JP2012121789A - Ionic conductive glass ceramics, manufacturing method therefor and all-solid-state secondary battery containing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ionic conductive glass ceramics at low cost against the backdrop of abundant sodium resources.SOLUTION: The ionic conductive glass ceramics is represented by general formula (I): NaS-MS(M is selected from P, Si, Ge, B and Al, x and y are integers providing stoichiometric ratio corresponding to the kinds of M, and NaS is contained at more than 67 mol% and less than 80 mol%).

Description

  The present invention relates to an ion conductive glass ceramic, a method for producing the same, and an all solid state secondary battery including the same. More specifically, the present invention relates to an ion conductive glass ceramic that can be provided at a low cost against a background of abundant sodium resources, a method for producing the same, and an all solid state secondary battery including the same.

Lithium secondary batteries have high voltage and high capacity, and are therefore widely used as power sources for mobile phones, digital cameras, video cameras, notebook computers, electric vehicles and the like. Generally, lithium secondary batteries in circulation use a liquid electrolyte in which an electrolytic salt is dissolved in a non-aqueous solvent as an electrolyte. Since non-aqueous solvents contain a lot of flammable solvents, it is desired to ensure safety.
In order to ensure safety, an all-solid secondary battery using a so-called solid electrolyte in which an electrolyte is formed from a solid material Li ₂ S—P ₂ S ₅ without using a non-aqueous solvent has been proposed. (Non-Patent Document 1).

M. Tatsumisago et.al., Funct. Mater. Lett., 1 (2008) 31

  In recent years, demand for lithium secondary batteries has been increasing in order to store electric power in automobiles such as electric vehicles and hybrid vehicles, power generation devices such as solar cells and wind power generation. However, since the lithium secondary battery uses lithium that has a small reserve and is unevenly distributed, there are concerns that supply cannot catch up with demand, and there is a problem of high cost.

The inventors of the present invention believe that the above concerns and problems also occur in all-solid secondary batteries. Therefore, a battery using sodium, which has abundant resources, can be cited as a post lithium secondary battery. A sodium ion conductive solid is used for a battery using sodium, and β-alumina is widely known as the sodium ion conductive solid. This material exhibits a sodium ion conductivity of 10 ⁻³ S cm ⁻¹ or more at room temperature [Reference: X. Lu et al., Journal of Power Sources, 195 (2010) 2431-2442.]. However, the synthesis of this material requires high-temperature firing at 1600 ° C. or higher, and there is a problem that solid interface bonding with the electrode active material is difficult. A material exhibiting high electrical conductivity as a powder molded body obtained only by pressing without requiring firing at a high temperature is important for constructing an electrode-electrolyte interface of a room temperature operation type all solid state battery. The inventors investigated existing literatures, but have not found literatures on solid materials having sufficient sodium ion conductivity as a powder compact at room temperature.

Therefore, the inventors tried to use Na ₂ S instead of Li ₂ S, but thought that there was room for further improvement from the viewpoint of ion conductivity. Therefore, as a result of further intensive studies, the inventors obtained a glass by subjecting a raw material of a solid material containing Na ₂ S to a mechanical milling process, and then heat-treating the glass at a temperature equal to or higher than its glass transition point. It was found that the ion conductivity is greatly improved with the converted glass ceramics, and the present invention has been achieved.

Thus, according to the present invention, the general formula (I): Na ₂ S—M _x S _y (M is selected from P, Si, Ge, B, Al, and x and y are chemicals depending on the type of M, An ion-conducting glass-ceramic represented by an integer giving a stoichiometric ratio and containing Na ₂ S of greater than 67 mol% and less than 80 mol% is provided.

Furthermore, according to the present invention, there is provided a method for producing the ion conductive glass ceramic,
Formula (I): a step of obtaining a glass denoted by the raw material mixture containing Na ₂ S-M _x S give _y Na ₂ S and M _x S _y in predetermined proportions to the mechanical milling process, the glass There is provided a method for producing an ion conductive glass ceramic characterized by including a step of converting to an ion conductive glass ceramic by heat treatment at a temperature equal to or higher than the glass transition point.

  In addition, according to the present invention, there is provided at least a positive electrode, a negative electrode, and a solid electrolyte layer positioned between the positive electrode and the negative electrode, and the solid electrolyte layer includes the ion conductive glass ceramics. A solid secondary battery is provided.

