JP7105055B2 - Anode materials, anodes and batteries - Google Patents

Description

The present invention relates to negative electrode materials, negative electrodes and batteries.

BACKGROUND ART In recent years, lithium-ion secondary batteries, which have high energy density and can be charged and discharged, have been widely used in applications such as power sources for electric vehicles and power sources for mobile terminals.
Many lithium ion secondary batteries currently on the market generally use a liquid electrolyte (electrolytic solution) such as an organic solvent because of their high energy density. This electrolytic solution is used by dissolving a lithium salt in an aprotic organic solvent such as a carbonate ester or a cyclic ester.

However, in a lithium-ion secondary battery using a liquid electrolyte (electrolytic solution), there is a risk that the electrolytic solution may leak. In addition, organic solvents and the like that are commonly used in electrolytic solutions are combustible substances, which poses the problem of being unfavorable in terms of safety.

Therefore, it has been proposed to use a solid electrolyte instead of a liquid electrolyte (electrolytic solution) such as an organic solvent. In addition, development of a solid secondary battery in which a solid electrolyte is used as the electrolyte and other constituent elements are also solid is being developed.

Li _1+x Al _x Ti _2-x P _3-y Si _y O ₁₂ (x=0.1 to 0.5, y=0.1 to 0.3) containing Ti in the solid electrolyte (hereinafter referred to as LATP A solid electrolyte exhibiting a rhombohedral NASICON-type crystal structure such as (hereinafter referred to as LLTO) and a solid electrolyte exhibiting a perovskite-type crystal structure such as (La, Li)TiO ₃ (hereinafter referred to as LLTO) exhibit high ion conductivity at room temperature. It is used in Li _{seawater batteries} , etc., and has been confirmed to have superior properties compared to other electrolytes, such as _high water resistance. It is expected as a solid electrolyte for all-solid-state batteries that can be solved. However, at about 2.0 V relative to Li, Ti in _LATP or _LLTO is reduced and cannot function as an electrolyte at 2.0 V or less. There is a problem that negative electrode materials such as ₅ O ₁₂ (Li vs. 1.5 V) cannot be used and there is no suitable negative electrode material.

Non-Patent Literature "Development and Latest Technology of Metal/Air Secondary Batteries" Edited by Tatsumi Ishihara ISBN978-4-907837-22-8 JP 2007-258165

The present invention solves the above problems, and provides an all-solid battery with low resistance and good cycle characteristics by using a negative electrode material with a high potential that corresponds to a solid electrolyte with high ion conductivity. With the goal.

In order to solve the above problems, the inventors of the present invention have conducted intensive tests and research and found that Li _1+x+y+2z A _z M _x T _2-x-z P _3-y Si _y O ₁₂ as a negative electrode material for use in all-solid-state batteries. (x = 0.1 to 1.0, y = 0 to 0.5, z = 0 to 0.2) (A is one or more selected from Mg and Ca, and M is Fe, Mn, Co, Ni , Cr, Y, Sc, Al, and V, and T is at least one selected from Ti, Zr, Ge, and Sn. It was found that it is possible to charge and discharge at 0 V or more. Further, the present inventors have also found that the cycle characteristics can be improved by optimizing the elements and ratios in Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ , and have completed the present invention.
That is, according to the present invention, the following all-solid-state battery is provided.

According to the present invention, Li _1+x+y+2Z A ZM _x T _{2-x-z P 3-y} Si _y O ₁₂ (x=0.1-1.0, y=0-0.5) with high redox potential , z = 0 to 0.2) as a negative electrode material, it is possible to use LATP as a solid electrolyte, which is reduced to lithium at a potential of about 2.0 V but has high ionic conductivity. As a result, an all-solid-state battery with a low resistance value can be obtained.

