be deteriorated.

Examples of the halogen atom for X include an iodine atom (I), a bromine atom (Br), a fluorine atom (F), a chlorine atom (Cl), and the like, and I, Br, or Cl is preferable.
As carbon number of the alkyl group of R, 1-5 are preferable.
LiX is preferably LiI, LiBr or LiCl, and more preferably LiBr.

A conventionally well-known thing can be used also about a LiX compound. The purity of LiX is preferably 80% or more, and more preferably 90% or more. If the purity is less than 80%, the performance of the solid electrolyte may be deteriorated.
A LiX compound may be used individually by 1 type, or may use 2 or more types together.

The content molar ratio of LiBH ₄ and LiX (LiBH ₄ : LiX) in the LiBH ₄ -LiX solid solution is preferably 1: 1 to 20: 1, and more preferably 1: 1 to 10: 1. If it is above the above lower limit, high ionic conductivity is likely to be obtained, and if it is below the upper limit, the transition temperature of the high temperature phase (high ionic conduction phase) tends to be lowered, so the transition temperature of the high temperature phase of LiBH ₄ ( When the temperature is lower than 115 ° C., the ionic conductivity can be sufficiently improved.

[Method for producing LiBH ₄ -LiX solid solution]
The LiBH ₄ -LiX solid solution can be produced by mixing LiBH ₄ and a LiX compound, heating the obtained mixture to melt or sinter, and then cooling, but is not particularly limited to this method. . Among these, the method of performing melt mixing is preferable in that a solid solution uniformly including LiBH ₄ and a LiX compound can be obtained.

The mixing molar ratio between LiBH ₄ and the LiX compound (LiBH ₄ : LiX compound) is preferably 1: 1 to 20: 1 and more preferably 1: 1 to 10: 1 for the same reason as described above.

  The heating temperature of the above mixture is usually 50 ° C. or higher, preferably 150 ° C. or higher, more preferably 200 ° C. or higher, particularly preferably 250 ° C. or higher, and most preferably 300 ° C. or higher. If the heating temperature is less than 50 ° C, the mixture may be insufficiently melted or sintered. In particular, the heating temperature for sintering the mixture is usually 50 to 240 ° C, preferably 150 to 240 ° C, and more preferably 200 to 240 ° C.

Moreover, it is preferable to heat the solid solution thus obtained to 115 ° C. or higher and then cool it. This tends to increase the ionic conductivity of the solid electrolyte below the transition temperature of the high temperature phase of LiBH ₄ .

The shape of the LiBH ₄ -LiX solid solution is not particularly limited, but is preferably a powder.

[Sulfide solid electrolyte and LiBH ₄ -LiX solid solution blending ratio]
The blending ratio of the sulfide solid electrolyte and the LiBH ₄ -LiX solid solution (sulfide solid electrolyte: LiBH ₄ -LiX solid solution (molar ratio)) is usually 99.9-50: 0.1-50, preferably It is 99.9-80: 0.1-20, More preferably, it is 99.9-90: 0.1-10.
If it is this range, the improvement effect of ion conductivity will be especially excellent.

In addition to the sulfide solid electrolyte and LiBH ₄ -LiX solid solution, the solid electrolyte of the present invention may optionally contain a material used for a solid electrolyte molded body to be described later.
The solid electrolyte of the present invention comprises, for example, 90% by weight or more, 95% by weight or more, 98% by weight or more, and 100% by weight of an arbitrary material used for a sulfide solid electrolyte, a LiBH ₄ -LiX solid solution, and a solid electrolyte molded body. Also good.

[Mixing method]
Mixing (compounding) of the sulfide solid electrolyte and LiBH ₄ -LiX solid solution can be carried out by dry mixing using, for example, a mortar, ball mill, bead mill, jet mill, planetary ball mill, vibration ball mill, sand mill, cutter mill, After the raw materials are dispersed in an organic solvent, wet mixing using a mortar, ball mill, bead mill, planetary ball mill, vibration ball mill, sand mill, or fill mix is performed to remove the solvent.

