JPWO2019239890A1 - Amorphous solid electrolyte and all-solid-state secondary battery using it - Google Patents

Abstract

An amorphous electrolyte that can be synthesized at a low temperature and in an extremely short time while having high ionic conductivity, has a low resistance, a high discharge capacity, and is excellent in mass productivity can be obtained. By using a Li2O-P2O5-SO3 system or Li2O-P2O5-SO3-Al2O3 system amorphous solid electrolyte as the first solid electrolyte, it is reduced to lithium at a potential of about 2.0 V, and carbon and the like are released. Although it is reduced by heat treatment under existing conditions, LATP having high ionic conductivity can be used as a second solid electrolyte, and as a result, an all-solid secondary battery having a low resistance value can be obtained. Can be done [Selection diagram] Fig. 9

Description

The present invention relates to an oxide-based solid electrolyte and its use. More specifically, the present invention presents an oxide-based solid electrolyte that can exhibit high conductivity even when pressed at a low temperature, a solid electrolyte that realizes the oxide-based solid electrolyte, and a solid electrolyte layer, a positive electrode layer, a negative electrode layer, and an all-solid secondary containing the same. Regarding batteries.

In recent years, lithium-ion secondary batteries having a high energy density and capable of charging and discharging have been widely used in applications such as power supplies for electric vehicles and power supplies for mobile terminals.
Most of the lithium ion secondary batteries currently on the market have a high energy density, so that a liquid electrolyte (electrolyte solution) such as an organic solvent is generally used. This electrolytic solution is used by dissolving a lithium salt in an aprotic organic solvent such as a carbonic acid ester or a cyclic ester.

However, in a lithium ion secondary battery using a liquid electrolyte (electrolyte solution), there is a risk that the electrolyte solution leaks out. Further, an organic solvent generally used for an electrolytic solution is a flammable substance, and there is a problem that it is not preferable in terms of safety.

Therefore, it has been proposed to use a solid electrolyte instead of a liquid electrolyte (electrolyte) such as an organic solvent. In addition, the development of an all-solid-state secondary battery in which a solid electrolyte is used as the electrolyte and other components are also made of solid is underway.

All-solid-state secondary batteries are classified into sulfide-based and oxide-based batteries according to the electrolyte used. In _{sulfide, 95 (0.6Li 2 S · 0.4SiS} 2) · 5Li 4 SiO 4 and βLi ₃ PS _{4 etc., Li 1 + x Ti 2-} x Al x P 3 of the NASICON structure of oxide-based _{O 12} (X = 0.1-0.4) and Li ₇ La ₃ Zr ₂ O _{12 having a} garnet structure are used as the solid electrolyte. One of the major problems is interface formation, and as one method of solving the problem, interface formation is promoted by mixing ionic conductive glass, whether it is sulfide-based or oxide-based. Or in the oxide-based _{Li 1 + x Ge 2-x} Al x P 3 O 12 ceramic easily fired properties like are used.
In the solid electrolyte of the all-solid-state secondary battery described in Document 1, Li ₂ O-Al ₂ O _3- P ₂ O ₅ type glass is used, and a pressure of 200 MPa is applied at 600 ° C., which is the temperature at which the glass melts. It is sintered. Since the sintering temperature is still high, there is a problem that the electrode active material reacts with the solid electrolyte to reduce the discharge capacity.
The solid electrolyte described in Document 2 is a solid electrolyte of (100-x) Li ₃ BO ₃ · xLi ₂ SO ₄ (x = 0 to 100) made into a glass by mechanical milling, and has a low temperature of 255 ° C., 360 MPa, and 4 hours. However, it is partially crystallized by high pressure and long-term heat treatment to form a solid electrolyte of ^{1 × 10-5 S / cm.} High pressure and long heat treatment are required, leaving doubts about mass productivity.
The solid electrolyte described in Document 3 is obtained _{by molding a powder of Li 1.5} Al _0.5 Ge _1.5 (PO ₄ ) ₃ with a mold and then firing it at 800 ° C. Since no glass electrolyte is used, the reaction temperature is set high, but there is still a problem that the ^{resistance value is as high as 3 × 10-7 S / cm.}

Japanese Patent Application Laid-Open No. 2014-60084 JP 2015-176854 JP-A-2007-258165

The present invention solves the above-mentioned problems, and provides an amorphous electrolyte that has high ionic conductivity, can be synthesized at a low temperature and in an extremely short time, has low resistance, has a high discharge capacity, and is excellent in mass productivity. It is an object of the present invention to provide an all-solid-state secondary battery that can be synthesized by using it in a short time heat treatment.

As a result of intensive test and research in order to solve the above problems, the present inventor has Li ₂ O-P ₂ O _5- SO ₃ system or Li ₂ O-P _{2 as a solid electrolyte used in an all-solid-state secondary battery.} By using the O _5- SO _3- Al ₂ O ₃ system amorphous solid electrolyte as the first solid electrolyte, the all-solid secondary is performed at a lower temperature and in a shorter time than the amorphous solid electrolytes used so far. We have found that it is possible to form the interface of a battery. Further, by using a Li ₂ O-P ₂ O _5- SO ₃ system or a Li ₂ O-P ₂ O _5- SO _3- Al ₂ O ₃ system amorphous solid electrolyte, a solid electrolyte having low reduction resistance can be used. some _{Li 1 + x + y Al x} Ti 2-x P 3-y Si y O 12 ( referred to as LATP) on a total solids in the secondary battery, will be able to be used as the second solid electrolyte, low resistance electrolyte It has also been found that membranes and all-solid-state secondary batteries can be formed. Further, a high discharge capacity can be suppressed decomposition of the active material of the positive electrode layer and negative electrode layer even when a reduction resistant high _{Li 1 + x + y Al x} Zr 2-x P 3-y Si y O 12 ( referred to as LAZP) It has become possible to maintain the battery, and it has been found that an all-solid-state secondary battery having a high energy density can be synthesized, and the present invention has been completed.
That is, according to the present invention, the following all-solid-state secondary battery is provided.

According to the present invention, _{an amorphous solid electrolyte of Li 2} O-P ₂ O _5- SO ₃ system or Li ₂ O-P ₂ O _5- SO _3- Al ₂ O ₃ system is used as the first solid electrolyte. As a result, it is reduced to lithium at a potential of about 2.0 V, and it is reduced by heat treatment under the condition that carbon or the like is present. However, LATP having high ionic conductivity is used as the second solid electrolyte. As a result, an all-solid-state secondary battery having a low resistance value can be obtained. Furthermore, even when the reduction-resistant LAZP is used as the second solid electrolyte, the heat treatment temperature can be lowered, the decomposition of the active material in the positive electrode layer and the negative electrode layer can be suppressed, and an all-solid-state secondary battery having a high energy density can be obtained. Obtainable.

