JP6131851B2 - Method for producing sulfide solid electrolyte material - Google Patents

Description

  The present invention relates to a sulfide solid electrolyte material having high Li ion conductivity.

  In recent years, a secondary battery has become an indispensable component as a power source for personal computers, video cameras, mobile phones, and the like, or as a power source for automobiles and power storage.

  Among secondary batteries, a lithium ion secondary battery or a lithium secondary battery has a feature that it has a higher capacity density than other secondary batteries and can operate at a high voltage. Therefore, it is used in information-related equipment and communication equipment as secondary batteries that are easy to reduce in size and weight. In recent years, high-output and high-capacity lithium-ion secondary batteries for electric vehicles and hybrid vehicles as low-pollution vehicles have been used. Development is underway.

  A lithium ion secondary battery or a lithium secondary battery includes a positive electrode layer and a negative electrode layer, and an electrolyte containing a lithium salt disposed between the positive electrode layer and the negative electrode layer, and the electrolyte is constituted by a non-aqueous liquid or solid. . When a non-aqueous liquid electrolyte is used for the electrolyte, the electrolyte solution penetrates into the positive electrode layer, so that an interface between the positive electrode active material constituting the positive electrode layer and the electrolyte is easily formed, and performance is easily improved. . However, since widely used electrolytes are flammable, it is necessary to install a system for ensuring safety such as attachment of a safety device that suppresses temperature rise at the time of short circuit and prevention of short circuit. In contrast, an all-solid battery in which the liquid electrolyte is changed to a solid electrolyte layer to make the battery all solid does not use a flammable organic solvent in the battery, so the safety device can be simplified and the manufacturing cost and production can be simplified. It is thought that it is excellent in performance, and development is underway.

A sulfide solid electrolyte material is known as a solid electrolyte material used for such a solid electrolyte layer. Since the sulfide solid electrolyte material has high Li ion conductivity, it is useful for increasing the output of the battery, and various studies have been made heretofore. For example, Patent Document 1 describes that LiI—Li ₂ S—P ₂ S ₅ -based sulfide glass is heat-treated to obtain glass ceramics.

JP 2013-016423 A

Although the glass ceramic obtained by heat-treating the LiI—Li ₂ S—P ₂ S ₅ sulfide glass obtained in Patent Document 1 has a predetermined Li ion conductivity, it is still improved Li ions. A sulfide solid electrolyte material having conductivity is desired.

The present _{invention, LiI-LiX-Li 2 S} -P 2 S 5 sulfide solid electrolyte (wherein, X is Cl, F or Br,) a process for the preparation of,
Amorphizing a raw material composition containing LiI, LiX (wherein X is Cl, F, or Br), Li ₂ S, and P ₂ S ₅ to obtain a sulfide glass;
Heat treating the sulfide glass at the nucleation temperature of the sulfide glass, and heat treating the heat treated sulfide glass at the crystal growth temperature of the sulfide glass;
It is a manufacturing method containing.

  According to the present invention, a sulfide solid electrolyte material having a higher Li ion conductivity than before can be obtained.

FIG. 1 is an example of a two-stage heat treatment profile in the method according to the present invention. FIG. 2 shows the DTA analysis results of the sulfide glasses obtained in the examples and comparative examples. FIG. 3 shows the Li ion conductivity of the sulfide solid electrolyte materials obtained in the examples and comparative examples. FIG. 4 is a powder X-ray diffraction profile of the sulfide solid electrolyte material obtained in Examples and Comparative Examples. FIG. 5 is a schematic cross-sectional view of an all-solid battery that can be manufactured using a sulfide solid electrolyte material obtained by the method according to the present invention. FIG. 6 is a powder X-ray diffraction profile of sulfide glass synthesized by amorphizing the raw material composition.

Conventionally, LiI—Li ₂ S—P ₂ S ₅ glass, which is a sulfide solid electrolyte, is known as a material excellent in Li ion conductivity, but it has been difficult to improve Li ion conductivity beyond this.

Accordingly, the present inventors have revealed that an extensive investigation for the purpose of further improving the Li-ion conductivity, the _{LiI-Li 2 S-P 2} S 5 glass, there is high Li ion conductive phase and low Li-ion conducting phase I understood that. Then, in the differential thermal analysis performed on _{LiI-Li 2 S-P 2} S 5 amorphous glass, small exothermic peaks present in the high temperature side than the exothermic peak of the high Li ion conductive phase is, high Li ion conductive phase It has been found that this is an exothermic peak of a low Li ion conducting phase with lower Li ion conductivity.

  The generation temperature range of both the high Li ion conduction phase and the low Li ion conduction phase is close, and the generation temperature range of the low Li ion conduction phase is wide. It has been difficult to increase the crystallinity of the Li ion conducting phase.

  In contrast, by intensively studying the composition of the sulfide solid electrolyte and shifting the generation temperature range of the low Li ion conduction phase to the high temperature side, while reducing or suppressing the generation of the low Li ion conduction phase, the high Li Li It has been found that the crystallinity of the ion conduction phase can be increased. Thereby, it turned out that the crystallinity of a high Li ion conduction phase can be improved, suppressing the production | generation of a low Li ion conduction phase.

  Further, by shifting the exothermic peak of the low Li ion conducting phase to the high temperature side, the endothermic peak of the glass transition point (Tg) immediately before the exothermic peak of the high Li ion conducting phase (crystallization temperature of the high Li ion conducting phase). By carrying out a heat treatment in the vicinity of the glass transition point (Tg), and then performing a two-step heat treatment in which the temperature is raised to the crystal growth temperature of the high Li ion conduction phase, It was found that the crystallinity of the conductive phase can be further improved and the Li ion conductivity can be further improved. In the composition in which the glass transition point (Tg) is not observed, the effect of improving the crystallinity of the high Li ion conduction phase cannot be obtained even if the same two-step heat treatment is performed.