ADVANTAGE OF THE INVENTION According to this invention, the glass ceramics which have high ion conductivity independent of the amount of resources of lithium can be provided.
_{Further, Na 2 S-M x S} y is the case of _{Na 2 S-P 2 S 5} , can provide a glass ceramic having a higher ionic conductivity.
According to the method for producing glass ceramics of the present invention, it is possible to provide glass ceramics having high ion conductivity that does not depend on the amount of lithium resources by a simple method of mechanical milling and heat treatment.

When the mechanical milling process is performed using a planetary ball mill under conditions of 50 to 600 revolutions / minute, 0.1 to 50 hours, and 1 to 100 kWh / kg of raw material mixture, glass ceramics having higher ion conductivity Can provide.
Since the all-solid-state secondary battery of the present invention uses a solid electrolyte layer containing sodium, it can be provided at a low cost against the background of abundant sodium resources.

2 is an XRD pattern of the glass of Example 1. FIG. 2 is a DTA curve of the glass of Example 1. It is a Raman spectrum of the glass of Example 1. It is a principal part enlarged view of FIG. 3 is a ³¹ PMAS-NMR spectrum of the glass of Example 1. It is a graph which shows the temperature dependence of the electrical conductivity of the glass of Example 1, and glass ceramics. It is a graph which shows the electrical conductivity in room temperature of glass and glass ceramics of Example 1, and the activation energy of conduction. 2 is an XRD pattern of the glass ceramic of Example 1. FIG. 3 is a ³¹ PMAS-NMR spectrum of the glass ceramic of Example 1. It is a graph which shows the relationship of the absolute value | Z | of the impedance with respect to the frequency of the glass of Example 3, and glass ceramics. It is a graph which shows the relationship of the electrical conductivity with respect to the temperature of various sintered compacts shown in Example 4, glass, and glass ceramics.

(Ion conductive glass ceramics)
The glass ceramics may be in a state in which a crystalline part is dispersed in an amorphous glass component. The ratio of the crystalline part is preferably 50% by weight or more, and more preferably 80% by weight or more with respect to the entire glass ceramic. The proportion of the crystalline part can be measured by solid state NMR.
Furthermore, the glass ceramics preferably have no glass transition point present in the corresponding glass.

The ion conductive glass ceramic of the present invention is represented by the general formula (I): Na ₂ S—M _x S _y (M is selected from P, Si, Ge, B, Al, and x and y depend on the type of M. And an integer giving a stoichiometric ratio, and Na ₂ S is contained in an amount greater than 67 mol% and less than 80 mol%. Specific examples include Na ₂ S—P ₂ S ₅ , Na ₂ S—SiS ₂ , Na ₂ S—GeS ₂ , Na ₂ S—B ₂ S ₃ , and Na ₂ S—Al ₂ S ₃ . Of these, Na ₂ S—P ₂ S ₅ is particularly preferred. Furthermore, other ion conductive materials such as NaI and Na ₃ PO ₄ may be added.
Furthermore, Na ₂ S-M _x S _y contains greater than 67 mol% and less than 80 mol% Na ₂ S. If it is this range, ion conductivity can be improved rather than corresponding glass. Moreover, greater than 70 mole%, more preferably containing Na ₂ S of less than 80 mol%, more preferably containing 73 to 77 mol% of Na ₂ S.

(Production method of ion conductive glass ceramics)
The manufacturing method of ion conductive glass ceramics is:
(I) the general formula _{(I): Na 2 S-} M x S and Na ₂ S and M _x S _y giving _y obtain a glass denoted by the raw material mixture to the mechanical milling process including at a predetermined ratio step,
(Ii) converting the glass into ion conductive glass ceramics by heat-treating the glass at a temperature equal to or higher than its glass transition point.

(1) Step (i)
The mechanical milling process in the step (i) is not particularly limited to the processing apparatus and the processing conditions as long as the raw materials can be sufficiently mixed and reacted.
As a processing apparatus, a ball mill can be used normally. A ball mill is preferable because large mechanical energy can be obtained. Among the ball mills, the planetary ball mill is preferable because the pot rotates and the base plate revolves and high impact energy can be generated efficiently.