2. Solid Electrolyte Molded Body and Manufacturing Method Thereof The solid electrolyte molded body of the present invention is obtained by pressure molding a composition containing a sulfide solid electrolyte powder and a LiBH ₄ -LiX solid solution powder. The sulfide solid electrolyte and the LiBH ₄ -LiX solid solution are as described above.
Although only pressure molding may be used, it is preferable to include a heat treatment step. The solid electrolyte can be converted into glass ceramics by heat treatment.
In addition, the above powder can be made into a slurry by using a solvent to form a molded body, and the solvent can be removed to form a final molded body or sheet.

The molding pressure of the powder is usually 30 to 400 MPa, for example, 2 to 250 MPa.
The heat treatment temperature is usually 150 ° C to 360 ° C. If the heat treatment temperature is less than 150 ° C., it may be difficult to obtain a highly ion-conductive crystal glass, and if the heat treatment temperature exceeds 360 ° C., a crystal structure with low ion conductivity may be formed.

  The heating temperature is preferably not less than the glass transition temperature (Tg) of the solid electrolyte (glass) and not more than the crystallization temperature (Tc) of the solid electrolyte (glass) + 100 ° C. or less. If the heating temperature is lower than the Tg of the solid electrolyte (glass), the production time may be very long. On the other hand, when it exceeds (Tc + 100 ° C.), impurities or the like may be contained in the obtained solid electrolyte (glass ceramic), and the ionic conductivity may be lowered.

  The heating temperature is more preferably (Tg + 5 ° C.) or more and (Tc + 90 ° C.) or less, and further preferably (Tg + 10 ° C.) or more and (Tc + 80 ° C.) or less.

  For example, the heating temperature is 150 ° C. or higher and 360 ° C. or lower, preferably 160 ° C. or higher and 350 ° C. or lower, more preferably 180 ° C. or higher and 310 ° C. or lower, more preferably 180 ° C. or higher and 290 ° C. or lower, Especially preferably, it is 190 degreeC or more and 270 degrees C or less.

In addition, when there are two peaks by thermophysical property measurement, the temperature of the first crystallization peak on the low temperature side is Tc1, the temperature of the second crystallization peak on the high temperature side is Tc2, and heating is performed at Tc1 or more and Tc2 or less. It is preferable.
There is no specific specification for the temperature raising method. The temperature may be raised slowly to a predetermined temperature or heated rapidly.

The crystallization temperature of the glassy solid electrolyte can be specified by differential thermo-thermogravimetry or the like. For example, a thermogravimetry apparatus (TGA / DSC1 manufactured by METTLER TOLEDO) is used, and the glassy solid electrolyte is about 20 mg. Can be identified by measuring by heating at a heating rate of 10 ° C./min.
It should be noted that the crystallization temperature or the like may change depending on the temperature rising rate or the like, and should be selected based on Tc measured at a rate close to the temperature rising rate for heat treatment. Therefore, when the treatment is performed at a temperature raising rate other than the example, the optimum heat treatment temperature changes, but it is desirable to perform the heat treatment under the above-mentioned conditions with reference to Tc measured at the temperature raising rate for heat treatment.

The heating time is preferably 0.005 minutes or more and 10 hours or less. More preferably, it is 0.005 minutes or more and 5 hours or less, and particularly preferably 0.01 minutes or more and 3 hours or less.
There is no specific specification for the temperature raising method. The temperature may be raised slowly to a predetermined temperature or heated rapidly.
Heating is preferably performed in an environment with a dew point of −40 ° C. or lower, more preferably in an environment with a dew point of −60 ° C. or lower. The atmospheric pressure during heating may be a normal pressure or a reduced pressure. The atmosphere may be in the air or an inert atmosphere.

In the solid electrolyte molded body obtained by the heat treatment, the solid electrolyte powders are fused to each other. Fusion means that a part of the particulate solid electrolyte is dissolved and the dissolved part is integrated with another solid electrolyte.
The solid electrolyte molded body of the present invention that can be used for the electrolyte layer is preferably produced using a solid electrolyte having a crystal component, a glassy solid electrolyte, or a mixture thereof, and is subjected to pressure and heating to form an electrolyte. When the layer is formed, it is preferable to include a glassy solid electrolyte. Moreover, when manufacturing using the solid electrolyte which has a crystal component, Comprising: When shape | molding electrolyte by pressurizing and heating, it is preferable that the glass component is contained in the solid electrolyte which has a crystal component. The solid electrolyte layer may be a solid electrolyte plate. In addition, the case where part or all of the solid electrolyte particles are dissolved to form a plate-like body is included.