This is the result of the thermogravimetric / differential thermal measurement of Comparative Example 1. This is the result of the thermogravimetric / differential thermal measurement of Comparative Example 2. It is a thermogravimetric / differential thermal measurement result of Example 1. It is a thermogravimetric / differential thermal measurement result of Example 2. It is a thermogravimetric / differential thermal measurement result of Example 3. It is the AC impedance measurement result of Example 1. It is the AC impedance measurement result of Example 19. It is a figure of the heat treatment temperature dependence measurement result of the heat treatment temperature dependence of Comparative Examples 4 to 8 and Examples 15 to 21. (Solid line: Amorphous solid electrolyte of Example 2 is used as the first solid electrolyte, broken line: Amorphous solid electrolyte of Comparative Example 2 is used as the first solid electrolyte) It is the charge / discharge measurement result of Example 26 (solid line: charge curve, broken line: discharge curve). It is the charge / discharge measurement result of Example 14 (solid line: charge curve, broken line: discharge curve).

Hereinafter, embodiments of the all-solid-state secondary battery of the present invention will be described in detail, but the present invention is not limited to the following embodiments, and appropriate modifications are made within the scope of the object of the present invention. Can be carried out. It should be noted that the description may be omitted as appropriate for the parts where the explanations are duplicated, but the gist of the invention is not limited.

(Amorphous solid electrolyte)
The first solid electrolyte used in the present invention is a Li ₂ O-P ₂ O _5- SO ₃ system or Li ₂ O-P ₂ O _5- SO _3- Al ₂ O ₃ system amorphous solid electrolyte. (Glass or amorphous).
Although not particularly limited, molding by a water-cooled casting method, more preferably a twin-roller quenching method, and most preferably a casting method is preferable in terms of mass productivity.
The Li ₂ O component is an essential component necessary for developing lithium ion conductivity. When it is contained in an oxide equivalent composition of 40 mol% or more, the Li ion conductivity is 1 × 10 ^-10 S / cm or more at room temperature. Therefore, _{the content of Li 2} O is preferably 40 mol% or more, more preferably 45 mol% or more, still more preferably 50 mol% or more. On the other hand, the Li ₂ O component is also a factor for stabilizing the crystal state that lowers the conductivity of the glass electrolyte, and if it is too large, it tends to crystallize. Therefore, it is preferably 70 mol% or less, more preferably 58 mol% or less, and most preferably 57 mol% or less.

The P ₂ O ₅ component is an essential component necessary for the solid electrolyte to become amorphous. _{Similarly, since the vitrification range for Li 2} O is wider than that of _{B 2} O ₃ , which is a glass-forming oxide that can be expected to have a low melting point, it is easy to form a glass having stable high ionic conductivity at a lower ratio. _{In particular, it has good compatibility with SO 3} , which is a component for lowering the melting point, and can lower the melting point and Tg. Therefore, _{the content of P 2} O ₅ is preferably 20 mol%, more preferably 22 mol%, and most preferably 25 mol% or more. On the other hand, if the amount of the P ₂ O ₅ component is too large, other components will not enter and the function of lithium ion conduction will be impaired. Therefore, the content is preferably 50 mol% or less, more preferably 45 mol% or less, and most preferably 40 mol% or less.

The SO ₃ component is an essential component necessary for lowering the melting point or lowering the Tg of the amorphous solid electrolyte. If it is 1 mol% or more in terms of oxide, the melting point or Tg of the amorphous solid electrolyte is lowered. Further, since the ionic conductivity of the crystal containing SO3 is higher than that of other glass electrolytes crystallized, it is possible to suppress an increase in resistance due to the crystallization of the glass electrolyte even if it is crystallized by firing or the like.
Therefore, _{the content of SO 3} is preferably 1 mol% or more, more preferably 3 mol% or more, and most preferably 5 mol% or more. On the other hand, since the SO _{3 component may release SO 3} which is a toxic gas during glass synthesis, it is preferably 30 mol% or less, more preferably 25 mol% or less, and most preferably 20 mol% or less.

The Al ₂ O ₃ component is an optional component that improves the water resistance and lithium ion conductivity of the amorphous solid electrolyte. Water resistance and ionic conductivity are improved by containing more than 0% in terms of oxide. Therefore, _{the component of Al 2} O ₃ is preferably more than 0 mol%, more preferably 0.5 mol% or more, still more preferably 1 mol% or more, and most preferably 2 mol% or more. On the other hand, _{if the content of the Al 2} O ₃ component is high, it becomes a factor that stabilizes the crystalline state of the amorphous electrolyte, and if the content is too high, it is easy to crystallize and it is difficult to obtain the solid electrolyte in the amorphous state. Become. Therefore, _{the content of the Al 2} O ₃ component is preferably 10 mol% or less, more preferably 8 mol% or less, and most preferably 6 mol% or less. Here, water resistance is applied not only to water but also to polar solvents such as alcohol, and is an important factor in the battery manufacturing process such as sheet molding.

Since the composition of the amorphous (or glass) composition of the present invention is expressed in mol% with respect to the total amount of the amorphous (or glass) of the oxide-equivalent composition, it can be directly expressed in the description of% by weight. However, the composition by weight ratio display of each component present in the solid electrolyte satisfying the various properties required in the present invention generally takes the following value in terms of weight ratio.
Li = 5-17% by weight and / or P = 17-40% by weight and / or S = 1-15% by weight and / or O = 55-58% by weight

Since the composition of the amorphous (or glass) composition of the present invention is represented by mol% of the total amorphous (or glass) mass of the oxide-equivalent composition, it can be directly expressed in the description of the molar ratio. However, the composition by molar ratio display of each component present in the solid electrolyte satisfying the various properties required in the present invention generally takes the following value in terms of weight ratio.
Li = 15-36 mol% and / or P = 9-20 mol% and / or S = 1-8 mol% and / or O = 53-65 mol% in molar ratio

Since the composition of the amorphous (or glass) composition of the present invention is expressed in mol% with respect to the total amount of the amorphous (or glass) of the oxide-equivalent composition, it can be directly expressed in the description of% by weight. However, the composition by weight ratio display of each component present in the solid electrolyte satisfying the various properties required in the present invention generally takes the following value in terms of weight ratio.
By weight ratio Li = 5 to 17% by weight and / or P = 17 to 40% by weight and / or S = 1 to 15% by weight and / or Al = more than 0 to 6.5% by weight and / or O = 55 to 5 58% by weight