  The processing conditions can be appropriately set according to the processing apparatus to be used. For example, when a ball mill is used, the raw materials can be mixed and reacted more uniformly as the rotational speed is higher and / or the treatment time is longer. Note that “and / or” means A, B, or A and B when expressed as A and / or B. Specifically, when a planetary ball mill is used, conditions of a rotation speed of 50 to 600 revolutions / minute, a treatment time of 0.1 to 50 hours, and 1 kg of raw material mixture of 1 to 100 kWh are exemplified. More preferable processing conditions include a rotation speed of 200 to 500 rotations / minute, a processing time of 1 to 20 hours, and 1 to 6 kg of a raw material mixture.

(2) Step (ii)
The glass obtained in the above step (i) is subjected to a heat treatment to be converted into ion conductive glass ceramics. This heat treatment is performed at a temperature equal to or higher than the glass transition point of the glass.
The glass transition point (T _g ) varies depending on the ratio of Na ₂ S and M _x S _y , but is, for example, in the range of 180 to 200 ° C. in the case of Na ₂ S—P ₂ S ₅ . The first crystallization temperature (T _c ) is in the range of 190 to 240 ° C. Although the upper limit of heat processing temperature is not specifically limited, Usually, it is 1st crystallization temperature +100 degreeC.
The heat treatment time is a time during which glass can be converted into ion conductive glass ceramics, and is short when the heat treatment temperature is high and long when the heat treatment temperature is low. The heat treatment time is usually in the range of 0.1 to 10 hours.

(Use of ion conductive glass ceramics)
Ion conductive glass ceramics can be used for any application as long as ion conductivity is required. For example, the solid electrolyte layer of an all-solid-state secondary battery and an all-solid capacitor, the conductive layer of a sensor, etc. are mentioned. Among these, it is preferable to use for the solid electrolyte layer of an all-solid-state secondary battery.
The all solid state secondary battery is not particularly limited, but usually includes at least a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive electrode and the negative electrode.

(1) Solid electrolyte layer The solid electrolyte layer contains the ion conductive glass ceramics (Na ₂ S-M _x S _y ). In addition to the ion conductive glass ceramic, an electrolyte (for example, NaI, Na ₃ PO ₄ or the like) that is usually used in an all-solid secondary battery may be included. The proportion of the ion conductive glass ceramics in the solid electrolyte layer is preferably 90% by weight or more, and more preferably the total amount. The thickness of the solid electrolyte layer is preferably 1 to 1000 μm, and more preferably 1 to 200 μm. The solid electrolyte layer can be obtained as a pellet by pressing the raw material, for example.

(2) Positive electrode A positive electrode is not specifically limited. The negative electrode may be composed of only the negative electrode active material, and may be mixed with a binder, a conductive agent, an electrolyte, and the like.
As the positive electrode active material, various transition metal compounds such as Na _0.44 MnO ₂ , NaNi _0.5 Mn _0.5 O ₂ , FeS, TiS ₂ , NaCoO ₂ , NaFeO ₂ , Na ₃ V ₂ (PO ₄ ) ₃ , NaMn ₂ O ₄ Etc.
Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyvinyl acetate, polymethyl methacrylate, and polyethylene.
Examples of the conductive agent include natural graphite, artificial graphite, acetylene black, ketjen black, Denka black, carbon black, vapor grown carbon fiber (VGCF) and the like.
Examples of the electrolyte include an electrolyte used for a solid electrolyte layer.
The positive electrode can be obtained as a pellet by, for example, mixing a positive electrode active material and optionally a binder, a conductive agent, an electrolyte, and the like, and pressing the obtained mixture.
The positive electrode may be formed on a current collector such as aluminum or copper.

(3) Negative electrode A negative electrode is not specifically limited. The negative electrode may be composed of only the negative electrode active material, and may be mixed with a binder, a conductive agent, an electrolyte, and the like.
As the negative electrode active material, various transitions such as metals such as Na, In, Sn, Na alloys, graphite, hard carbon, Li _4/3 Ti _5/3 O ₄ , Na ₃ V ₂ (PO ₄ ) ₃ , SnO, etc. A metal oxide etc. are mentioned.
As the binder, the conductive agent, and the electrolyte, any of those mentioned in the column of the positive electrode can be used.
The negative electrode can be obtained in the form of pellets by, for example, mixing a negative electrode active material and optionally a binder, a conductive agent, an electrolyte, and the like, and pressing the obtained mixture. Moreover, when using the metal sheet (foil) which consists of a metal or its alloy as a negative electrode active material, can be used as it is.
The negative electrode may be formed on a current collector such as aluminum or copper.