Example ₄ It is the result of powder X _- ray _{diffraction measurement} of _{Li1.5Fe0.5Ti1.5P3O12} . Example ₁₅ It is the result of powder X _- ray _{diffraction measurement} of _{Li1.5Fe0.5Zr1.5P3O12} . Example ₄ It is a diagram of charge-discharge evaluation results of a _{Li1.5Fe0.5Ti1.5P3O12 liquid -} based _half -cell. (solid line: charging, dashed line: discharging) Comparative Example 1 FIG. 1 is a diagram showing charge-discharge evaluation of an all-solid-state half-cell of TiO ₂ using a reduction-resistant solid electrolyte containing no Ti component. (solid line: charging, dashed line: discharging) Comparative Example 2 FIG. 2 is a diagram showing charge/discharge evaluation results of a TiO ₂ all-solid-state half-cell using a LATP solid electrolyte. (solid line: charging, dashed line: discharging) FIG. 18 is a diagram showing charge/discharge evaluation results of an all-solid-state half-cell of Li _1.5 Fe _0.5 Ti _1.5 P ₃ O ₁₂ using a reduction-resistant solid electrolyte containing no Ti component. (solid line: charging, dashed line: discharging) Example 19 It is a diagram of the charge-discharge evaluation results of an all-solid-state half-cell of Li _1.5 Fe _0.5 Ti _1.5 P ₃ O ₁₂ using a LATP solid electrolyte. (solid line: charging, dashed line: discharging) Example 36 It is a figure of the charging/discharging evaluation result of an all-solid-state battery. (solid line: charging, dashed line: discharging)

Hereinafter, embodiments of the all-solid-state battery of the present invention will be described in detail, but the present invention is not limited to the following embodiments at all, and can be carried out with appropriate changes within the scope of the purpose of the present invention. can do. It should be noted that descriptions of overlapping descriptions may be omitted as appropriate, but the gist of the invention is not limited.

(glass electrolyte)
The glass electrolyte used in the present invention is Li ₂ OG (G=Al ₂ O ₃ , Nb ₂ O ₅ , Y ₂ O ₃ , SiO ₂ , B ₂ O ₅ , P ₂ O ₅ , V ₂ O ₅ , TeO ₂ , CeO ₂ , GeO ₂ , Bi ₂ O ₃ , etc.), but the lithium concentration is 15% by mass or more in terms of oxide, it is amorphous, and the lithium ion conductivity at room temperature is 1 × 10 There is no particular limitation as long as it is ^-11 S/cm or higher. A basic composition of Li ₂ O—Al ₂ O ₃ —P ₂ O ₅ exhibits particularly excellent characteristics. Unless otherwise specified, the content of each component contained in the glass electrolyte of the present invention is represented by mass % based on oxides. Here, the "composition converted to oxide" is the amount of oxides produced, assuming that the oxides, composite salts, metal fluorides, etc. used as raw materials for the glass electrolyte are all decomposed and changed into oxides when melted. It is a composition in which each component contained in the glass electrolyte is described with the total mass as 100% by mass.

When the positive electrode material or negative electrode material and the solid electrolyte are sintered at a high temperature, Li and transition metals diffuse, causing an increase in internal resistance and a decrease in discharge capacity, and the solid electrolyte, positive electrode material, or negative electrode material becomes a material with no charge-discharge capacity. Side reactions such as decomposition occur. By using the above glass electrolyte, the glass electrolyte softens at a low temperature of about 700° C. or less to form an interface, and an all-solid-state battery can be constructed at a low temperature, thereby suppressing the above side reactions.

(Negative electrode layer)
The negative electrode layer in the all-solid-state battery of the present invention is obtained by sintering a material containing a negative electrode material, at least one of a glass electrolyte, a ceramics electrolyte, or a glass ceramics electrolyte as a lithium ion conductive solid electrolyte, and a conductive aid. is preferably
The content of the negative electrode material with respect to the total mass of the negative electrode layer material is preferably 20% by mass to 90% by mass. In particular, by making this content 20% by mass or more, the battery capacity of the all-solid-state battery can be increased. Therefore, the content of the negative electrode material is preferably 20% by mass or more, more preferably 30% by mass or more. On the other hand, by making this content 90% by mass or less, it is possible to easily ensure electron conduction in the electrode layer. Therefore, the content of the negative electrode material is preferably 90% by mass or less, preferably 70% by mass or less, and more preferably 50% by mass or less.