Since the composition of the amorphous (or glass) composition of the present invention is represented by mol% of the total amorphous (or glass) mass of the oxide-equivalent composition, it can be directly expressed in the description of the molar ratio. However, the composition by molar ratio display of each component present in the solid electrolyte satisfying the various properties required in the present invention generally takes the following value in terms of weight ratio.
Li = 15-36 mol% and / or P = 9-20 mol% and / or S = 1-8 mol% and / or Al = more than 0-5 mol% and / or O = 53-65 mol% in molar ratio

(Negative electrode layer)
The negative electrode layer in the all-solid secondary battery of the present invention includes at least one or more negative electrode active material, an amorphous electrolyte as the first solid electrolyte, a crystalline solid electrolyte or a glass ceramics solid electrolyte as the second solid electrolyte, and the like. It is preferably a sintered material containing a conductive auxiliary agent.
The type of the negative electrode active material of the negative electrode layer is not limited. As the negative electrode active material of the present invention, _{transition metal oxides such as TiO 2} , Nb ₂ O ₃ , and WO ₃ or solid solutions thereof, Li ₄ Ti ₅ O ₁₂ , and Li ₂ Ti ₂ O ₄ are preferable.
The content of the negative electrode active material with respect to the total mass of the negative electrode layer material is preferably 10% by mass to 60% by mass. In particular, by setting this content to 10% by mass or more, the battery capacity of the all-solid-state secondary battery can be increased. Therefore, the content of the negative electrode active material is preferably 10% by mass or more, more preferably 18% by mass or more. On the other hand, by setting this content to 60% by mass or less, it is possible to easily secure the ionic conductivity of the electrode layer. Therefore, the content of the negative electrode active material is preferably 60% by mass or less, preferably 50% by mass or less, and more preferably 35% by mass or less.

The composition of the negative electrode active material described in the present invention can be confirmed by ICP emission spectroscopic analysis for the Li component. In addition, other compositions can be confirmed by fluorescent X-ray analysis measurement. Further, when dispersed in the electrode, it can be analyzed by EDX measurement of a transmission electron microscope or the like. In that case, since there is an analytical difference in the Li component and the amount of Li is unknown because it is a negative electrode active material, it can be estimated from the balance of valences of other compositions.

When the content of the amorphous solid electrolyte, which is the first solid electrolyte, with respect to the total mass of the negative electrode layer material is 2% by mass or more, a lithium ion conductive interface can be formed. Further, the amorphous solid electrolyte is a component that increases the density of the negative electrode layer and increases the energy density per volume. Therefore, the content of the amorphous solid electrolyte is preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 4% by mass or more, and particularly preferably 5% by mass or more. Further, the amorphous solid electrolyte may be crystallized as long as ionic conductive crystals are precipitated in the process of heat treatment.
On the other hand, by reducing the content of the amorphous solid electrolyte, which is the first solid electrolyte, to 60% by mass or less with respect to the total mass of the negative electrode layer material, the content is lower than that of the crystalline electrolyte, which is the second solid electrolyte. It is possible to suppress a decrease in lithium ion conductivity due to the excessive presence of an amorphous solid electrolyte having lithium ion conductivity. Further, since the electron conduction in the negative electrode layer is formed by the electron transfer generated by the contact or bonding between the conductive aids, the electron conduction when the contact between the conductive aids is hindered by the amorphous solid electrolyte having no electron conductivity. Resistance increases. Therefore, it is possible to suppress a decrease in electron conductivity due to the excessive presence of an amorphous solid electrolyte having no electron conductivity. Therefore, the content of the glass electrolyte is preferably 60% by mass or less, more preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less.

The crystalline solid electrolyte, which is the second solid electrolyte of the negative electrode layer material of the present invention, is not particularly limited, but is preferably a lithium-containing phosphoric acid compound having a rhombic crystal system. Its chemical formula is represented by _{Li x M '2 P 3 O} 12 (X = 1~1.7). Here, M'is one or more elements selected from the group consisting of Zr, Ti, Fe, Mn, Co, Cr, Ca, Mg, Sr, Y, Sc, Sn, La, Ge, Nb, and Al. .. Further, a part of P may be replaced with Si or B, and a part of O may be replaced with F, Cl or the like. For example, Li _1.15 Zr _1.85 Al _0.15 Si _0.05 P _2.95 O ₁₂ , Li _1.2 Ti _1.8 Al _0.1 Ge _0.1 Si _0.05 P _2.95 O _{12 and the} like can be used. In addition, materials having different compositions may be mixed or combined. The surface may be coated with a glass electrolyte or the like. Alternatively, glass ceramics that precipitate the crystal phase of the lithium-containing phosphoric acid compound having a NASICON type structure by heat treatment may be used. _{Here, the blending ratio of Li 2} O in the glass ceramics is preferably 8% by mass or less in terms of oxide. Even if it is not a NASICON type structure, it is composed of Li, La, Mg, Ca, Fe, Co, Cr, Mn, Ti, Zr, Sn, Y, Sc, P, Si, O, In, Nb, and F. A solid electrolyte having a perovskite type, garnet type, β-Fe ₂ (SO ₄ ) _{type 3} crystal structure and conducting Li ions at 1 × ^{10-5 S / cm or more at room temperature may be used.} Moreover, you may mix the said electrolyte.
Summarizing the above, the second solid electrolyte of the electrolyte layer material of the present invention is Li, Zr, Ti, Sn, Si, Ge, Sc, Y, La, Nb, Al, Ca, Mg, Fe, Mn, Co. , Cr, O, P, B, F, Cl, In, lithium-containing phosphoric acid compound containing rhombic crystal system, NASICON structure, perovskite structure, LISION structure, garnet structure, β-Fe ₂ ( SO ₄ ) One or more crystalline solid electrolytes or glass ceramics showing a type _{3 structure.}

As the conductive auxiliary agent of the negative electrode layer material of the present invention, a material having electron conductivity such as carbon, graphite, carbon nanotube, copper, aluminum alloy, zinc alloy, silver and ruthenium can be used. Different materials may be mixed or combined.
The content of the conductive auxiliary agent with respect to the total mass of the negative electrode layer material is preferably 5% by mass to 30% by mass, although it depends on the type of the conductive auxiliary agent.
In particular, when the content is 5% by mass or more, the electron conduction network formed by the conductive auxiliary agent can be easily secured, so that the charge / discharge characteristics of the battery and the battery capacity can be further improved. Therefore, the total content of the conductive auxiliary agent in the negative electrode layer is preferably 5% by mass or more, more preferably 7% by mass or more, and further preferably 8% by mass or more.
On the other hand, when the content is 30% by mass or less, the content of the negative electrode active material contained in the negative electrode layer is increased, so that the energy density of the all-solid secondary battery can be increased. Therefore, the content of the conductive auxiliary agent in the negative electrode layer is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 15% by mass or less.