(4) Manufacturing method of all-solid-state secondary battery An all-solid-state secondary battery can be obtained by, for example, laminating and pressing a positive electrode, an electrolyte layer, and a negative electrode.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.
Example 1
Step (i): Mechanical milling treatment Na ₂ S (purity 99%, manufactured by Aldrich) and P ₂ S ₅ (purity 99%, manufactured by Aldrich) were added at 67:33, 70:30, 75:25 and 80:20 moles. Each was put into a planetary ball mill. After the addition, 67Na ₂ S-33P ₂ S ₅ , 70Na ₂ S-30P ₂ S ₅ , 75Na ₂ S-25P ₂ S ₅ and 80Na ₂ S-20P ₂ S ₅ were obtained by mechanical milling.
As the planetary ball mill, Pulverisette P-7 manufactured by Fritsch was used, and the pot and balls were made of ZrO ₂ , and a mill containing 500 balls of 4 mm in diameter in a 45 ml pot was used. The mechanical milling process was performed for 20 hours in a dry nitrogen glove box at a rotation speed of 510 rpm, room temperature.

The above production method is described in Akito Hayashi et al. , Journal of Non-Crystalline Solids 356 (2010) 2670-2673.
The above four kinds of Na ₂ S—P ₂ S ₅ 80 mg were pressed (pressure 370 MPa / cm ² ) to obtain pellets having a diameter of 10 mm and a thickness of about 1 mm.

FIG. 1 shows an XRD pattern of the obtained glass powder, FIG. 2 shows a DTA curve, FIG. 3 shows a Raman spectrum, FIG. 4 shows an enlarged view of a main part of FIG. 3, and FIG. 5 shows ³¹ PMAS-NMR.
From FIG. 1, it is shown that 67Na ₂ S-33P ₂ S ₅ , 70Na ₂ S-30P ₂ S ₅ and 75Na ₂ S-25P ₂ S ₅ obtained an amorphous material, and 80Na ₂ S-20P. ₂ S ₅ indicates that some Na ₂ S remains in addition to amorphous.
From FIG. 2, glass transition points were confirmed in all of 67Na ₂ S-33P ₂ S ₅ , 70Na ₂ S-30P ₂ S ₅ , 75Na ₂ S-25P ₂ S ₅ and 80Na ₂ S-20P ₂ S ₅ , It can be seen that these amorphous materials are in a glass state. In addition, a glass transition point is between 180-200 degreeC.

3 and 4, 67Na ₂ S-33P ₂ S ₅ mainly shows a peak derived from P ₂ S ₇ ^4- . In 70Na ₂ S-30P ₂ S ₅ , as the proportion of Na ₂ S increases, the peak derived from P ₂ S ₇ ^4- decreases, and the peak derived from PS ₄ ^3- increases instead of the peak. 75Na ₂ S-25P ₂ S ₅ and 80Na ₂ S-20P ₂ S ₅ , it is shown that a peak derived from PS ₄ ³⁻ is mainly observed. 3 and 4 are attributed to PS ₄ ³⁻ , P ₂ S ₇ ^4−, and P ₂ S ₆ ⁴⁻ , respectively, that Na ₂ S—P ₂ S ₅ Since the data in the system of ( ₂₎ could not be obtained, it is inferred from the data in the system of Li ₂ S—P ₂ S ₅ . Specifically, PS ₄ ^3- is 419cm ^-1, P ₂ S ₇ ^4- is 406cm ^-1, is set to P ₂ S ₆ ^4- is 382cm ^-1.
In FIG. 5, the same tendency as in FIGS. 3 and 4 is observed.

Step (ii): Heat treatment The pellets composed of the above four types of glass were heated from room temperature (25 ° C.) toward 280 ° C., which is equal to or higher than the crystallization temperature, to convert the glass into glass ceramics. Further, after reaching 280 ° C., the glass ceramic pellets were cooled toward room temperature. During this heating and cooling cycle, the conductivity of the pellet was measured about every 15 ° C. The measurement results are shown in FIGS. In the figure, black circles indicate glass ceramics, and white circles indicate glass.