(negative electrode material)
Before charging Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ (x=0.1-1.0, y=0-0.5, z=0-0.2) preferably have a rhombohedral crystal system.
x is preferably 0.1 or more, more preferably 0.2 or more, and still more preferably 0.2 or more, because the crystal structure is maintained in a rhombohedral system with high ionic conductivity, and charging and discharging are possible by changing the valence. 0.3 or more. On the other hand, if x is too high, the rhombohedral crystal structure will be distorted and the ionic conductivity will decrease. Therefore, x is set to 1.0 or less, more preferably 0.8 or less, and even more preferably 0.7 or less.
y can increase the amount of lithium in the negative electrode material and increase the conductivity. It is preferably 0 or more, more preferably 0.02 or more, more preferably 0.05 or more, and still more preferably 0.08 or more. On the other hand, if y becomes too high, the synthesis temperature rises and the ionic conductivity also decreases. Therefore, y is set to 0.5 or less, more preferably 0.3 or less, and even more preferably 0.2 or less.
z is an optional component capable of stabilizing the crystal structure by keeping the crystal structure in a rhombohedral system with high ion conductivity and not changing the valence. It is preferably 0 or more, more preferably 0.02 or more, more preferably 0.05 or more, still more preferably 0.1 or more. On the other hand, if z is too high, the ionic conductivity of the whole will decrease due to the shared alkali effect if a glass electrolyte or the like is used in the negative electrode layer or the electrolyte layer. Therefore, z should be 0.2 or less, more preferably 0.15 or less, and even more preferably 0.12 or less.

When the Fe component has a chemical composition of Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ and the chemical composition ratio exceeds 0.1, the valence of Fe changes. It is an optional component that can be charged and discharged by Therefore, the Fe content is preferably more than 0.1, more preferably 0.2 or more, still more preferably 0.3 or more, and still more preferably 0.4 or more.
On the other hand, by setting the content of the Fe component to 0.8 or less in terms of chemical composition ratio, the crystal structure can be maintained in the rhombohedral system and can function as an active material. Therefore, the content of the Fe component is preferably 0.8 or less, more preferably 0.7 or less, still more preferably 0.6 or less in chemical composition ratio.
As for the Fe component, Fe ₂ O ₃ , Fe(OH) ₂ , FeCO ₃ or the like can be used as raw materials.

When the Al component contains a chemical composition ratio of more than 0 when the chemical composition is Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ , it has a rhombohedral crystal structure. It is an optional ingredient that can be stabilized. Therefore, the Al content is preferably greater than 0, more preferably 0.02 or more, still more preferably 0.05 or more, and still more preferably 0.1 or more.
On the other hand, by setting the content of the Al component to 0.3 or less in chemical composition ratio, the crystal structure can be maintained in a rhombohedral system while retaining the elements that contribute to charging and discharging, and it can function as an active material. can be done. Therefore, the content of the Al component is preferably 0.3 or less, more preferably 0.25 or less, and still more preferably 0.2 or less in terms of chemical composition ratio.
Al component can use _Al2O3 , Al(OH) _{3 , Al(PO3)3 etc. as} a raw material.

The Y component has a rhombohedral crystal structure when the chemical composition ratio is greater than 0 when the chemical composition is Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ It is an optional ingredient that can be stabilized. Therefore, the Y content is preferably greater than 0, more preferably 0.02 or more, still more preferably 0.05 or more, and still more preferably 0.1 or more.
On the other hand, by setting the content of the Y component to 0.3 or less in chemical composition ratio, the crystal structure can be maintained in a rhombohedral system while retaining the elements that contribute to charge and discharge, and it can function as an active material. can be done. Therefore, the content of component Y is preferably 0.3 or less, more preferably 0.25 or less, and still more preferably 0.2 or less in terms of chemical composition ratio.