(Positive electrode layer)
The positive electrode layer in the all-solid secondary battery of the present invention is composed of a positive electrode active material, an amorphous solid electrolyte as the first solid electrolyte of lithium ion conductivity, and a crystalline electrolyte or a glass ceramic electrolyte as the second solid electrolyte. It is preferably obtained by sintering a material containing at least one and a conductive auxiliary agent.
The type of positive electrode active material in the positive electrode layer is not limited. The positive electrode active material of the present invention is LiRPO ₄ having an olivine structure, and R is one or more of Fe, Co, Mn, Ni, and Zr, and a part thereof may be replaced with Al or the like. Further, a part of P may be replaced with Si or B. A part of O may be replaced with F. _{Further, using LiMn 2} O ₄ having a spinel structure, _{LiCo 1/3} Ni _1/3 Mn _1/3 O _{2 of} a layered oxide, LiNi _1/2 Mn _1/2 O ₂ , LiNiO ₂ , LiCoO _{2 and the} like. May be good. The positive electrode active material contains Li, but when Li in the positive electrode active material moves to the electrolyte material side during firing, oxygen in the positive electrode active material is released to balance the charge, and the positive electrode active material becomes A phenomenon of decomposition into an oxide containing no Li occurs. When this phenomenon occurs, the function as a positive electrode active material is remarkably lowered, and the discharge capacity is lowered. On the other hand, if oxygen in the crystal structure of the positive electrode active material is strongly bonded to other elements, it becomes difficult for oxygen in the lattice to be released, and Li in the positive electrode active material is placed on the electrolyte side in order to balance the charges. It becomes difficult to release the charge, and the decomposition into oxides containing no Li can be suppressed and the discharge capacity can be maintained in a high state. Therefore, the most preferable is an olivine structure in which oxygen in the positive electrode active material is strongly bonded to phosphorus. _{Next, LiMn 2} O ₄ having a spinel structure is preferable. It is preferably a layered oxide such as LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _1/2 Mn _1/2 O ₂ , LiNiO ₂ , and LiCoO ₂ .
The content of the positive electrode active material with respect to the total mass of the positive electrode layer material is preferably 10% by mass to 60% by mass. In particular, by setting this content to 10% by mass or more, the battery capacity of the all-solid-state secondary battery can be increased. Therefore, the content of the positive electrode active material is preferably 10% by mass or more, more preferably 18% by mass or more. On the other hand, by setting this content to 60% by mass or less, it is possible to easily secure the ionic conductivity of the electrode layer. Therefore, the content of the positive electrode active material is preferably 60% by mass or less, preferably 50% by mass or less, and more preferably 35% by mass or less.

When the content of the amorphous solid electrolyte, which is the first solid electrolyte, with respect to the total mass of the positive electrode layer material is 2% by mass or more, a lithium ion conductive interface can be formed. The amorphous solid electrolyte, which is the first solid electrolyte, is a component that softens and melts to increase the density of the positive electrode layer and increase the energy density per volume. Therefore, the content of the amorphous solid electrolyte, which is the first solid electrolyte, is preferably 2% by mass or more, more preferably 3% by mass or more, still more preferably 4% by mass or more, and particularly preferably 5% by mass or more. To do.
On the other hand, by reducing the content of the amorphous solid electrolyte, which is the first solid electrolyte, to 60% by mass or less with respect to the total mass of the positive electrode layer material, lithium is lower than that of the crystalline electrolyte, which is the second solid electrolyte. The decrease in lithium ion conductivity due to the excessive presence of the amorphous solid electrolyte, which is the first solid electrolyte of ionic conductivity, can be suppressed. Further, since the electron conduction in the positive electrode layer is formed by the electron transfer generated by the contact or bonding between the conductive aids, if the contact between the conductive aids is hindered by the glass electrolyte having no electron conductivity, the resistance of the electron conduction increases. It gets higher. Therefore, it is possible to suppress a decrease in electron conductivity due to the excessive presence of the amorphous solid electrolyte, which is the first solid electrolyte having no electron conductivity. Therefore, the content of the amorphous solid electrolyte, which is the first solid electrolyte, is preferably 60% by mass or less, more preferably 50% by mass or less, more preferably 40% by mass or less, still more preferably 30% by mass or less. To do.

The crystalline solid electrolyte or the glass-ceramic electrolyte, which is the second solid electrolyte of the positive electrode layer material of the present invention, is not particularly limited, but is preferably a lithium-containing phosphoric acid compound containing a rhombic crystal system. Its chemical formula is represented by Li _x M " ₂ P ₃ O ₁₂ (X = 1-1.7), where M" is Zr, Ti, Fe, Mn, Co, Cr, Ca, Mg, Sr, It is one or more elements selected from the group consisting of Y, Sc, Sn, La, Ge, Nb, and Al. Further, a part of P may be replaced with Si or B, and a part of O may be replaced with F, Cl or the like. For example, Li _1.15 Ti _1.85 Al _0.15 Si _0.05 P _2.95 O ₁₂ , Li _1.2 Ti _1.8 Al _0.1 Ge _0.1 Si _0.05 P _2.95 O ₁₂ , Li _1.2 Fe _0.2 Ti _1.8 P ₃ O _{12 and the} like can be used. In addition, materials having different compositions may be mixed or combined. The surface may be coated with an amorphous electrolyte or the like. Alternatively, glass ceramics that precipitate the crystal phase of the lithium-containing phosphoric acid compound containing crystals having a NASICON type structure by heat treatment may be used. For example, LICGC ^TM manufactured by O'Hara may be used. _{Here, the blending ratio of Li 2} O in the glass ceramics is preferably 8% by mass or less in terms of oxide. Even if it is not a NASICON type structure, it is composed of Li, La, Mg, Ca, Fe, Co, Cr, Mn, Ti, Zr, Sn, Y, Sc, P, Si, O, In, Nb, and F. A solid electrolyte having a perovskite type, garnet type, β-Fe ₂ (SO ₄ ) _{type 3} crystal structure and conducting Li ions at 1 × ^10-5 S / cm or more at room temperature may be used. Moreover, you may mix the said electrolyte.
Summarizing the above, the second solid electrolyte of the positive electrode layer material of the present invention is Li, Zr, Ti, Sn, Si, Ge, Sc, Y, La, Nb, Al, Ca, Mg, Fe, Mn, Co. , Cr, O, P, B, F, Cl, In, lithium-containing phosphoric acid compound containing rhombic crystal system, NASICON structure, perovskite structure, LISION structure, garnet structure, β-Fe ₂ ( SO ₄ ) One or more crystalline solid electrolytes or glass ceramics showing a type _{3 structure.}