3. All-solid battery The solid electrolyte molded body of the present invention can be used for a solid electrolyte layer, a positive electrode mixture layer, and a negative electrode mixture layer of an all-solid battery such as a lithium ion secondary battery.
The solid electrolyte molded body of the present invention, depending on its use, a binder (binder), a positive electrode active material, a negative electrode active material, a conductive additive is added during production, and a positive electrode, an electrolyte layer, a negative electrode, etc. It can be used as a battery constituent material and as a member (layer) constituting the battery.

Examples of binders include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), fluorine-containing resins such as fluorine rubber; thermoplastic resins such as polypropylene and polyethylene; ethylene-propylene-diene rubber (EPDM), sulfonated EPDM, natural Butyl rubber (NBR) or the like can be used alone or as a mixture of two or more.
In addition, an aqueous binder such as a cellulose binder or an aqueous dispersion of styrene butadiene rubber (SBR) can also be used.

As the positive electrode active material, a material capable of inserting and desorbing lithium ions, and a material known as a positive electrode active material in the battery field can be used.
For example, V ₂ O ₅ , LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , Li (Ni _a Co _b Mn _c ) O ₂ (where 0 <a <1, 0 <b <1, 0 < c <1, a + b + c = 1), LiNi _0.8 Co _0.15 Al _0.05 O ₂ , LiNi _1-Y Co _Y O 2, LiCo _1-Y Mn _{Y 2} O ₂ , LiNi _1-Y Mn _{Y 2} O ₂ ( Here, 0 ≦ Y <1), Li (Ni _a Co _b Mn _c ) O ₄ (0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn _2−Z NiZO ₄ , LiMn ₂ -Z Co _Z O ₄ (where 0 <Z <2), LiCoPO ₄ , LiFePO ₄ , bismuth oxide (Bi ₂ O ₃ ), bismuth leadate (Bi ₂ Pb ₂ O ₅ ), copper oxide (CuO), vanadium oxide (V ₆ O ₁₃ Li _x CoO ₂ , Li _x NiO ₂ , Li _x Mn ₂ O ₄ , Li _x FePO ₄ , Li _x CoPO ₄ , Li _x Mn _1/3 Ni _1/3 Co _1/3 O ₂ , Li _x Mn _{1 And} oxides such as _0.5 Ni _0.5 O ₂ . Other positive electrode active materials include, for example, elemental sulfur (S), titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), iron sulfide (FeS, FeS ₂ ), copper sulfide (CuS) in the sulfide system. And nickel sulfide (Ni ₃ S ₂ ), lithium sulfide (Li ₂ S), organic disulfide compounds, carbon sulfide compounds, sulfur, and the like can be used. Preferably, S and Li ₂ S having a high theoretical capacity can be used.

（式（Ａ）〜（Ｃ）において、Ｘはそれぞれ置換基であり、ｎ及びｍはそれぞれ独立に１〜２の整数であり、ｐ及びｑはそれぞれ独立に１〜４の整数である。
式（Ｄ）において、Ｚはそれぞれ−Ｓ−又は−ＮＨ−であり、ｎは繰返数２〜３００の整数である。）

（式中、ｎ及びｍはそれぞれ独立の整数である。） The organic disulfide compound and the carbon sulfide compound are exemplified below.

(In Formulas (A) to (C), X is a substituent, n and m are each independently an integer of 1 to 2, and p and q are each independently an integer of 1 to 4.
In formula (D), Z is -S- or -NH-, respectively, and n is an integer of 2 to 300 repetitions. )

(In the formula, n and m are independent integers.)