The Sc component has a rhombohedral crystal structure when the chemical composition ratio is greater than 0 when the chemical composition is Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ It is an optional ingredient that can be stabilized. Therefore, the Sc content is preferably greater than 0, more preferably 0.02 or more, still more preferably 0.05 or more, and still more preferably 0.1 or more.
On the other hand, by setting the content of the Sc component to 0.3 or less in chemical composition ratio, the crystal structure can be maintained in a rhombohedral system while retaining the elements that contribute to charge and discharge, and it can function as an active material. can be done. Therefore, the content of the Sc component is preferably 0.3 or less, more preferably 0.25 or less, still more preferably 0.2 or less in terms of chemical composition ratio.

When the Mn component contains more than 0 in the chemical composition ratio when the chemical composition is Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ , the value of Fe or Ti increases by charging and discharging. It is an optional component that can adjust the expansion and contraction when the number changes and stabilize the crystal structure. Therefore, the Mn content is preferably greater than 0, more preferably 0.02 or more, still more preferably 0.05 or more, and still more preferably 0.1 or more.
On the other hand, by setting the content of the Mn component to 0.3 or less in chemical composition ratio, the charge/discharge potential can be maintained at a low potential. Therefore, the content of the Mn component is preferably 0.3 or less, more preferably 0.25 or less, still more preferably 0.2 or less in chemical composition ratio.

When the Ni component contains more than 0 in the chemical composition ratio when the chemical composition is Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ , the value of Fe or Ti is reduced by charging and discharging. It is an optional component that can adjust the expansion and contraction when the number changes and stabilize the crystal structure. Therefore, the Ni content is preferably more than 0, more preferably 0.02 or more, still more preferably 0.05 or more, and still more preferably 0.1 or more.
On the other hand, by setting the content of the Ni component to 0.3 or less in chemical composition ratio, the charge/discharge potential can be maintained at a low potential. Therefore, the content of the Ni component is preferably 0.3 or less, more preferably 0.25 or less, still more preferably 0.2 or less in chemical composition ratio.

When the Cr component contains more than 0 in the chemical composition ratio when the chemical composition is Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ , the value of Fe or Ti increases by charging and discharging. It is an optional component that can adjust the expansion and contraction when the number changes and stabilize the crystal structure. Therefore, the Cr content is preferably greater than 0, more preferably 0.02 or more, still more preferably 0.05 or more, and still more preferably 0.1 or more.
On the other hand, by setting the content of the Cr component to 0.3 or less in chemical composition ratio, the charge/discharge potential can be maintained at a low potential. Therefore, the content of the Cr component is preferably 0.3 or less, more preferably 0.25 or less, still more preferably 0.2 or less in chemical composition ratio.

When the chemical composition of the V component is Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ and the chemical composition ratio is greater than 0, the value of Fe or Ti increases by charging and discharging. It is an optional component that can adjust the expansion and contraction when the number changes and stabilize the crystal structure. Therefore, the V content is preferably greater than 0, more preferably 0.02 or more, still more preferably 0.05 or more, and still more preferably 0.1 or more.
On the other hand, by setting the content of the V component to 0.3 or less in chemical composition ratio, the charge/discharge potential can be maintained at a low potential. Therefore, the content of component V is preferably 0.3 or less, more preferably 0.25 or less, and still more preferably 0.2 or less in terms of chemical composition ratio.