That is, the present invention is a method for producing a LiI—LiX—Li ₂ S—P ₂ S ₅ sulfide solid electrolyte material (wherein X is Cl, F, or Br), which comprises LiI, LiX (formula Wherein X is Cl, F, or Br), a raw material composition containing Li ₂ S, and P ₂ S ₅ is amorphized to obtain a sulfide glass, and at the nucleation temperature of the sulfide glass, The present invention is directed to a manufacturing method including heat-treating sulfide glass and heat-treating the heat-treated sulfide glass at a crystal growth temperature of sulfide glass.

FIG. 1 shows an example of a two-stage heat treatment profile in the method according to the present invention. In FIG. 1, the temperature is raised to the nucleation temperature that is the first temperature T ₁ and held for a predetermined time, and then the temperature is raised to the crystal growth temperature that is the second temperature T ₂ and held for a predetermined time. The cooling profile is shown.

In the production method according to the present invention, a raw material composition containing LiI, LiX (wherein X is Cl, F, or Br), Li ₂ S, and P ₂ S ₅ is used.

ALiX · (100-a) (0.75Li ₂ S · 0.25P ₂ S ₅ ) glass (X is I, Cl, F, or Br) such as conventional LiI—Li ₂ S—P ₂ S ₅ glass Although it is known as a material excellent in Li ion conductivity, as described above, the present inventor considered that aLiX. (100-a) (0.75Li ₂ S.0.25P ₂ S ₅ ) glass has In addition to the high Li ion conduction phase, the low Li ion conduction phase is also included, and both the high Li ion conduction phase and the low Li ion conduction phase are generated at almost the same temperature range, thus further improving the Li ion conductivity. I found out that it was difficult.

Then, by adding LiX (wherein X is Cl, F, or Br) to the LiI—Li ₂ S—P ₂ S ₅ series material, the temperature range in which the low Li ion conduction phase is generated is increased to the high temperature side. It has been found that it can be shifted, thereby reducing the amount of low Li ion conducting phase produced, or producing only a high Li ion conducting phase without producing a low Li ion conducting phase.

  Further, by shifting the temperature range where the low Li ion conduction phase is generated to the high temperature side, the glass transition point (Tg) on the low temperature side of the exothermic peak of the high Li ion conduction phase (crystallization temperature of the high Li ion conduction phase). An endothermic peak was observed. The crystallinity of the high Li ion conduction phase can be further improved by performing a heat treatment near the glass transition point (Tg) and then raising the temperature to the crystallization temperature of the high Li ion conduction phase. It was found that the Li ion conductivity can be further improved.

  In a composition system in which a glass transition point is observed, when a heat treatment is performed near the glass transition point (Tg), crystal nuclei are formed, and then heat treatment at a crystal growth temperature higher than that promotes crystal growth. It is thought that the property can be improved. Thus, by performing multi-stage firing on a composition system in which a glass transition point is observed, crystallinity can be improved and lithium ion conductivity can be improved.

  As described above, the temperature range where the low Li ion conduction phase is generated is shifted to the high temperature side, and the difference from the temperature range where the high Li ion conduction phase is generated is to be analyzed by X-ray diffraction measurement and differential thermal analysis. Using the result, it can also be expressed as follows.

Sulfide glass obtained by amorphizing a raw material containing LiI, Li ₂ S, P ₂ S ₅ , and LiX (wherein X is Cl, F, or Br) used in the method according to the present invention. Is heat-treated, a high Li ion conducting phase having peaks at 2θ = 20.2 ° and 23.6 ° and peaks at 2θ = 21.0 ° and 28.0 ° in X-ray diffraction measurement using CuKα rays It can have a low Li ion conducting phase. In the present specification, a high Li ion conducting phase having peaks at 2θ = 20.2 ° and 23.6 ° is c1, and a low Li ion conducting phase having peaks at 2θ = 21.0 ° and 28.0 °. Is called cx, and the temperature of the exothermic peak of c1 in the differential thermal analysis is also called T _c1 , and the temperature of the exothermic peak of _cx is also called T _cx .

In the method according to the present invention, a sulfide glass obtained by amorphizing a raw material containing LiI, Li ₂ S, P ₂ S ₅ , and LiX (wherein X is Cl, F, or Br) When differential thermal analysis was performed, T _cx was found on the higher temperature side than LiI-Li ₂ S—P ₂ S ₅ glass, and a result of a large temperature difference between T _cx and T _c1 was obtained.

The temperature difference between T _c1 and T _cx of the sulfide glass produced in the method according to the present invention is preferably T _cx −T _c1 ≧ 55 ° C., more preferably T _cx −T _c1 ≧ 60 ° C., and more preferably T _cx. −T _c1 ≧ 65 ° C., even more preferably T _cx −T _c1 ≧ 70 ° C. When the temperature difference between T _cx and T _c1 satisfies the above range, a sulfide solid electrolyte material with higher Li ion conductivity can be obtained.

The values of T _c1 , T _cx , and T _g depend on the composition of the sulfide glass containing LiI, Li ₂ S, P ₂ S ₅ , and LiX (where X is Cl, F, or Br). Although the value of T _c1 is about 170 ° C. to 200 ° C., T _g is a temperature range near the low temperature side of T _c1 , for example, 150 to 170 ° C., and T _cx is, for example, 230 ° C. or more. Is preferable, and it is more preferable that it is 260 degreeC or more.