Examples of the shape of the positive electrode active material include a particle shape, and a true spherical shape or an elliptical spherical shape is preferable.
When the positive electrode active material is in the form of particles, the average particle size is preferably in the range of 0.1 to 100 μm, more preferably in the range of 1 to 50 μm, and particularly preferably in the range of 1 to 25 μm. is there. When the average particle diameter of the positive electrode active material particles deviates from the above range, a dense positive electrode active material layer may not be obtained.

As the negative electrode active material, a material capable of inserting and desorbing lithium ions, and a material known as a negative electrode active material in the battery field can be used.
For example, carbon materials, specifically artificial graphite, graphite carbon fiber, resin-fired carbon, pyrolytic vapor-grown carbon, coke, mesocarbon microbeads (MCMB), furfuryl alcohol resin-fired carbon, polyacene, pitch-based carbon Examples thereof include fibers, vapor-grown carbon fibers, natural graphite, and non-graphitizable carbon, and a mixture thereof may be used. Preferably, it is artificial graphite.
In addition, an alloy combined with a metal itself such as metallic lithium, metallic indium, metallic aluminum, metallic silicon, or another element or compound can be used as the negative electrode material. Among these, silicon, tin, and lithium metal having a high theoretical capacity are preferable.

The conductive auxiliary agent only needs to have conductivity, and the conductivity of the conductive auxiliary agent is preferably 1 × 10 ³ S / cm or more, more preferably 1 × 10 ⁵ S / cm or more. .
Examples of the conductive assistant include substances selected from carbon materials, metal powders and metal compounds, and mixtures thereof.
Specific examples of conductive aids are preferably carbon, nickel, copper, aluminum, indium, silver, cobalt, magnesium, lithium, chromium, gold, ruthenium, platinum, beryllium, iridium, molybdenum, niobium, osnium, rhodium, tungsten And a substance containing at least one element selected from the group consisting of zinc, more preferably simple carbon, carbon, nickel, copper, silver, cobalt, magnesium, lithium, ruthenium, gold, platinum, niobium, osnium or rhodium A simple metal, a mixture or a compound containing
In particular, specific examples of the carbon material for the conductive assistant include carbon black such as ketjen black, acetylene black, denka black, thermal black, and channel black, graphite, carbon fiber, activated carbon, and the like. These can be used alone or in combination of two or more.
Among the above conductive assistants, acetylene black, denka black, and ketjen black having high electron conductivity are preferable.

The electrolyte layer (sheet) is made of the solid electrolyte molded body of the present invention.
The electrolyte layer may be composed of a solid electrolyte molded body and other electrolytes depending on the purpose of use. The thickness of the electrolyte layer is preferably 0.001 mm or more and 1 mm or less.

The other electrolyte is, for example, a polymer solid electrolyte or an oxide solid electrolyte.
The polymer-based solid electrolyte is not particularly limited. For example, as disclosed in JP 2010-262860 A, materials used as a polymer electrolyte such as a fluororesin, polyethylene oxide, polyacrylonitrile, polyacrylate, derivatives thereof, and copolymers thereof can be used.

  As a fluororesin, what contains vinylidene fluoride (VdF), hexafluoropropylene (HFP), tetrafluoroethylene (TFE), these derivatives, etc. as a structural unit is mentioned, for example. Specifically, a homopolymer such as polyvinylidene fluoride (PVdF), polyhexafluoropropylene (PHFP), polytetrafluoroethylene (PTFE), or a copolymer of VdF and HFP (hereinafter, this copolymer is referred to as “ P (VdF-HFP) ”may be used, and binary copolymers and ternary copolymers.

Examples of the oxide-based solid electrolyte include crystals having a perovskite structure such as LiN, LISICON, La _0.55 Li _0.35 TiO ₃ , LiTi ₂ P ₃ O ₁₂ having a NASICON type structure, and further crystallizing these. An electrolyte or the like can be used.

The positive electrode layer preferably contains a positive electrode active material, an electrolyte, and a conductive additive. Moreover, the binder may be included.
In the positive electrode layer, the ratios of the positive electrode active material, the electrolyte, the conductive auxiliary agent and the like are not particularly limited, and known ratios can be used.
The thickness of the positive electrode layer is preferably 0.01 mm or more and 10 mm or less.
The positive electrode layer can be produced by a known method. For example, it can be produced by a coating method or an electrostatic method (electrostatic spray method, electrostatic screen method, etc.).