When the Co component contains more than 0 in the chemical composition ratio when the chemical composition is Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ , the value of Fe or Ti decreases due to charging and discharging. It is an optional component that can adjust the expansion and contraction when the number changes and stabilize the crystal structure. Therefore, the Co content is preferably greater than 0, more preferably 0.02 or more, still more preferably 0.05 or more, and still more preferably 0.1 or more.
On the other hand, by setting the Co component content to 0.3 or less in chemical composition ratio, the charge/discharge potential can be maintained at a low potential. Therefore, the content of the Co component is preferably 0.3 or less, more preferably 0.25 or less, and still more preferably 0.2 or less in terms of chemical composition ratio.

When the chemical composition of the Mg component is Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ and the chemical composition ratio exceeds 0, Li is increased due to the balance of valences. It is an optional component that can lower the potential by being contained in the crystal. Therefore, the Mg content is preferably more than 0.01, more preferably 0.03 or more, and still more preferably 0.05 or more.
On the other hand, by setting the content of the Mg component to 0.2 or less in chemical composition ratio, the Mg component dissolves into the lithium ion conductive glass electrolyte due to the stabilization of the crystal structure and the reaction with the lithium ion conductive glass electrolyte. By generating a covalent alkali effect, it is possible to suppress lowering of the conductivity of the lithium ion conductive glass. Therefore, the content of the Mg component is preferably 0.3 or less, more preferably 0.2 or less, still more preferably 0.15 or less in terms of chemical composition ratio.

When the Ca component contains more than 0 in the chemical composition ratio when the chemical composition is Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ , Li is increased due to the balance of valences. It is an optional component that can lower the potential by being contained in the crystal. Therefore, the Ca content is preferably more than 0.01, more preferably 0.03 or more, and still more preferably 0.05 or more.
On the other hand, by setting the content of the Ca component to 0.2 or less in chemical composition ratio, the Ca component dissolves into the lithium ion conductive glass electrolyte due to the stabilization of the crystal structure and the reaction with the lithium ion conductive glass electrolyte. By generating a covalent alkali effect, it is possible to suppress lowering of the conductivity of the lithium ion conductive glass. Therefore, the content of the Ca component is preferably 0.3 or less, more preferably 0.2 or less, and still more preferably 0.15 or less in terms of chemical composition ratio.

When the Ti component has a chemical composition of Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ and the chemical composition ratio exceeds 0.1, the valence of Ti changes. It is an optional component that can increase the charge/discharge capacity. Therefore, the Ti content is preferably more than 0.1, more preferably 0.2 or more, still more preferably 0.3 or more, and still more preferably 0.4 or more.
On the other hand, by setting the content of the Ti component to 1.95 or less in terms of chemical composition ratio, the crystal structure can be maintained in the rhombohedral system and can function as an active material. Therefore, the content of the Ti component is preferably 1.95 or less, more preferably 1.9 or less, still more preferably 1.8 or less in chemical composition ratio.

When the Zr component contains more than 0.1 in chemical composition ratio when the chemical composition is Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ , the valence of T changes. It is an optional component capable of stabilizing the crystal structure and improving the cycle characteristics because it does not change its valence even when it is subjected to sintering. The Zr content is preferably greater than 0.1, more preferably 0.2 or more, and still more preferably 0.3 or more.
On the other hand, by setting the content of the Zr component to 1.9 or less in chemical composition ratio, the lithium ion conductivity of the crystal itself can be maintained at a high level, and the reaction resistance can be lowered. Therefore, the content of the Ti component is preferably 1.9 or less, more preferably 1.8 or less, still more preferably 1.7 or less in terms of chemical composition ratio.

When the Ge component contains more than 0.1 in chemical composition ratio when the chemical composition is Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ , the valence of T changes. It is an optional component capable of stabilizing the crystal structure and improving the cycle characteristics because it does not change its valence even when it is subjected to sintering. The Ge content is preferably greater than 0.1, more preferably 0.2 or more, and still more preferably 0.3 or more.
On the other hand, by setting the content of the Ge component to 1.9 or less in chemical composition ratio, the lithium ion conductivity of the crystal itself can be maintained at a high level, and the reaction resistance can be lowered. Therefore, the content of the Ge component is preferably 1.9 or less, more preferably 1.8 or less, still more preferably 1.7 or less in terms of chemical composition ratio.