The content of the crystalline solid electrolyte, which is the second solid electrolyte having lithium conductivity, is preferably 30% by mass to 80% by mass with respect to the total mass of the positive electrode layer material.
In particular, when the content is set to 30% by mass or more, the movement path of lithium ions formed by the amorphous solid electrolyte, which is the first solid electrolyte, can be easily secured, so that the charge / discharge characteristics of the battery and the battery can be secured. The capacity can be increased more easily. Therefore, the total content of the lithium conductive second solid electrolyte in the electrode layer is preferably 30% by mass or more, more preferably 45% by mass or more, and further preferably 55% by mass or more.
On the other hand, when the content is 80% by mass or less, the content of the positive electrode active material contained in the positive electrode layer is increased, so that the energy density of the all-solid secondary battery can be increased. Therefore, the content of the lithium conductive second solid electrolyte in the positive electrode layer is preferably 80% by mass, more preferably 75% by mass or less, more preferably 70% by mass or less, still more preferably 65% by mass or less. To do.
As the conductive auxiliary agent of the positive electrode layer material of the present invention, a material having electron conductivity such as carbon, graphite, carbon nanotubes, aluminum alloy, zinc alloy, silver and ruthenium can be used. Different materials may be mixed or combined.
The content of the conductive auxiliary agent with respect to the total mass of the positive electrode layer material depends on the type of the conductive auxiliary agent, but is preferably 5% by mass to 30% by mass.
In particular, when the content is 5% by mass or more, the electron conduction network formed by the conductive auxiliary agent can be easily secured, so that the charge / discharge characteristics of the battery and the battery capacity can be further improved. Therefore, the total content of the conductive auxiliary agent in the positive electrode layer is preferably 5% by mass or more, more preferably 7% by mass or more, and further preferably 8% by mass or more.
On the other hand, when the content is 30% by mass or less, the content of the positive electrode active material contained in the positive electrode layer is increased, so that the energy density of the all-solid secondary battery can be increased. Therefore, the content of the conductive auxiliary agent in the positive electrode layer is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 15% by mass or less.

(Solid electrolyte layer)
The solid electrolyte layer in the all-solid secondary battery of the present invention is a material containing at least one of an amorphous solid electrolyte as a first solid electrolyte, a crystalline solid electrolyte as a second solid electrolyte, or a glass ceramic electrolyte. Is preferably sintered.

When the content of the amorphous solid electrolyte as the first solid electrolyte with respect to the total mass of the solid electrolyte layer material is 3% by mass or more, the amorphous solid electrolyte is a crystalline solid as the second solid electrolyte. It can reach the electrolyte interface and increase the ionic conductivity of the solid electrolyte layer. Further, since the density of the solid electrolyte layer can be increased, the strength of the all-solid secondary battery can also be increased. If it is less than 3% by mass, the ionic conductivity of the solid electrolyte layer cannot be increased. Therefore, the content of the amorphous electrolyte, which is the first solid electrolyte, in the solid electrolyte layer is preferably 3% by mass or more, more preferably 4% by mass or more, still more preferably 4.5% by mass or more, and particularly preferably. Is 5% by mass or more.
On the other hand, when the content of the amorphous solid electrolyte, which is the first solid electrolyte, exceeds 90% by mass, it is the first solid electrolyte that connects the crystalline solid electrolytes, which are the second solid electrolytes. The film thickness of the crystalline solid electrolyte becomes thicker, and the distance through which the lithium ions pass through the amorphous solid electrolyte becomes longer. The influence of the conductivity of the amorphous solid electrolyte, which has a lower conductivity than that of the crystalline electrolyte, becomes stronger, and as a result, the ionic conductivity decreases. Therefore, by reducing the content of the amorphous solid electrolyte, which is the first solid electrolyte, to 90% by mass or less, it is possible to prevent the above-mentioned decrease in ionic conductivity. Therefore, the content of the amorphous solid electrolyte is preferably less than 90% by mass, preferably 80% by mass or less, more preferably 70% by mass or less, and further preferably 60% by mass or less.

The type of the crystalline solid electrolyte, which is the second solid electrolyte contained in the solid electrolyte layer material, is not limited. The crystalline solid electrolyte, which is the second solid electrolyte of the present invention, is a lithium-containing phosphoric acid compound having a rhombic crystal-based NASICON type structure, and has a chemical formula of Li _x L ₂ P ₃ O ₁₂ (X = 1-1). It is represented by .7). Here, L is one or more elements selected from the group consisting of Zr, Ti, Fe, Mn, Co, Ca, Mg, Sr, Y, La, Ge, Nb, and Al. Further, a part of P may be replaced with Si or B, and a part of O may be replaced with F, Cl or the like. For example, Li _1.2 Zr _1.85 Al _0.15 Si _0.05 P _2.95 O ₁₂ and Li _1.2 Zr _1.85 Al _0.1 Ti _0.05 Si _0.05 O ₁₂ are used. be able to. In addition, materials having different compositions may be mixed or combined. A lithium ion conductor different from the NASICON type, a solid electrolyte having a perovskite structure such as _{La 0.57} Li _0.29 TiO ₃ (referred to as LLTO), and a cube such as _{Li 7} La ₃ Zr ₂ O _{12 (LLZO).} Solid electrolyte with crystal garnet structure, β-Fe ₂ (SO ₄ ) _{type 3} solid electrolyte _{such as Li 3} In ₂ (PO ₄ ) ₃ , Lithium type solid electrolyte such as _{Li 3.5} Si _0.5 O ₄ Etc. may be used. The surface of any ceramic electrolyte may be coated with a glass electrolyte or the like.
Summarizing the above, the second solid electrolyte of the electrolyte layer material of the present invention is Li, Zr, Ti, Sn, Si, Ge, Sc, Y, La, Nb, Al, Ca, Mg, Fe, Mn, Co. , Cr, O, P, B, F, Cl, In, lithium-containing phosphoric acid compound containing rhombic crystal system, NASICON structure, perovskite structure, LISION structure, garnet structure, β-Fe ₂ ( SO ₄ ) One or more crystalline solid electrolytes or glass ceramics showing a type _{3 structure.}