Differential thermal analysis can be performed using a TG-DTA apparatus. T _c1 , T _cx , and T _c2 can be detected as the temperature of the peak top, and T _g is detected as the temperature of the intersection of the background on the low temperature side of T _c1 and the tangent at the inflection point of the endothermic peak. Can do. The inflection point is a point where an upward convex curve changes to a downward convex curve.

In the raw material composition used in the present invention, the ratio of the total amount of LiI and LiX (wherein X is Cl, F, or Br) is preferably 10 mol% to 30 mol% with respect to the entire raw material composition. More preferably, it is in the range of 15 mol% to 25 mol%. When the ratio of the total amount of LiI and LiX is within the above range, the temperature difference between T _c1 and T _cx can be further increased, the formation of a low Li ion conduction phase is further suppressed, and the Li ion conductivity is increased. Can be made higher.

In the raw material composition used in the present invention, the ratio of LiX to the total of LiI and LiX (where X is Cl, F, or Br) (LiX / (LiI + LiX)) is not particularly limited. Is preferably in the range of 1 mol% to 99 mol%, more preferably in the range of 5 mol% to 75 mol%, and still more preferably in the range of 25 mol% to 50 mol%. When the ratio of LiX is within the above range, the difference between T _cx and T _c1 can be further increased. The mechanism is not necessarily clear, but it is presumed that it became difficult to conform to the crystal structure of the low Li ion conduction phase by substituting a part of I with Cl, F, or Br having a small ionic radius. The

  In the present invention, LiX is preferably LiBr, but may be LiCl or LiF. When LiX is LiBr, the endothermic peak at the glass transition point Tg can be detected more clearly by differential thermal analysis, and higher Li ion conductivity can be obtained.

The ratio of Li ₂ S to the total of Li ₂ S and P ₂ S ₅ (Li ₂ S / (Li ₂ S + P ₂ S ₅ )) is preferably in the range of 75 mol% to 79 mol%, more preferably 76 mol% to 78 mol. %. When the ratio of Li ₂ S is within the above range, the difference between T _cx and T _c1 can be further increased. The mechanism is not necessarily clear, but Li ₂ S has a slightly surplus composition with respect to the PS ₄ unit, resulting in an interaction between LiI and Li ₂ S, realizing a crystal structure of a low Li ion conducting phase. It is presumed that it was difficult to do.

The sulfide solid electrolyte material obtained by the method according to the present invention includes a (LiI · LiX) · (1-a) (bLi ₂ S · (1-b) P ₂ S ₅ ) (wherein X is Cl, F or Br). a corresponds to the ratio of the total amount of LiI and LiX, and b corresponds to the ratio of Li ₂ S.

If the exothermic peak of T _cx is shifted to the high temperature side, it may overlap with the exothermic peak of the β-Li ₃ PS ₄ crystal phase. In the present specification, the temperature of the exothermic peak of the β-Li ₃ PS ₄ crystal phase is also referred to as T _c2 . In the present invention, when the exothermic peak of T _{cx and} the exothermic peak of T _c2 overlap, T _c2 can be approximately used as T _cx . In this case, for example, the value of T _cx −T _c1 can be approximated as the value of T _c2 −T _c1 .

(Amorphization process)
The method according to the present invention includes amorphizing a raw material composition containing LiI, LiX (wherein X is Cl, F, or Br), Li ₂ S, and P ₂ S ₅ . In the amorphization step of the present invention, the raw material composition containing Li ₂ S, P ₂ S ₅ , LiI, and LiX (wherein X is Cl, F, or Br) is amorphized and sulfided. This is a process for obtaining a physical glass.

In this specification, the sulfide glass refers to a material synthesized by amorphizing a raw material composition, and only a strict “glass” in which periodicity as a crystal is not observed in powder X-ray diffraction (XRD) measurement or the like. In other words, it means all materials synthesized by amorphization by mechanical milling described later. Therefore, the sulfide glass obtained by amorphizing the raw material composition preferably has no peak derived from the raw material (LiI or the like) in powder X-ray diffraction measurement or the like, but the peak derived from the raw material is one. Even if a part is observed, it is sufficient that the whole is amorphous. FIG. 6 shows an example of a powder X-ray diffraction profile of sulfide glass synthesized by amorphizing the raw material composition. The composition A in FIG. 6 is a sulfide glass obtained by amorphization using LiI, LiBr, Li ₂ S, and P ₂ S ₅ as a raw material composition, and the composition B has LiI, Li ₂ S, and This is a sulfide glass obtained by amorphizing P ₂ S ₅ as a raw material composition. If no clear crystal peak is observed in the profile as shown in FIG. 6, it can be determined that the whole is amorphous.

  Examples of the method for amorphizing the raw material composition include mechanical milling and melt quenching, and mechanical milling is more preferable. This is because mechanical milling can be performed at room temperature, and the manufacturing process can be simplified. Although the melting and quenching method has limitations on the reaction atmosphere and reaction vessel, mechanical milling has an advantage that a sulfide glass having a desired composition can be easily synthesized. The mechanical milling may be dry mechanical milling or wet mechanical milling, but wet mechanical milling is preferable. This is because wet mechanical milling can prevent the raw material composition from adhering to the wall surface of a container or the like, and a sulfide glass with higher amorphousness can be obtained.