When the Sn component contains more than 0.1 in chemical composition ratio when the chemical composition is Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ , the valence of T changes. It is an optional component capable of stabilizing the crystal structure and improving the cycle characteristics because it does not change its valence even when it is subjected to sintering. The Sn content is preferably more than 0.1, more preferably 0.2 or more, and still more preferably 0.3 or more.
On the other hand, by setting the content of the Sn component to 1.9 or less in chemical composition ratio, the lithium ion conductivity of the crystal itself can be maintained at a high level, and the reaction resistance can be lowered. Therefore, the content of the Sn component is preferably 1.9 or less, more preferably 1.8 or less, still more preferably 1.7 or less in terms of chemical composition ratio.

When the P component has a chemical composition of Li _1+x+y+2Z A _Z M _x T _2-x-z P _3-y Si _y O ₁₂ and is substituted with Si or the like, the chemical composition ratio exceeds 2.5. , is an essential component that can maintain the rhombohedral crystal system. Therefore, the P content is preferably more than 2.5, more preferably 2.6 or more, more preferably 2.7 or more, still more preferably 2.8 or more, still more preferably 2.85 or more. In order to stabilize the crystal structure, 3 may be left as it is without substituting Si or the like.
On the other hand, by setting the content of the P component to 3 or less in chemical composition ratio, Si can be included, but the potential can be lowered by including a large amount of Li in the crystal due to the valence balance. Therefore, the content of the P component is preferably 3 or less, more preferably 2.95 or less, still more preferably 2.9 or less in terms of chemical composition ratio.

When the Si component has a chemical composition of Li _1+x+y+2Z A _Z M _x T _2-x-y P _3-y Si _y O ₁₂ and contains more than 0.01 in chemical composition ratio, Li is an optional component that can lower the potential by including a large amount of in the crystal. Therefore, the Si content is preferably more than 0.01, more preferably 0.02 or more, and still more preferably 0.05 or more.
On the other hand, by setting the content of the Si component to 0.5 or less in chemical composition ratio, the crystal structure can be stabilized and the firing temperature can be lowered. Therefore, the content of the Si component is preferably 0.5 or less, more preferably 0.3 or less, still more preferably 0.2 or less in terms of chemical composition ratio.

The composition of the negative electrode material according to the present invention can be confirmed by ICP emission spectroscopic analysis for the Li component. Other compositions can be confirmed by fluorescent X-ray analysis measurement. Moreover, when dispersed in an electrode, it can be analyzed by EDX measurement of a transmission electron microscope. In this case, the Li component may be estimated from the balance of the valences of the other compositions, since there is an analytical difference and the amount of Li is unknown due to the negative electrode active material.

When the content of the glass 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. The glass electrolyte is a component that increases the density of the positive electrode layer and increases the energy density per volume. Therefore, the content of the glass 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.
On the other hand, by setting the content of the glass electrolyte to 20% by mass or less with respect to the total mass of the positive electrode layer material, the glass electrolyte having a lower lithium ion conductivity than the ceramic electrolyte is excessively present. A decrease in ionic conductivity can be suppressed. In addition, since electron conduction in the negative electrode layer is caused by electron transfer caused by contact or bonding between conductive aids, resistance to electronic conduction increases when contact between conductive aids is inhibited by a glass electrolyte that does not have electronic conductivity. get higher Therefore, it is possible to suppress the decrease in electronic conductivity caused by the excessive presence of the glass electrolyte having no electronic conductivity. Therefore, the content of the glass electrolyte is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