FIG. 6A shows that 67Na ₂ S-33P ₂ S ₅ has almost no difference in electrical conductivity between the glass state and the glass ceramic state. 6 (b) to (d), 70Na ₂ S-30P ₂ S ₅ , 75Na ₂ S-25P ₂ S ₅ and 80Na ₂ S-20P ₂ S ₅ show the conductivity in the glass state and the glass ceramic state. It is shown that there is a difference. In particular, in the former two cases, the glass ceramic state shows higher conductivity than the glass state.
The results of measuring the activation energy (Ea) of the conduction between the glass and glass ceramic pellets are shown in Table 1 together with the conductivity values at room temperature. In Table 1, G means glass and GC means glass ceramics. Moreover, the result of Table 1 is put together in FIG. In FIG. 7, black circles and black triangles indicate glass ceramics, and white circles and white triangles indicate glass.

From FIG. 7 and Table 1, it can be seen that there is a difference in the conductivity and the activation energy of conduction between the glass state and the glass ceramic state.
The XRD pattern of _{67Na 2 S-33P 2 S 5} , 70Na 2 S-30P 2 S 5, 75Na 2 S-25P 2 S 5 and 80Na ₂ S-20P ₂ S ₅ after the heat treatment in FIG. 8, ³¹ PMAS-NMR Are shown in FIG. FIG. 8 also shows an XRD pattern of a Na ₃ PS ₄ crystal (tetragonal crystal) published in Document A below.
Reference A: M. Jansen et al. , Journal of Solid State Chemistry, 92 (1992) 110.

From FIG. 8, it can be seen that four types of Na ₂ S—P ₂ S ₅ are in a glass-ceramic state because there are peaks derived from the crystal structure as compared with FIG. Further, from FIG. 8, the _{80Na 2 S-20P 2 S 5} , is a similar peak pattern and Na ₃ PS ₄ crystal, according mol% of Na ₂ S is decreased, the different patterns and Na ₃ PS ₄ crystal Since the presence is observed, precipitation of a crystal different from the Na ₃ PS ₄ crystal is considered. In particular _{75Na 2 S-25P 2 S 5} , shows a pattern in 2θ position similar to the pattern of tetragonal Na ₃ PS _4, there exists a cubic Na ₃ PS ₄ resulted in no splitting of peaks it is conceivable that. In addition, in 67Na ₂ S-33P ₂ S ₅ , the crystal cannot be identified, and the precipitation of an unknown crystal is considered. It can also be seen that 70Na ₂ S-30P ₂ S ₅ is a pattern obtained by adding the patterns of 67Na ₂ S-33P ₂ S ₅ and 75Na ₂ S-25P ₂ S ₅ .

From FIG. 9, in 75Na ₂ S-25P ₂ S ₅ and 80Na ₂ S-20P ₂ S ₅ , a peak mainly derived from PS ₄ ^3- is seen, and in 67Na ₂ S-33P ₂ S ₅ , P ₂ S ₇ ^The peak derived from ^4- is mainly seen. In 70Na ₂ S-30P ₂ S ₅ , both peaks derived from PS ₄ ^3- and P ₂ S ₇ ^4- are observed.

Example 2
Na _0.44 MnO ₂ as the positive electrode active material, the glass ceramic made of 75Na ₂ S-25P ₂ S _{5 of} Example 2 as the electrolyte, and acetylene black as the conductive agent in a weight ratio of 40: 60: 6 (total weight 15.5 mg ), And then mixed and pressed to obtain a positive electrode.
A solid electrolyte layer was obtained by pressing 70 mg of 75Na ₂ S-25P ₂ S ₅ glass ceramic of Example 2.
Stainless steel was used for the negative electrode portion. More specifically, a negative electrode was obtained by precipitating metallic sodium on stainless steel during initial charging.
A positive electrode, a solid electrolyte layer, and a negative electrode were laminated and pressed to obtain an all-solid secondary battery. The obtained all solid state secondary battery had sufficient charge / discharge characteristics.