  Mechanical milling is not particularly limited as long as the raw material composition is mixed while applying mechanical energy, and examples thereof include a ball mill, a vibration mill, a turbo mill, a mechanofusion, and a disk mill. A ball mill is more preferable, and a planetary ball mill is more preferable. This is because the desired sulfide glass can be efficiently obtained by these mechanical milling.

  Various conditions of mechanical milling can be set so that a desired sulfide glass can be obtained. For example, when a planetary ball mill is used, the raw material composition and grinding balls are added to the container, and the treatment is performed at a predetermined rotation speed and time. In general, the larger the number of revolutions, the faster the generation rate of sulfide glass, and the longer the treatment time, the higher the conversion rate from the raw material composition to sulfide glass.

  The rotation speed of the base plate when performing the planetary ball mill is, for example, in the range of 200 rpm to 500 rpm, and preferably in the range of 250 rpm to 400 rpm. Moreover, the processing time when performing the planetary ball mill is, for example, in the range of 1 hour to 100 hours, and preferably in the range of 1 hour to 50 hours.

Examples of the material for the container and ball for grinding used in the ball mill include ZrO ₂ and Al ₂ O ₃ . The particle diameter of the grinding balls is, for example, in the range of 1 mm to 20 mm.

  The liquid used for wet mechanical milling preferably has a property that does not generate hydrogen sulfide by reaction with the raw material composition. Hydrogen sulfide is generated when protons dissociated from liquid molecules react with the raw material composition or sulfide glass. Therefore, it is preferable that the liquid has an aprotic property that does not generate hydrogen sulfide. In addition, aprotic liquids can be broadly classified into polar aprotic liquids and nonpolar aprotic liquids.

  Although it does not specifically limit as a polar aprotic liquid, For example, Ketones, such as acetone; Nitriles, such as acetonitrile; Amides, such as N, N- dimethylformamide (DMF); Dimethyl sulfoxide (DMSO) And the like.

  An example of a nonpolar aprotic liquid is alkane that is liquid at room temperature (25 ° C.). The alkane may be a chain alkane or a cyclic alkane. The chain alkane preferably has, for example, 5 or more carbon atoms. On the other hand, the upper limit of the carbon number of the chain alkane is not particularly limited as long as it is liquid at room temperature. Specific examples of the chain alkane include pentane, hexane, heptane, octane, nonane, decane, undecane, dodecane, and paraffin. The chain alkane may have a branch. On the other hand, specific examples of the cyclic alkane include cyclopentane, cyclohexane, cycloheptane, cyclooctane, and cycloparaffin.

  Other examples of nonpolar aprotic liquids include aromatic hydrocarbons such as benzene, toluene and xylene; chain ethers such as diethyl ether and dimethyl ether; cyclic ethers such as tetrohydrofuran; chloroform Alkyl halides such as methyl chloride and methylene chloride; esters such as ethyl acetate; fluorinated benzene, heptane fluoride, 2,3-dihydroperfluoropentane, 1,1,2,2,3,3 Fluorine compounds such as 4-heptafluorocyclopentane can be exemplified. In addition, the addition amount of the said liquid is not specifically limited, What is necessary is just the quantity which can obtain a desired sulfide solid electrolyte material.

(Heat treatment process at nucleation temperature)
According to the method of the present invention, a sulfide glass obtained by amorphizing a raw material composition containing LiI, LiX (wherein X is Cl, F, or Br), Li ₂ S, and P ₂ S ₅ is used. Heat treatment at the nucleation temperature. The heat treatment of the amorphized sulfide glass at the nucleation temperature is performed by heat-treating the amorphized sulfide glass near the glass transition point (Tg). The heat treatment at the nucleation temperature is preferably performed by heat-treating the amorphized sulfide glass at a first temperature T ₁ in the range of ± 20 ° C. of the glass transition point Tg.

The lower limit of the first temperature T ₁ is more preferably Tg-15 ° C, still more preferably Tg-10 ° C, and still more preferably Tg-5 ° C. Further, the upper limit of the first temperature T ₁ is more preferably Tg + 15 ° C., further preferably Tg + 10 ° C., and still more preferably Tg + 5 ° C. For example, the first temperature T ₁ is a temperature in the range of Tg−20 ° C. ≦ T ₁ ≦ Tg + 10 ° C. By setting the first temperature T ₁ within the above temperature range, a high Li ion conductive phase with high crystallinity can be finally obtained, and a sulfide solid electrolyte material having high Li ion conductivity can be obtained. .

Heat treatment at the first temperature T ₁ of the first raised to temperatures T _1, in the first range of temperatures T _1, preferably 1 hour or more, more preferably 5 hours or more, more preferably 10 Holding for more than 20 hours, even more preferably more than 20 hours. The longer the holding time, the lower the first temperature T ₁ can be, and away from T _cx . When the temperature difference between T _cx and T _c1 is sufficiently large, the first temperature T ₁ may be increased to shorten the holding time.

The first temperature T ₁ is maintained within a temperature range in which the sulfide glass can be nucleated, more specifically, a temperature range near the glass transition point (Tg) of the sulfide glass, preferably the glass transition point Tg. As long as it is within the range of ± 20 ° C., and more preferably within the upper and lower limits of the first temperature T ₁ , they may be held at the same temperature or at different temperatures. For example, you may hold | maintain for a predetermined time at Tg-5 degreeC, or you may heat up over a predetermined time from the temperature of Tg-20 degreeC to the temperature of Tg + 10 degreeC. The upper limit of the holding time at the first temperature is not particularly limited, but can be, for example, within 100 hours or within 50 hours.