It is preferable that the content of the crystalline solid electrolyte, which is the second solid electrolyte having lithium ion conductivity, is 98% by mass or less with respect to the total mass of the solid electrolyte layer material. As a result, the amorphous solid electrolyte, which is the first solid electrolyte, can exist, and the interface and the path through which lithium ions are conducted are easily formed in the solid electrolyte layer. Therefore, the lithium ion conductivity of the solid electrolyte layer is improved. Can be enhanced.
On the other hand, the lower limit of the content of the lithium ion conductive crystalline solid electrolyte is not particularly limited and may be 0% by mass.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.
As the description of the present invention, the synthesis and evaluation of the amorphous solid electrolyte which is the first solid electrolyte, the mixing / firing and evaluation of the amorphous solid electrolyte which is the first solid electrolyte and the second solid electrolyte, and the first. Three solid electrolytes, which are a mixture of an amorphous solid electrolyte, which is one solid electrolyte, and a crystalline solid electrolyte, which is a second solid electrolyte, are evaluated for adaptation to an all-solid secondary battery.

<Preparation of amorphous solid electrolyte, which is the first solid electrolyte>
Table 1 shows the charged composition of the amorphous solid electrolyte, which is the first synthesized solid electrolyte. The raw material _{LiPO 3, Li 3 PO 4,} Li 2 SO 4 · 5H 2 O, Al (PO 3) 3, H 3 PO 4, Li 2 CO 3, H 3 BO 3, using a synthesized stoichiometric did. A platinum crucible was used for melting, and the melting temperature was set to 600 ° C to 1100 ° C. The melting time was 30 minutes to 2 hours. The sample for which the conductivity was measured was obtained by sandwiching it between heat-resistant steel cast plates and forming it into a plate shape. Other samples were obtained by casting on heat resistant steel. Since the SO ₃ component is likely to volatilize, the composition _Al 2 _{O 3} component is large, once crushed components other than SO ₃ after melting after molding at a high temperature, the _{Li 2 SO} 4 · 5H 2 O is a SO ₃ component In addition, it was melted. Except for Comparative Example 3, all of them were stable amorphous (glass) and did not crystallize. In Comparative Example 3, a glassy sample could not be obtained. Table 2 shows the analysis results of the amorphous solid electrolyte after preparation. The measurement method was carried out using an ICP emission spectroscopic analyzer (manufactured by Agilent Technologies, Inc .: ICP-OES 720-ES).

<Evaluation of amorphous solid electrolyte>
The thermal properties of the amorphous solid electrolyte, which is the first synthesized solid electrolyte, were measured by thermogravimetric analysis and differential thermal measurement (TG-DTA2000SA manufactured by Bruker AXS Co., Ltd.). The evaluation results are shown in FIGS. 1 to 5 and Table 3. Compared to Comparative Example 1 and Comparative Example 2 containing no SO _3, 10.0 ° C. In Examples 1-14 Both glass softening point containing SO ₃ (Tg) ~78.4 ℃, a melting point (mp) It was confirmed that the temperature decreased from 14.3 ° C to 192.2 ° C.
The conductivity was calculated and derived from the resistance value obtained by the AC resistance measurement by the AC impedance method, and the thickness and the electrode diameter obtained by the thickness and the electrode area measurement. Gold was used as the blocking electrode used in the AC impedance method. The surface of the plate-shaped sample was polished with 1-propanol as a polishing solution with No. 800 and No. 2000 water-resistant abrasive paper, and a gold electrode was formed on the polished surface by magnetron sputtering (SC701HMC manufactured by Sanyu Electronics). .. The thickness was evaluated using a micrometer, and the electrode diameter was evaluated with a caliper. The AC impedance measurement result of Example 1 is shown in FIG. In each of the results, the point indicated by the arrow in FIG. 6 was read as the resistance value, and the conductivity was calculated from the electrolyte thickness and the area of the gold electrode. Table 3 shows the calculated conductivity values of Comparative Example 1, Comparative Example 2, and Examples 1 to 14. It was confirmed that the conductivity was also improved by about 2 to 10 times as compared with the comparative example.
From the above results, improvement was observed in the conditions necessary for interface formation such as glass softening point, melting point and ionic conductivity.

<Evaluation of conductivity of a mixture of amorphous solid electrolyte, which is the first solid electrolyte, and crystalline solid electrolyte, which is the second solid electrolyte>
Confirm whether the prepared amorphous solid electrolyte, which is the first solid electrolyte, has a function of forming an ionic conductive interface and improving conductivity by mixing with the crystalline solid electrolyte, which is the second solid electrolyte. To this end, an electrolyte membrane was formed by mixing an amorphous solid electrolyte, which is the first solid electrolyte, and a crystalline solid electrolyte, which is the second solid electrolyte, and the conductivity was evaluated by the AC impedance method.

<Preparation of crystalline solid electrolyte, which is the second solid electrolyte>
The second solid electrolytes include Li _1.2 Al _0.15 Zr _1.85 Si _0.05 P _2.95 O ₁₂ (referred to as LAZP _{12) and Li 1.2} Al _{0.15 as NASICON type solid electrolytes.} Ti _1.85 Si _0.05 P _2.95 O ₁₂ (referred to as LATP 12) was used. Further, as the solid electrolyte of perovskite _type, a La _0.5 1Li _{0.34 TiO} 2.94 (referred to as LLTO) as a solid electrolyte of the garnet-type, as a solid electrolyte of LISICON type of _LLZO, Li 3.5 _{Si 0. 5} P _0.5 O ₄ (referred to as LSPO) was used.

<Preparation of crystalline solid electrolyte, which is the second solid electrolyte LATP12>
As one of the crystalline solid electrolytes, which is the second solid electrolyte, highly ionic conductive Li _1.2 Al _0.15 Ti _1.85 Si _0.05 P _2.95 O ₁₂ was prepared. A fine powder _{of LiPO 3} , TiO ₂ , Al (PO ₃ ) ₃ , and SiO ₂ as raw materials _{and a solution of H 3} PO ₄ were mixed in a stoichiometric ratio, and then calcined in a quartz crucible at 1100 ° C. for 5 hours. A mixture of calcined raw materials was pulverized to 106 μm or less with a stamp mill, and pulverized to 1 μm or less with a wet planetary ball mill to obtain a solid electrolyte (hereinafter, this solid electrolyte is referred to as LATP12). The calcined sample is evaluated by a powder X-ray diffractometer (X'Pert-MPD manufactured by Philips), and has a crystal structure similar _{to that of the rhombohedral LiTi 2} (PO ₄ ) _{3 (JCPDS: 35-0754).} It was confirmed.