It is preferable that a negative electrode layer contains a negative electrode active material, an electrolyte, and a conductive support agent. Moreover, the binder may be included.
The thickness of the negative electrode layer is preferably 0.01 mm or more and 10 mm or less.
The negative electrode layer can be produced by a known method. For example, it can be produced by a coating method or an electrostatic method (electrostatic spray method, electrostatic screen method, etc.).

  The battery of the present invention preferably uses a current collector in addition to the positive electrode layer, the electrolyte layer, and the negative electrode layer. A known current collector can be used. For example, a layer coated with Au or the like that reacts with a sulfide-based solid electrolyte such as Au, Pt, Al, Ti, or Cu can be used.

The all solid state battery is preferably an all solid state battery in which at least one of the positive electrode layer, the electrolyte layer, and the negative electrode layer is made of the solid electrolyte molded body of the present invention.
In this embodiment, it is sufficient that at least one of the positive electrode layer, the electrolyte layer, and the negative electrode layer is made of the solid electrolyte molded body of the present invention.

FIG. 1 is a schematic cross-sectional view showing an embodiment of an all-solid battery.
In the all solid state battery 100, the solid electrolyte molded body 120 of the present invention is sandwiched between a pair of electrodes including a positive electrode 110 and a negative electrode 130. Current collectors 140 and 142 are provided on the positive electrode 110 and the negative electrode 130, respectively.

The negative electrode 130 is a negative electrode made of a negative electrode active material, preferably a heat treatment of a negative electrode mixture containing sulfide-based electrolyte powder. In the negative electrode mixture, the mixing ratio (weight ratio) between the sulfide-based electrolyte powder and the negative electrode material is preferably sulfide-based electrolyte powder: negative electrode active material = 20-50: 80-50.
In order to allow electrons to move smoothly in the positive electrode active material, the above-described conductive aid may be added to the positive electrode 110 and the negative electrode 130 as appropriate.

The positive electrode and the negative electrode can be produced by forming the electrode material in a film shape on at least a part of the current collector. Examples of the film forming method include a blast method, an aerosol deposition method, a cold spray method, a sputtering method, a vapor phase growth method, and a thermal spraying method. By forming a film by such a method, the porosity of the electrode material layer can be further reduced, and the ionic conductivity can be improved.
Blasting and aerosol deposition are preferred because they can be formed in a temperature range that does not change the crystal state of the electrolyte under simple equipment and room temperature conditions.

  Examples of the current collectors 140 and 142 include copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, indium, lithium, or a plate or foil made of these alloys. Can be used.

  An all-solid-state battery can be manufactured by bonding and joining the battery members described above. As a method of joining, there are a method of laminating each member, pressurizing and pressure bonding, a method of pressing through two rolls (roll to roll), and the like. You may join to a joint surface through the active material which has ion conductivity, and the adhesive material which does not inhibit ion conductivity. In joining, heat fusion may be performed as long as the crystal structure of the solid electrolyte does not change.

  Moreover, it is preferable that the all solid state battery manufactured by the above method is further heat-treated. The heating conditions are usually 100 to 350 ° C. and 0.1 to 10 hours. A battery with high output can be produced by heating. The heat treatment of the all-solid battery includes a case where only the battery element portion including only the negative electrode, the solid electrolyte formed body, and the positive electrode is heat-treated. Also, it does not include heat treatment such as safety devices and lapping.