  The heat treatment at the nucleation temperature is preferably performed in an inert gas atmosphere such as an Ar gas atmosphere or a reduced pressure atmosphere (particularly in a vacuum). This is because deterioration (for example, oxidation) of the sulfide solid electrolyte can be prevented. The method for the heat treatment is not particularly limited, and examples thereof include a method using a firing furnace.

(Heat treatment process at crystal growth temperature)
The method according to the present invention includes heat-treating a sulfide glass at a nucleation temperature and then heat-treating at a crystal growth temperature. The heat treatment at the crystal growth temperature preferably includes a heat treatment at a second temperature T _{2 of} (T _c1 −20 ° C.) or more and (T _cx −40 ° C.) or less.

The lower limit of the second temperature T ₂ is more preferably T _c1 −15 ° C., further preferably T _c1 −10 ° C., and still more preferably T _c1 −5 ° C. Further, the upper limit of the second temperature T ₂ is more preferably T _cx −50 ° C., further preferably T _cx −60 ° C., and still more preferably T _cx −70 ° C. For example, the second temperature T ₂ is a temperature satisfying an expression in the range of T _c1 −10 ° C. ≦ T ₂ ≦ T _cx −50 ° C. By setting the second temperature T ₂ within the above temperature range, the crystallinity of the high Li ion conducting phase of the sulfide solid electrolyte can be further increased.

Heat treatment in the second temperature T _2, the second raised to temperature T _2, in a second range of temperature T _2, preferably 1 hour or more, more preferably 5 hours or more, more preferably 10 Holding for more than 20 hours, even more preferably more than 20 hours. The longer the holding time, the lower the second temperature T ₂ can be, and away from T _cx . When the temperature difference between T _cx and T _c1 is sufficiently large, the second temperature T ₂ may be increased to shorten the holding time.

The second temperature T ₂ can be maintained at the same temperature as long as it is within a temperature range in which crystal growth of a high ion conduction phase can be performed, preferably within the upper and lower limits of the first temperature T _2. May be kept at different temperatures. For example, the temperature may be maintained at T _c1 −5 ° C. for a predetermined time, or the temperature may be increased from a temperature of T _c1 −10 ° C. to a temperature of T _cx −50 ° C. over a predetermined time. The upper limit of the holding time at the second temperature is not particularly limited, but can be, for example, within 100 hours or within 50 hours.

  The heat treatment at the crystal growth temperature is preferably performed in an inert gas atmosphere such as an Ar gas atmosphere or a reduced pressure atmosphere (particularly in a vacuum). This is because deterioration (for example, oxidation) of the sulfide solid electrolyte can be prevented. The method for the heat treatment is not particularly limited, and examples thereof include a method using a firing furnace.

(Sulfide solid electrolyte material)
Sulfide solid electrolyte material obtained by the method according to the present invention is a _{LiI-LiX-Li 2 S-} P 2 S 5 sulfide solid electrolyte material (wherein, X is Cl, F or Br,), Glass ceramics. In this specification, glass ceramics refers to a material obtained by crystallizing sulfide glass. Whether it is glass ceramics can be confirmed by, for example, an X-ray diffraction method.

  The sulfide solid electrolyte material obtained by the method according to the present invention may or may not have a LiI peak in X-ray diffraction measurement, but the latter is preferred. This is because the Li ion conductivity is high. The same applies to LiX (wherein X is Cl, F, or Br).

  The sulfide solid electrolyte material obtained by the method according to the present invention has peaks at 2θ = 20.2 ° and 23.6 ° in X-ray diffraction measurement using CuKα rays, and 2θ = 21.0. The peaks at ° and 28.0 ° are low or have no peaks at 2θ = 21.0 ° and 28.0 °.

  The sulfide solid electrolyte material obtained by the method according to the present invention has a high Li ion conducting phase having peaks at 2θ = 20.2 ° and 23.6 ° in X-ray diffraction measurement using CuKα rays, and Because of its high crystallinity, it has high Li ion conductivity. Furthermore, the sulfide solid electrolyte material obtained by the method according to the present invention has low peaks at 2θ = 21.0 ° and 28.0 ° indicating the presence of a low Li ion conducting phase, or 2θ = 21.0 °. And it has high Li ion conductivity even in the absence of the 28.0 ° peak. It is particularly preferred that the peaks at 2θ = 20.2 ° and 23.6 ° have no peaks at 2θ = 21.0 ° and 28.0 °, in which case the sulfurization obtained by the method according to the invention The solid electrolyte material has a high Li ion conduction phase as a single phase, and can obtain high Li ion conductivity.

  In the sulfide solid electrolyte material obtained by the method according to the present invention, the half width of the peak at 2θ = 20.2 ° is preferably 0.64 ° or less, more preferably 0.57 ° or less, and further preferably 0. .47 ° or less. When the sulfide solid electrolyte has a peak at 2θ = 20.2 ° having such a half-width, it means that a high ion conductive phase having higher crystallinity exists and has a higher Li ion conductivity. It shows that a sulfide solid electrolyte is obtained. Here, the half width refers to the full width at half maximum (FWHM) of the peak at 2θ = 20.2 °.

  In the powder X-ray diffraction analysis, the peak position is read from the peak top. In the present specification, the peak at 2θ = 20.2 ° means not only a strict peak at 2θ = 20.2 ° but also a peak within a range of 2θ = 20.2 ° ± 0.5 °. Depending on the crystal state, the position of the peak may slightly move back and forth, so it is defined as above. Similarly, the peak at 2θ = 23.6 ° is not only a strict peak at 2θ = 23.6 °, but also a peak within a range of 2θ = 23.6 ° ± 0.5 °. In addition to the 2θ = 20.2 ° and 23.6 °, the high Li ion conduction phase usually has peaks at 2θ = 29.4 °, 37.8 °, 41.1 °, 47.0 °. Have. These peak positions may also move back and forth within a range of ± 0.5 °.