<Preparation of crystalline solid electrolyte, which is the second solid electrolyte LAZP12>
As one of the solid electrolytes, a reduction-resistant Li _1.2 Al _0.15 Zr _1.85 Si _0.05 P _2.95 O ₁₂ containing no Ti component was prepared. A fine powder _{of LiPO 3} , ZrO ₂ , Al (PO ₃ ) ₃ , and SiO ₂ as raw materials _{and a solution of H 3} PO ₄ were mixed in a stoichiometric ratio, and then calcined on a platinum plate at 1350 ° C. for 1 hour. .. A mixture of calcined raw materials was pulverized to 106 μm or less with a stamp mill, and pulverized to 1 μm or less with a wet planetary ball mill to obtain a reduction-resistant solid electrolyte (hereinafter, this reduction-resistant solid electrolyte is referred to as LAZP12). The obtained sample was evaluated by a powder X-ray diffractometer, and it was confirmed that the crystal structure was similar _{to that of the rhombohedral LiZr 2} (PO ₄ ) _{3 (JCPDS: 084-0998).}

<Crystally solid electrolyte, which is the other second solid electrolyte>
Other crystalline solid electrolytes (La _0.57 Li _0.29 TiO ₃ , Li ₇ La ₃ Zr ₂ O ₁₂ , Li _3.5 Si _0.5 O ₄ ) were purchased from the Institute of High Purity Chemistry.

<Crushing and mixing of samples>
Amorphous solid electrolytes, which are the first solid electrolytes prepared and obtained, and crystalline solid electrolytes, which are the second solid electrolytes, were ground under a nitrogen atmosphere using a stamp mill to a 106 μm mesh path. After mixing so that the amorphous solid electrolyte, which is the first solid electrolyte, is 6% by weight and the crystalline solid electrolyte, which is the second solid electrolyte, is 94% by weight, wetting with a planetary ball mill using 1-propanol as a solvent. Crushed. As for the pulverization conditions of the sample, a particle size distribution measuring device (Mastersizer 3000 manufactured by Malvern) was used to pulverize the sample until the particle size distribution was 2 μm or less at D90 with _{a refractive index equivalent to TiO 2 (2.9), and then the sample was taken out and dried.} I let you. The dried powder was pulverized with a lab miller to 106 μm or less and used as a raw material before firing.

<Molding / firing / evaluation>
0.1 g of the raw material before firing ^{was pressure-molded at 2000 kgf / cm 2 and} then heated to a predetermined temperature to obtain an electrolyte membrane. Both sides of the obtained electrolyte membrane were polished on the surfaces using No. 800 and No. 2000 water resistant abrasive papers. After the polished sample was dried, gold electrodes were formed by sputtering on both sides using magnetron sputtering so as not to cause a short circuit. Impedance was measured using an electrochemical measuring device (SP-300 manufactured by BiO Logical). The amplitude voltage was 10 mV and the measurement temperature was 25 ° C. The measurement frequency was 1 MHz to 0.1 Hz. In each case, the evaluation temperature was 25 ° C. The measurement result of Example 19 is shown in FIG. The film thickness measured with a micrometer was 0.47 mm, and the diameter of the electrode was 0.67 cm. Regarding the estimation of the resistance value, the resistance value corresponding to the arrow portion in FIG. 7 was read from each graph. The measurement results are shown in Table 4 and FIG.

Regarding the amorphous electrolytes of Comparative Examples 2 and 2 and the solid electrolyte membrane using LATP12, the relationship between the heat treatment temperature and the conductivity was confirmed. Table 4 shows the results when the solid electrolyte of Comparative Example 2 was used (Comparative Examples 4 to 8). The product treated at a heat treatment temperature of 600 ° C. (Comparative Example 4) ^{shows a high ionic conductivity of 1.2 × 10 -4} S / cm at room temperature, but when the heat treatment temperature is lowered by 50 ° C. (Comparative Example 6), the ionic conductivity becomes high. It decreased to 3.4 × ^10-5 S / cm. In comparison, it was confirmed that when _{the solid electrolyte of Example 2 to which SO 3} was added was used (Examples 15 to 22), ^{a high ion conduction of 0.2 × 10 -4 S / cm was exhibited from a low temperature of 450 ° C.} did it.
It has extremely high ionic conductivity for an electrolyte membrane constructed by heat treatment in this temperature range. It has not been realized by the glass electrolyte alone or the material obtained by crystallizing the glass electrolyte, and even by using the powder of LATP12 alone having high ionic conductivity, it has not been realized by the heat treatment in this temperature range.
^{As the crystalline solid electrolyte which is the second solid electrolyte, 1.0 × 10-5} S / cm for LLZO having a garnet structure in addition to LATP12 and LAZP12, and 1.0 × 10 for LLTO having a perovskite structure. It was confirmed that even when _{Li 3.5} Si _0.5 O ₄ ^{having a -4} S / cm and LISION structure was ^{used, a high ionic conductivity of 0.7 × 10 -6} S / cm was exhibited. None of LLZO, LLTO and Li _3.5 Si _0.5 O ₄ show ionic conductivity even if the same treatment is performed without mixing the first solid electrolyte, and the second solid electrolyte is an amorphous solid. The effect of the electrolyte was confirmed (Examples 23 to 25).

<Evaluation of all-solid-state secondary battery>
In order to confirm that the amorphous solid electrolyte, which is the first solid electrolyte, functions as the solid electrolyte of the all-solid secondary battery, an all-solid secondary battery was prepared and evaluated. The all-solid-state secondary battery includes a positive electrode layer containing a positive electrode active material, a negative electrode layer containing a negative electrode active material, and an electrolyte layer formed only of an electrolyte. As the electrolyte layer, the mixed electrolyte used in the conductivity measurement was used. The method of synthesizing the positive electrode layer and the negative electrode layer and the method of manufacturing the all-solid-state secondary battery will be described below.