Hereinafter, the present invention will be described in more detail with reference to examples.
In the following examples, the ionic conductivity (σ) was evaluated as follows.
The sample is molded into a cylindrical shape having a cross-sectional diameter of 10 mm (cross-sectional area S = 0.785 cm ² ) and a height of 0.1-0.3 cm to obtain a sample piece. Take electrode terminals from above and below the specimen. Measurement is performed by the AC impedance method (frequency range: 5 MHz to 0.5 Hz, amplitude: 10 mV), and a Cole-Cole plot is obtained. In the vicinity of the right end of the arc observed in the high-frequency region, the real part Z ′ (Ω) at the point where −Z ″ (Ω) is the minimum is the bulk resistance R (Ω) of the electrolyte. The conductivity σ (S / cm) is calculated. In addition, the distance of the lead was measured at about 60 cm.
R = ρ (L / S)
σ = 1 / ρ

Production Example 1
[Production of lithium sulfide (NMP method)]
(1) Production of lithium sulfide A 10-liter autoclave equipped with a stirring blade was charged with 3326.4 g (33.6 mol) of N-methyl-2-pyrrolidone (NMP) and 287.4 g (12 mol) of anhydrous lithium hydroxide. The temperature was raised to 130 ° C. at 300 rpm. After the temperature increase, hydrogen sulfide was blown into the liquid for 2 hours at a supply rate of 3 L / min.
Subsequently, the temperature of the reaction solution was raised under a nitrogen stream (200 cc / min), and the produced lithium hydrosulfide was desulfurized to obtain lithium sulfide. As the temperature increased, water produced as a by-product due to the reaction between hydrogen sulfide and lithium hydroxide began to evaporate, and this water was condensed by a condenser and extracted out of the system. Water was distilled out of the system and the temperature of the reaction solution rose. When the temperature reached 180 ° C., the temperature increase was stopped and the temperature was kept constant. After the dehydrosulfurization reaction of lithium hydrosulfide (about 80 minutes) was completed, the reaction was terminated to obtain lithium sulfide.

(2) Purification of lithium sulfide After decanting NMP in the 500 mL slurry reaction solution (NMP-lithium sulfide slurry) obtained in (1), 100 mL of dehydrated NMP was added and stirred at 105 ° C. for about 1 hour. NMP was decanted at that temperature. The same operation was repeated 4 times in total. After completion of the decantation, 100 mL of dehydrated heptane was added, and the mixture was stirred at room temperature to remove the supernatant. This operation was repeated 5 times. The heptane slurry was collected and filtered under a nitrogen stream to remove the solvent. Vacuum drying was performed at 200 ° C. to obtain purified lithium sulfide.
The purity of the obtained purified lithium sulfide was calculated by potentiometric titration to be 98.9% by weight.
When the BET specific surface area (krypton method) was evaluated, the specific surface area was 0.04 m ² / g and the pore volume was 0.001 ml / g or less.

Production Example 2
[Production of sulfide solid electrolyte glass (Li ₂ S / P ₂ S ₅ /LiBr=75/25/16.8 (MM method))]
0.337 g (0.00717 mol) of lithium sulfide obtained in Production Example 1, 0.532 g (0.00239 mol) of nilin pentasulfide (manufactured by Aldrich), and 0.140 g (0.003 mol) of lithium bromide (manufactured by Aldrich). 00161 mol) was mixed well. The mixed powder and 10 zirconia balls having a diameter of 10 mm are put into a planetary ball mill (Fritche: Model No. P-7) alumina pot and completely sealed, and the alumina pot is filled with nitrogen. The atmosphere.
During the first few minutes, the planetary ball mill was rotated at a low speed (100 rpm), and then the planetary ball mill was gradually increased to 370 rpm. Mechanical milling was performed at a rotational speed of 370 rpm for 20 hours.
As a result of XRD measurement (CuKα: λ = 1.5405Å), the characteristic peak derived from the raw material disappeared, and it was confirmed that the raw material had reacted.

Production Example 3
[Production of sulfide solid electrolyte glass ceramics (Li ₂ S / P ₂ S ₅ /LiBr=75/25/16.8)]
The sulfide glass produced in the same manner as in Production Example 2 was heat-treated at 220 ° C. for 2 hours in an argon atmosphere to obtain sulfide glass ceramic powder. The ionic conductivity of the sulfide glass ceramic powder was 1.0 × 10 ⁻³ S / cm.