  Similarly, the peak at 2θ = 21.0 ° is not only a strict peak at 2θ = 21.0 ° but also a peak within a range of 2θ = 21.0 ° ± 0.5 °. Depending on the crystal state, the position of the peak may slightly move back and forth, so it is defined as above. Similarly, the peak at 2θ = 28.0 ° is not only a strict peak at 2θ = 28.0 ° but also a peak within a range of 2θ = 28.0 ° ± 0.5 °. In addition to 2θ = 21.0 ° and 28.0 °, the low Li ion conducting phase is usually 2θ = 32.0 °, 33.4 °, 38.7 °, 42.8 °, 44. It has a peak at 2 °. These peak positions may also move back and forth within a range of ± 0.5 °.

  In the sulfide solid electrolyte material obtained by the method according to the present invention, the peak intensity I20.2 / I21.0 of 2θ = 20.2 ° with respect to the peak intensity of 2θ = 21.0 ° is preferably 2.5 or more. More preferably, it is 2.7 or more, more preferably 5 or more, still more preferably 10 or more, and particularly preferably, no peaks are observed at 2θ = 21.0 ° and 28.0 °.

  In the sulfide solid electrolyte material obtained by the method according to the present invention, I21.0 / I20.2 is preferably 0.4 or less, more preferably 0.37 or less, and further preferably 0.2 or less. And even more preferably 0.1 or less. I21.0 / I20.2 has a reciprocal relationship with I20.2 / I21.0.

The sulfide solid electrolyte material obtained by the method according to the present invention has high Li ion conductivity, and Li ion conductivity at room temperature is preferably 1 × 10 ⁻⁴ S / cm or more, more preferably 1 × 10 ^{−. 3} S / cm or more.

  The sulfide solid electrolyte material obtained by the method according to the present invention can be used for any application that requires Li ion conductivity. Among these, the sulfide solid electrolyte material is preferably used for a battery, and more preferably used for an all-solid battery.

  An all-solid battery can be produced using the sulfide solid electrolyte material obtained by the method according to the present invention. The all solid state battery includes a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer, And at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer can contain the sulfide solid electrolyte material described above.

  By using the sulfide solid electrolyte material obtained by the method according to the present invention, an all-solid battery having high Li ion conductivity can be obtained. As a result, the output of the battery can be increased.

  FIG. 5 is a schematic cross-sectional view showing an example of an all-solid battery. An all solid state battery 100 shown in FIG. 5 includes a positive electrode active material layer 1 containing a positive electrode active material, a negative electrode active material layer 2 containing a negative electrode active material, and between the positive electrode active material layer 1 and the negative electrode active material layer 2. The solid electrolyte layer 3 formed on the cathode, the positive electrode current collector 4 for collecting current of the positive electrode active material layer 1, the negative electrode current collector 5 for collecting current of the negative electrode active material layer 2, and these members are housed. A battery case 6 is provided. At least one of the positive electrode active material layer 1, the negative electrode active material layer 2, and the solid electrolyte layer 3 can contain a sulfide solid electrolyte material obtained by the method according to the present invention.

  The positive electrode active material layer 1 is a layer containing at least a positive electrode active material, and may further contain at least one of a solid electrolyte material, a conductive material, and a binder as necessary. As the solid electrolyte material, a sulfide solid electrolyte material obtained by the method according to the present invention can be used.

  The content of the sulfide solid electrolyte material in the positive electrode active material layer 1 is preferably in the range of 0.1% by volume to 80% by volume, more preferably in the range of 1% by volume to 60% by volume, and further preferably 10% by volume. % To 50% by volume.

The positive electrode active material is not particularly limited. For example, a rock salt layered active material such as LiCoO 2, LiMnO ₂ , LiNiO ₂ , LiVO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , Examples include spinel active materials such as LiMn ₂ O ₄ and Li (Ni _0.5 Mn _1.5 ) O ₄ , and olivine active materials such as LiFePO ₄ , LiMnPO ₄ , LiNiPO ₄ , and LiCuPO ₄ . Si-containing oxides such as Li ₂ FeSiO ₄ and Li ₂ MnSiO ₄ may be used as the positive electrode active material.

  Examples of the shape of the positive electrode active material include a particle shape, and among them, a spherical shape or an elliptical shape is preferable. Moreover, when a positive electrode active material is a particle shape, it is preferable that the average particle diameter exists in the range of 0.1 micrometer-50 micrometers, for example. Further, the content of the positive electrode active material in the positive electrode active material layer is, for example, preferably in the range of 10% by volume to 99% by volume, and more preferably in the range of 20% by volume to 99% by volume.

  Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. Examples of the binder include fluorine-containing binders such as PTFE and PVDF. The thickness of the positive electrode active material layer is preferably in the range of 0.1 μm to 1000 μm, for example.

  The negative electrode active material layer 2 is a layer containing at least a negative electrode active material, and may further contain at least one of a solid electrolyte material, a conductive material, and a binder as necessary. As the solid electrolyte material, a sulfide solid electrolyte material obtained by the method according to the present invention can be used.

  The content of the sulfide solid electrolyte material in the negative electrode active material layer 2 is preferably in the range of 0.1% by volume to 80% by volume, more preferably in the range of 1% by volume to 60% by volume, and particularly preferably. It is in the range of 10% to 50% by volume.