<Preparation of active material powder and preparation of positive electrode layer and negative electrode layer powder>
_{Li 1.5} Fe _0.5 Ti _1.5 P ₃ O ₁₂ (hereinafter referred to as LFTP15) was prepared as a negative electrode active material. _{LiPO 3} , Fe ₂ O ₃ , TiO ₂ , and H ₃ PO ₄ were used as raw materials, mixed in a stoichiometric ratio, placed in a quartz pot, and calcined in the air at 1000 ° C. for 10 hours. The calcined sample was evaluated by a powder X-ray diffractometer, and it was confirmed that the crystal structure was similar _{to that of the rhombohedral LiTi 2} (PO ₄ ) _{3 (JCPDS: 35-0754).}

_{LiMn 0.75} Fe _0.25 PO ₄ (hereinafter referred to as LMFP) was prepared as a positive electrode active material. _{Using LiPO 3} , Fe ₂ O ₃ , and MnO ₃ as raw materials, after mixing in a stoichiometric ratio, mix 5 wt% acetylene black, put it in a graphite crucible and seal it, and in a nitrogen atmosphere furnace with graphite arranged around 800 It was calcined at ° C. for 1 hour. It was confirmed by a powder X-ray diffractometer _{that it was LiMnPO 4} (JCPDS: 77-0178).
Both the negative electrode active material and the positive electrode active material were pulverized with D90 to 0.5 μm or less with a planetary ball mill using 1-propanol as a dispersion medium.
The positive electrode layer and the negative electrode layer were prepared according to the preparation method shown in Table 5, and then mixed with Rentaro Awatori (ARV200 manufactured by Shinky). The YTZ balls were separated, quickly evaporated to dryness, and then crushed with a lab miller to obtain positive electrode layer powder and negative electrode layer powder, respectively.

<All-solid-state secondary battery configuration and evaluation>
After putting 30 mg of the negative electrode layer powder into a φ11 mold, the surface was smoothed by pressing with the weight of the mold itself. Next, 50 mg of electrolyte layer powder was added, and the surface was smoothed again. Finally, the positive electrode layer powder was added and the surface was smoothed, and then the upper mold was fitted. After filling with powder, the temperature was raised to a set temperature after pressure molding at ^{2000 kgf / cm 2, and an all-solid secondary battery was obtained.} The obtained all-solid-state secondary battery was ground to about 200 μm using No. 800 water-resistant abrasive paper in order to suppress a short circuit on the outer circumference. Graphite paste (manufactured by Nippon Graphite) was used for current collection, aluminum foil was used on the positive electrode side, and copper foil was used on the negative electrode side to collect current, and the outside air was blocked by an aluminum laminate pack.
The amorphous solid electrolyte of Example 2 and Comparative Example 2 as the first solid electrolyte, LATP12 as the crystalline solid electrolyte of the second solid electrolyte, LFTP15 as the negative electrode active material, and the positive electrode active material as the negative electrode active material. The charge / discharge characteristics of the all-solid secondary battery at a heat treatment temperature of 500 ° C. are shown in FIG. 9 as Example 26. When the heat treatment temperature was 600 ° C. with the same composition, no charge / discharge characteristics were exhibited under any of the conditions.
In order to confirm the result of not showing charge / discharge characteristics when heat-treated at 600 ° C., a comparatively produced battery (Comparative Example 9) was powdered and electron spin resonance measurement was performed. The device used is an electron spin resonance analyzer (Bruker E500). As a result of the analysis, an increase in the peak of ^{2.5 × 10 18 spins / mg corresponding to several% by weight was confirmed as compared with the untreated sample.} From this, it is considered that Ti in LATP12, which is the second solid electrolyte, was reduced from Ti ^{4+ to Ti 3+} by the reducing atmosphere of carbon dispersed in the positive electrode layer and the negative electrode layer, and LATP12 became electron conductive. Be done. Therefore, it is considered that it was short-circuited and did not show charge / discharge characteristics. Even in the low temperature treatment at 500 ° C. (Example 26), ^{a peak increase of 0.9 × 10 18} spins / mg was confirmed as compared with the untreated product, but since no short-circuit behavior was shown ^{, the reduction of Ti 3+} was networked in the electrolyte membrane. It can be presumed that it has not progressed enough to form.
From the above, it was confirmed that the glass electrolyte shown in the examples enables low-temperature treatment that was not possible until now, and that an all-solid-state secondary battery that can be charged and discharged and has low resistance can be obtained.
When LAZP12, which exhibits higher reduction resistance than LATP12 containing Ti, was used as the electrolyte membrane, it exhibited charge / discharge characteristics even after heat treatment at 600 ° C. It is probable that since LAZP12 does not have a Ti component, short circuit could be suppressed without reduction. In order to measure the resistance value of the manufactured battery, the resistance was measured by the AC impedance method. The results are shown in Table 7. It was confirmed that the cell using LATP12 as the second solid electrolyte had an order of magnitude lower resistance than the cell using LAZP12 as the second solid electrolyte.

Claims (6)

Amorphous solid electrolyte represented by Li ₂ O-P ₂ O _5- SO _3. The composition of Li ₂ O-P ₂ O _5- SO _{3 is Li 2} O = 40 to 70 mol% P ₂ O ₅ = 20 to 50 mol% in terms of oxide-equivalent molar ratio.
SO ₃ = 1 to 30 mol%
The amorphous solid electrolyte according to claim 1. The composition of Li ₂ O-P ₂ O ₅ -SO _3- Al ₂ O ₃ is in terms of oxide-equivalent molar ratio. Li ₂ O = 40 to 70 mol% P ₂ O ₅ = 20 to 50 mol%.
SO ₃ = 1 to 30 mol%
Al ₂ O ₃ = more than 0 to 10 mol%
The amorphous solid electrolyte according to claim 1 or 2. The solid electrolyte according to any one of claims 1 to 3, wherein the amorphous solid electrolyte, which is the first solid electrolyte by weight, is 3 to 15% or 60 to 95%. From 3 or more elements of Li, Zr, Ti, Sn, Si, Ge, Sc, Y, La, Nb, Al, Ca, Mg, Fe, Mn, Co, Cr, O, P, B, F, Cl, In One or more crystalline solid electrolytes showing a lithium-containing phosphoric acid compound containing a rhombic crystal system, a NASICON structure, a perovskite structure, a LISION structure, a garnet structure, and a β-Fe ₂ (SO ₄ ) _{type 3 structure.} An all-solid-state secondary battery in which glass ceramics is mixed as a second solid electrolyte, and the amorphous solid electrolyte according to any one of claims 1 to 4 is mixed as a first solid electrolyte. An all-solid-state secondary battery characterized in that the solid electrolyte according to any one of claims 1 to 5 is used in any one or more of a positive electrode layer, a negative electrode layer, and an electrolyte layer.

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