Although the ceramic electrolyte or glass ceramic electrolyte of the negative electrode layer material of the present invention is not particularly limited, it is preferably a lithium-containing phosphate compound having a rhombohedral crystal system. Its chemical formula is represented by Li _x M' ₂ P ₃ O ₁₂ (X=1 to 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. . Also, part of P may be replaced with Si or B, and part of O may be replaced with F, Cl, or the like. _{For example , Li1.15Ti1.85Al0.15Si0.05P2.95O12 , Li1.2Ti1.8Al0.1Ge0.1Si0.05P2.95O _ _ _ _ _ _ 12} or the like can be used. Also, materials with different compositions may be mixed or combined. The surface may be coated with a glass electrolyte or the like. Alternatively, glass-ceramics that deposit a crystal phase of a lithium-containing phosphate compound having a NASICON-type structure by heat treatment may be used. Here, the mixing ratio of Li ₂ O in the glass-ceramics is preferably 8% by mass or less in terms of oxide. Li, La, Mg, Ca, Fe, Co, Cr, Mn, Ti, Zr, Sn, Y, Sc, P, Si, O, In, Nb, F, LISICON type, PE Using a solid electrolyte that has a loovskite type, β-Fe ₂ (SO ₄ ) ₃ type, and Li ₃ In ₂ (PO ₄ ) ₃ type crystal structure and conducts Li ions at room temperature at 1×10 ⁻⁵ S/cm or more Also good. Also, the above electrolyte may be mixed.

Materials having electron conductivity, such as carbon, graphite, carbon nanotubes, aluminum alloys, zinc alloys, silver, and ruthenium, can be used as the conductive aid for the negative electrode layer material of the present invention. Different materials may be mixed or combined.
The content of the conductive aid 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 aid.
In particular, when the content is 5% by mass or more, the electron conduction network formed by the conductive aid is easily secured, so that the charge/discharge characteristics and battery capacity of the battery can be easily improved. Therefore, the total content of the conductive aid in the negative electrode layer is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 8% by mass or more.
On the other hand, by setting the content to 30% by mass or less, the content of the negative electrode material contained in the negative electrode layer increases, so that the energy density of the all-solid-state battery can be increased. Therefore, the content of the conductive aid in the negative electrode layer is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

(positive electrode layer)
The positive electrode layer in the all-solid-state battery of the present invention is obtained by sintering a material containing a positive electrode material, at least one of a glass electrolyte, a ceramics electrolyte, or a glass ceramics electrolyte as a lithium ion conductive solid electrolyte, and a conductive aid. is preferably
The type of positive electrode material for the positive electrode layer is not limited. The positive electrode material of the present invention is LiRPO ₄ having an olivine structure, where R is one or more of Fe, Co, Mn and Ni, and a portion thereof may be substituted with Al or the like. Also, part of P may be replaced with Si or B. Part of O may be replaced with F. Further, LiMn ₂ O ₄ having a spinel structure, layered oxide LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiNi _1/2 Mn _1/2 O ₂ , LiNiO ₂ , LiCoO ₂ etc. good too. The most suitable positive electrode material has an olivine structure in which oxygen is strongly bonded to phosphorus, since discharge capacity decreases when oxygen is released by reacting with the solid electrolyte during firing. The next preferred cathode material is LiMn ₂ O ₄ with a spinel structure, followed by the above layered oxides.
The content of the positive electrode 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 making this content 10% by mass or more, the battery capacity of the all-solid-state battery can be increased. Therefore, the content of the positive electrode material is preferably 10% by mass or more, more preferably 18% by mass or more. On the other hand, by setting the content to 60% by mass or less, the ion conductivity of the electrode layer can be easily ensured. Therefore, the content of the positive electrode 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 glass 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 glass electrolyte is a component that increases the density of the positive electrode layer and increases the energy density per volume. Therefore, the content of the glass 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.
On the other hand, by setting the content of the glass electrolyte to 20% by mass or less with respect to the total mass of the positive electrode layer material, the glass electrolyte having a lower lithium ion conductivity than the ceramic electrolyte is excessively present. A decrease in ionic conductivity can be suppressed. In addition, since electron conduction in the negative electrode layer is caused by electron transfer caused by contact or bonding between conductive aids, resistance to electronic conduction increases when contact between conductive aids is inhibited by a glass electrolyte that does not have electronic conductivity. get higher Therefore, it is possible to suppress the decrease in electronic conductivity caused by the excessive presence of the glass electrolyte having no electronic conductivity. Therefore, the content of the glass electrolyte is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 10% by mass or less.