Example 3
In 75Na ₂ S-25P ₂ to produce pellets of a glass ceramics S _5, except that the temperature of the heat treatment of the corresponding glass from 280 ° C. to 270 ° C., in the same manner as in Example 1, 75Na ₂ S-25P ₂ to obtain a pellet of glass ceramics of S _5.
Further, 80 mg of β-alumina, which is a typical sodium ion conductive solid electrolyte, was pressed (pressure 370 MPa / cm ² ) to obtain pellets having a diameter of 10 mm and a thickness of about 1 mm. This pellet is not subjected to high-temperature sintering at 1800 ° C. or higher which is applied to a conventional β-alumina pellet for use as an electrolyte.

The resulting 75Na ₂ S-25P ₂ absolute value of the impedance for the frequency of the S glass ceramics ₅ pellets at room temperature (about 25 ℃) | Z | were measured. The measurement results are shown in FIG. FIG. 10 also shows the absolute value | Z | of room temperature impedance of 75Na ₂ S-25P ₂ S ₅ glass pellets before conversion into glass ceramics. Further, FIG. 10 also shows the absolute value | Z | of impedance when the β-alumina pellets are heated at 70 ° C. and 120 ° C. Attempts were made to measure the absolute value | Z | of the β-alumina pellet at room temperature, but the impedance was too large to be measured, and is not plotted in FIG.
The impedance is a value measured at a frequency in the range of 0.1 Hz to 8 MHz in dry argon gas using a Solartron product number 1260 as a measuring instrument.

The following can be understood from FIG.
The larger the absolute value | Z | of the impedance, the higher the resistance (lower conductivity), and the smaller the impedance, the lower the resistance (high conductivity). In addition, in the frequency range where the absolute value | Z | of the constant impedance is shown, ion movement corresponding to the frequency occurs. In this range, the higher the frequency, the faster the ion conduction, that is, the higher the conductivity. It will be. In particular,
(1) Glass ceramic pellets are shown to have lower resistance than any other pellet at all frequencies, and can provide an electrolyte layer with higher conductivity.
(2) The frequency region showing the absolute value | Z | of almost constant impedance is within the range of 10 ⁴ to 10 ⁷ Hz for the glass ceramic pellets, and β-alumina (70 ° C.) and (120 ° C.) are 0.1 to 10 Hz. Since the absolute value | Z | of the impedance of the glass ceramic pellet is constant at a higher frequency than β-alumina, high conductivity can be obtained.
(3) In the frequency region where the absolute value | Z | of the substantially constant impedance is shown, the glass ceramic pellets show an absolute value | Z | on the order of 10 ³ , and β-alumina (70 ° C.) and (120 ° C.) are The absolute value | Z | on the order of 10 ⁷ to 10 ⁹ is shown. That is, since the glass ceramic pellet has an absolute value | Z | lower by 10 ⁴ to 10 ⁶ than β-alumina, high electrical conductivity can be obtained.
(4) The absolute value | Z | of the impedance of β-alumina is much larger in the press-molded body at room temperature than in the press-molded body at 70 ° C and 120 ° C. The glass ceramic pellets have absolute values | Z | lower than β-alumina (70 ° C.) and (120 ° C.). Therefore, from the viewpoint that high electrical conductivity can be obtained by pressing at room temperature, the ease of moldability of glass ceramics is extremely advantageous as a solid electrolyte for an all-solid-state secondary battery produced only by press molding. .
I understand that.

Example 4
FIG. 11 shows changes in conductivity with respect to the temperatures of the 75Na ₂ S-25P ₂ S ₅ glass ceramic pellets and 75Na ₂ S-25P ₂ S ₅ glass pellets obtained in Example 3. In FIG. 11, black circles are measurement results for glass ceramics, and white circles are measurement results for glass.
Further, FIG. 11 shows β-alumina (sintered body), Na ₃ Zr ₂ Si ₂ PO ₁₂ (NASICON) (sintered body), 60Na ₂ S-40 (0.9 GeS ₂ .0.1Ga ₂ S ₃ ). In conductivity of glass, Na ₃ PS ₄ crystal (tetragonal), 50Na ₂ S-50SiS ₂ glass, 60Na ₂ S-40GeS ₂ glass and 50Na ₂ S-50P ₂ S ₅ glass pellet The measurement results are also shown.