  Examples of the negative electrode active material include a metal active material and a carbon active material. Examples of the metal active material include In, Al, Si, and Sn. On the other hand, examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon.

  The content of the negative electrode active material in the negative electrode active material layer is, for example, preferably in the range of 10% by volume to 99% by volume, and more preferably in the range of 20% by volume to 99% by volume. Note that the conductive material and the binder are the same as those used for the positive electrode active material layer described above. The thickness of the negative electrode active material layer is preferably in the range of 0.1 μm to 1000 μm, for example.

  The solid electrolyte layer 3 is a layer formed between the positive electrode active material layer 1 and the negative electrode active material layer 2 and is a layer composed of a solid electrolyte material. As the solid electrolyte material contained in the solid electrolyte layer, a sulfide solid electrolyte material obtained by the method according to the present invention can be used.

  The content of the sulfide solid electrolyte material in the solid electrolyte layer 3 is not particularly limited as long as a desired insulating property can be obtained, but is preferably 10% by volume or more, more preferably 50% by volume or more. More preferably, the solid electrolyte layer is composed only of the sulfide solid electrolyte material obtained by the method according to the present invention.

  The solid electrolyte layer 3 may contain a binder. This is because a solid electrolyte layer having flexibility can be obtained by containing a binder. The binder is the same as that used for the positive electrode active material layer described above. The thickness of the solid electrolyte layer is, for example, preferably in the range of 0.1 μm to 1000 μm, and more preferably in the range of 0.1 μm to 300 μm.

  Examples of the material of the positive electrode current collector 4 include SUS, aluminum, nickel, iron, titanium, and carbon. Examples of the material of the negative electrode current collector 5 include SUS, copper, nickel, and carbon. The thickness, shape, and the like of the positive electrode current collector 4 and the negative electrode current collector 5 can be appropriately selected according to the application of the all-solid battery. As the battery case 6 used in the present invention, a general battery case of an all solid state battery can be used. Examples of the battery case 6 include a SUS battery case.

  The all solid state battery may be a primary battery or a secondary battery, but is preferably a secondary battery. This is because it can be repeatedly charged and discharged and is useful, for example, as a vehicle-mounted battery. Examples of the shape of the all solid state battery include a coin type, a laminate type, a cylindrical type, and a square type.

  The manufacturing method of an all-solid battery is not particularly limited, and a method similar to a general manufacturing method of an all-solid battery can be used. As an example of a method for producing an all-solid-state battery, a power generation element is manufactured by sequentially pressing a material constituting the positive electrode active material layer, a material constituting the solid electrolyte layer, and a material constituting the negative electrode active material layer, A method of storing the power generation element in the battery case and caulking the battery case can be exemplified.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

  Hereinafter, the present invention will be described in more detail with reference to examples. Unless otherwise specified, each operation such as weighing, synthesis, and drying was performed in an Ar atmosphere.

(Comparative Example 1)
Starting from Li ₂ S (manufactured by Nippon Kagaku Kogyo), P ₂ S ₅ (manufactured by Aldrich), LiI (manufactured by Nichiho Chemical), and LiBr (manufactured by high-purity chemical), 0.586 g of Li ₂ S, P ₂ 0.95 g of S ₅ , 0.284 g of LiI, and 0.185 g of LiBr were weighed and mixed for 5 minutes in an agate mortar. The mixture is put in 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 ZrO ₂ balls (φ = 5 mm, 53 g) are further charged. Completely sealed. This container was attached to a planetary ball mill (P7 made by Fritsch), and mechanical milling was performed for 20 hours at a base plate rotation speed of 500 rpm. Then, the heptane was removed by drying at 110 degreeC for 1 hour, and sulfide glass was obtained. The composition of the obtained sulfide glass is 10LiI · 10LiBr · 80 (0.75Li ₂ S · 0.25P ₂ S ₅ ) (mol%) in terms of mole, and this composition is designated as composition A.

  Next, 0.5 g of the obtained sulfide glass was vacuum-sealed in a quartz tube, and heat treatment was performed at 185 ° C. The temperature was raised from room temperature to 185 ° C. at 1 ° C./min. After reaching 185 ° C. and held for 10 hours, it was naturally cooled to obtain a sulfide solid electrolyte as glass ceramic.

Example 1
0.5 g of the sulfide glass obtained in the same manner as in Comparative Example 1 was vacuum-sealed in a quartz tube, and the temperature was raised from room temperature at 1 ° C./min according to the heat treatment profile shown in FIG. Hold at a temperature of 150 ° C. for 5 hours, then raise the temperature at 1 ° C./min, hold at a second temperature of 185 ° C. for 5 hours, and then naturally cool to provide a sulfide solid electrolyte that is a glass ceramic Got.

(Example 2)
A sulfide solid electrolyte, which is a glass ceramic, was obtained in the same manner as in Example 1 except that the first temperature was 170 ° C.

(Example 3)
A sulfide solid electrolyte, which is a glass ceramic, was obtained in the same manner as in Example 1 except that the first temperature was 175 ° C.

(Comparative Example 2)
Starting from Li ₂ S (manufactured by Nippon Kagaku Kogyo), P ₂ S ₅ (manufactured by Aldrich), and LiI (manufactured by Niho Chemical), 0.52 g of Li ₂ S, 0.900 g of P ₂ S ₅ , and A sulfide glass was obtained in the same manner as in Example 1 except that 0.542 g of LiI was weighed and used. The composition of the obtained sulfide glass is 20LiI · 80 (0.75Li ₂ S · 0.25P ₂ S ₅ ) (mol%) in terms of mole, and this composition is designated as composition B. Next, a sulfide solid electrolyte was obtained in the same manner as in Example 1.