Production Example 4
[Production of LiBH ₄ -LiBr solid solution]
According to Patent Document 4, LiBH ₄ (manufactured by Aldrich, purity 90%) and LiBr (manufactured by Aldrich, purity 99.99%) were mixed at a molar ratio of LiBH ₄ : LiBr = 3: 1. After the mixture was transferred to a glass cell, it was heated to 320 ° C. and melt mixed. Thereafter, this molten mixture was cooled to room temperature to obtain a LiBH ₄ -LiBr solid solution. As a result of performing X-ray diffraction measurement (XRD), the position of the obtained peak was shifted from the position of the LiBH ₄ peak, so that it was confirmed that it was dissolved. The absence of unreacted raw material was confirmed from the disappearance of the XRD peak of the raw material.
When the obtained LiBH ₄ -LiBr solid solution was subjected to XRD measurement (CuKα: λ = 1.5405Å), the same characteristic peak as in Patent Document 4 was observed.
This LiBH ₄ -LiBr solid solution was sufficiently pulverized in a mortar and subjected to the next step.

Example 1
[Manufacture of solid electrolyte powder]
The sulfide solid electrolyte glass ceramic powder obtained in Production Example 3 and the LiBH ₄ -LiBr solid solution powder obtained in Production Example 4 were blended in a molar ratio of 90:10 to obtain a solid electrolyte. Powdered.
This solid electrolyte powder was filled in a tablet molding machine, and a pressure of 185 MPa was applied to obtain a solid electrolyte sheet. The thickness was 1.5 mm.
The ionic conductivity of this solid electrolyte sheet was 3.0 × 10 ⁻³ S / cm.

Example 2
[Manufacture of solid electrolyte powder]
The powder of the sulfide solid electrolyte glass obtained in Production Example 2 and the powder of the LiBH ₄ -LiBr solid solution obtained in Production Example 4 were blended in a molar ratio of 90:10 to obtain a solid electrolyte powder. The body.
This solid electrolyte powder was filled in a tablet molding machine, and a pressure of 185 MPa was applied to obtain a solid electrolyte sheet. The thickness was 1.5 mm. This solid electrolyte sheet was put in a glass bottle, further sealed in a SUS tube in an argon atmosphere, and heat-treated at 220 ° C. for 2 hours.
The ionic conductivity of this solid electrolyte sheet was 4.0 × 10 ⁻³ S / cm.

Comparative Example 1
As Comparative Example 1, the glass ceramic of Production Example 3, which is a solid electrolyte not including a LiBH ₄ —LiX solid solution, was employed. The ionic conductivity of this glass ceramic was 1.0 × 10 ⁻³ S / cm.

  The solid electrolyte of the present invention can be used for a lithium ion secondary battery used in a portable information terminal, a portable electronic device, a small household electric power storage device, a motorcycle using a motor as a power source, an electric vehicle, a hybrid electric vehicle, and the like.

DESCRIPTION OF SYMBOLS 100 All-solid-state battery 110 Positive electrode layer 120 Solid electrolyte layer 130 Negative electrode layer 140,142 Current collector

Claims (6)

A sulfide solid electrolyte,
LiBH ₄ in which LiX is dissolved,
Containing solid electrolyte.
(In the formula, X represents a halogen atom, —NR ₂ or —N ₂ R. R represents a hydrogen atom or an alkyl group, respectively.) The solid electrolyte according to claim 1, wherein the sulfide solid electrolyte and LiBH ₄ in which LiX is dissolved are powders. The sulfide solid electrolyte is
A solid electrolyte obtained from Li ₂ S and P ₂ S ₅ ;
A solid electrolyte obtained from Li ₂ S, GeS ₂ and P ₂ S ₅ ;
The solid electrolyte according to claim 1, which is one or more solid electrolytes selected from a solid electrolyte obtained from Li ₂ S, P ₂ S ₅ and LiX ′, and an aldilodite Li ₆ PS ₅ X ′ solid electrolyte. (In the formula, X ′ represents a halogen atom.)   The solid electrolyte molded object formed by pressure-molding the solid electrolyte in any one of Claims 1-3.   An all-solid battery comprising the solid electrolyte molded body according to claim 4. Manufacture of a solid electrolyte molded body including a step of pressure-molding a composition comprising a sulfide solid electrolyte powder and a LiBH ₄ powder in which LiX is dissolved, and a step of heat-treating the obtained molded body Method.

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