The pellet of β-alumina (sintered body obtained by firing at 1800 ° C.) Phys. D: Appl. Phys. 10, 1487-1496 (1977).
The pellets of Na ₃ Zr ₂ Si ₂ PO ₁₂ (NASICON) (sintered body) were obtained by the method described in Solid State Ionics, 122, 127-136 (1999).
The glass of 60Na ₂ S-40 (0.9GeS ₂ .0.1Ga ₂ S ₃ ) is obtained by the method described in Solid State Ionics, 178, 1777-1784 (2008).
Na ₃ PS ₄ crystals (tetragonal crystals) Jansen et al. , Journal of Solid State Chemistry, 92 (1992) 110. It was obtained by the method described in 1.
Glass of 50Na ₂ S-50SiS ₂ and glass of 60Na ₂ S-40GeS ₂ and glass of 50Na ₂ S-50P ₂ S ₅ are described in J. Org. Non-Cryst. Solids, 38 & 39, 271-276 (1980).

The following can be seen from FIG.
75Na ₂ S-25P ₂ S ₅ glass ceramic pellets are 75Na ₂ S-25P ₂ S ₅ glass, 60Na ₂ S-40 (0.9 GeS ₂ .0.1Ga ₂ S ₃ ) glass, Na ₃ PS. _It has a higher conductivity than ₄ crystal (tetragonal), 50Na ₂ S-50SiS ₂ glass, 60Na ₂ S-40GeS ₂ glass and 50Na ₂ S-50P ₂ S ₅ glass pellets. .
For example, pellets of the glass ceramics of 75Na ₂ S-25P ₂ S ₅ has a conductivity of 2 × 10 ^-4 Scm ^-1 at room temperature (25 ° C.), having an activation energy of conduction 27KJmol ^-1 ing. Glass pellets 75Na ₂ S-25P ₂ S ₅ has a conductivity of 6 × 10 ^-6 Scm ^-1 at room temperature, and has an activation energy of 47kJmol ^-1. Na ₃ PS ₄ crystal (tetragonal crystal) has a conductivity of 1 × 10 ⁻⁶ Scm ⁻¹ at room temperature.

The Na ₃ Zr ₂ Si ₂ PO ₁₂ (NASICON) sintered body is equivalent to 75Na ₂ S-25P ₂ S ₅ glass ceramic pellets, and the β-alumina sintered body is 75Na ₂ S-25P ₂ S ₅ . The conductivity (10 ⁻³ Scm ⁻¹ ) is higher than that of glass ceramic pellets. However, pellets of β-alumina (sintered body) and Na ₃ Zr ₂ Si ₂ PO ₁₂ (NASICON) (sintered body) need to be sintered at a high temperature of 1000 ° C. or higher, and have an environmental impact. Large and expensive to manufacture. Further, the sintered body becomes brittle due to the high-temperature treatment, and the number of charge / discharge repetitions is reduced. Furthermore, since high temperature treatment is required, the electrode and the electrolyte layer cannot be integrally formed, and the high conductivity can be obtained by the electrolyte layer alone, but the conductivity of the electrode and the electrolyte layer as a whole is lowered.

Claims (5)

General formula _{(I): Na 2 S-} M x S y (M is P, Si, Ge, B, is selected from Al, x and y, depending on the type of M, an integer that gives the stoichiometric ratio An ion-conducting glass ceramic represented by Na ₂ S greater than 67 mol% and less than 80 mol%. The ion conductive glass ceramic according to claim 1, wherein the Na ₂ S—M _x S _y is Na ₂ S—P ₂ S ₅ . It is a manufacturing method of the ion conductive glass ceramics according to claim 1 or 2,
Formula (I): a step of obtaining a glass denoted by the raw material mixture containing Na ₂ S-M _x S give _y Na ₂ S and M _x S _y in predetermined proportions to the mechanical milling process, the glass A method of converting to ion conductive glass ceramics by heat treatment at a temperature equal to or higher than the glass transition point.   The ion-conductive glass according to claim 3, wherein the mechanical milling treatment is performed using a planetary ball mill under conditions of 50 to 600 rotations / minute, 0.1 to 50 hours, and 1 to 100 kWh / kg of a raw material mixture. Manufacturing method of ceramics.   An all-solid material comprising at least a positive electrode, a negative electrode, and a solid electrolyte layer positioned between the positive electrode and the negative electrode, wherein the solid electrolyte layer includes the ion-conductive glass ceramic according to claim 1. Secondary battery.

Images