  Table 1 shows the temperature conditions of the heat treatment in Examples 1 to 3 and Comparative Examples 1 and 2.

(DTA measurement)
DTA analysis was performed on the sulfide glasses of compositions A and B, and T _c1 , T _cx , T _c2 , and T _g were measured. T _c1 , T _cx , and T _c2 were the peak top temperatures, and T _g was the temperature at the intersection of the low temperature side background of T _c1 and the tangent at the inflection point of the endothermic peak. For the measurement, a TG-DTA apparatus (Thermo plus EVO, manufactured by Rigaku) was used. An aluminum sample pan was used, and α-Al ₂ O ₃ powder was used as a reference sample. Using 23 mg of the measurement sample, the temperature was raised from room temperature to 400 ° C. at 10 ° C./min in an Ar gas atmosphere, and DTA analysis was performed. FIG. 2 shows the DTA analysis result of the sulfide glass, and Table 2 shows the measurement results of T _c1 , T _cx , T _c2 , and T _g .

As shown in Table 2 and FIG. 2, T _g of the sulfide glass of composition A is around 165 ° C., T _c1 is around 190 ° C., T _c2 is around 273 ° C., and T _cx is T _c2 . Overlapping and not seen. In composition B, T _g was not observed, and T _cx was observed at around 244 ° C.

(Powder X-ray diffraction measurement)
Powder X-ray diffraction analysis was performed on the sulfide glasses having compositions A and B using a powder X-ray diffraction (XRD) apparatus (RINT-UltimaIII) manufactured by Rigaku. A sample was placed in a dome-shaped jig and measured in the range of 2θ = 10 ° to 60 ° in an inert atmosphere of Ar gas. The scan speed was 5 ° / min and the sampling width was 0.02 °. FIG. 6 shows a measured X-ray diffraction profile in the range of 2θ = 10 ° to 45 °. In the X-ray diffraction profiles of the sulfide glasses having the compositions A and B, no clear crystal peak was observed, and it was confirmed that the whole was amorphous.

  The sulfide solid electrolyte materials obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were subjected to powder X-ray diffraction analysis under the same conditions as described above. FIG. 4 shows a measured X-ray diffraction profile in the range of 2θ = 10 ° to 45 °. The half width of the peak at 2θ = 20.2 ° was determined from the measured X-ray diffraction profile. Table 3 shows the full width at half maximum of the peak at 2θ = 20.2 °.

  As shown in Table 3 and FIG. 4, in the sulfide solid electrolytes obtained in Examples 1 to 3 subjected to the two-stage heat treatment, the half width of the peak at 2θ = 20.2 ° is 0.64 or less. It was found that the crystallinity was high.

(Li ion conductivity measurement)
About the sulfide solid electrolyte material obtained by Examples 1-3 and Comparative Examples 1-2, Li ion conductivity was measured. First, the sample was cold-pressed at a pressure of 4 ton / cm ² to produce a pellet of φ11.29 mm and a thickness of about 500 μm. Next, the pellets were placed in an inert atmosphere container filled with Ar gas, and measurement was performed. For the measurement, Solartron (SI1260) manufactured by Toyo Corporation was used. Moreover, the measurement temperature was adjusted to 25 ° C. in a thermostatic bath. The results are shown in Table 4 and FIG.

  As shown in Table 4 and FIG. 3, the sulfide solid electrolytes obtained in Examples 1 to 3 that were subjected to the two-stage heat treatment exhibited high Li ion conductivity.

DESCRIPTION OF SYMBOLS 100 All-solid-state battery 1 Positive electrode active material layer 2 Negative electrode active material layer 3 Solid electrolyte layer 4 Positive electrode collector 5 Negative electrode collector 6 Battery case

Claims (4)

_{LiI-LiX-Li 2 S-} P 2 S 5 sulfide solid electrolyte (wherein, X is Cl, F or Br,) a process for the preparation of,
Amorphizing a raw material composition containing LiI, LiX (wherein X is Cl, F, or Br), Li ₂ S, and P ₂ S ₅ to obtain a sulfide glass;
Heating to the nucleation temperature of the sulfide glass and holding at the nucleation temperature to heat-treat the sulfide glass; and heat-treating the heat-treated sulfide glass at the crystal growth temperature of the sulfide glass To do,
Only including,
Heat-treating at the nucleation temperature includes holding at a temperature T ₁ within a range of the glass transition point Tg ± 20 ° C. of the sulfide glass ;
Production method.   The manufacturing method according to claim 1, wherein X is Br. The manufacturing method according to claim 1 , wherein the temperature T ₁ satisfies an expression of Tg−20 ° C. ≦ T ₁ ≦ Tg + 10 ° C. In an X-ray diffraction measurement using CuKα rays, a high Li ion conducting phase having peaks at 2θ = 20.2 ° and 23.6 ° is c1, and peaks at 2θ = 21.0 ° and 28.0 °. In the differential thermal analysis, when the low Li ion conduction phase is cx, the temperature of the exothermic peak of _c1 is T _c1, and the temperature of the exothermic peak of _cx is T _cx ,
Subjected to heat treatment in the crystal growth temperature, including (T _c1 -20 ℃) or higher and (T _cx -40 ℃) be maintained at a temperature T ₂ within the range, any one of the claims 1-3 The production method according to item.

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