Although the ceramic electrolyte or glass ceramic electrolyte of the positive electrode layer material of the present invention is not particularly limited, it is preferably a lithium-containing phosphate compound having a rhombohedral crystal system. Its chemical formula is Li _x M″ ₂ P ₃ O ₁₂ (X=1-1.7), where M″ is Zr, Ti, Fe, Mn, Co, Cr, Ca, Mg, Sr, One or more elements selected from the group consisting of Y, Sc, Sn, La, Ge, Nb and Al. Also, part of P may be replaced with Si or B, and part of O may be replaced with F, Cl, or the like. _{For example , Li1.15Ti1.85Al0.15Si0.05P2.95O12 , Li1.2Ti1.8Al0.1Ge0.1Si0.05P2.95O _ _ _ _ _ _ 12} or the like can be used. Also, materials with different compositions may be mixed or combined. The surface may be coated with a glass electrolyte or the like. Alternatively, glass-ceramics that deposit a crystal phase of a lithium-containing phosphate compound having a NASICON-type structure by heat treatment may be used. Here, the mixing ratio of Li ₂ O in the glass ceramics is preferably 8% by mass or less in terms of oxide. Li, La, Mg, Ca, Fe, Co, Cr, Mn, Ti, Zr, Sn, Y, Sc, P, Si, O, In, Nb, F, LISICON type, PE Using a solid electrolyte having a loovskite type, β-Fe ₂ (SO ₄ ) ₃ type, Li ₃ In ₂ (PO ₄ ) ₃ type crystal structure and conducting Li ions at room temperature at 1×10 ⁻⁵ S/cm or more Also good. Also, the above electrolyte may be mixed.

The content of the lithium conductive solid electrolyte is preferably 30% by mass to 80% by mass with respect to the total mass of the positive electrode layer material.
In particular, by setting the content to 30% by mass or more, it becomes easier to secure a movement path for lithium ions formed by the glass electrolyte, so that the charging/discharging characteristics and battery capacity of the battery can be more easily improved. Therefore, the total content of the lithium conductive solid electrolyte in the electrode layer is preferably 30% by mass or more, more preferably 45% by mass or more, and even more preferably 55% by mass or more.
On the other hand, by setting the content to 80% by mass or less, the content of the positive electrode material contained in the positive electrode layer increases, so that the energy density of the all-solid-state battery can be increased. Therefore, the content of the lithium conductive solid electrolyte in the positive electrode layer is preferably 75% by mass or less, more preferably 70% by mass or less, and even more preferably 65% by mass or less.
Materials having electron conductivity, such as carbon, graphite, carbon nanotubes, aluminum alloys, zinc alloys, silver, and ruthenium, can be used as the conductive aid for the positive electrode layer material of the present invention. Different materials may be mixed or combined.
The content of the conductive aid with respect to the total weight of the positive electrode layer material is preferably 5% by mass to 30% by mass, although it depends on the type of the conductive aid.
In particular, when the content is 5% by mass or more, the electron conduction network formed by the conductive aid is easily secured, so that the charge/discharge characteristics and battery capacity of the battery can be easily improved. Therefore, the total content of the conductive aid in the positive electrode layer is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 8% by mass or more.
On the other hand, by setting the content to 30% by mass or less, the content of the positive electrode material contained in the positive electrode layer increases, so that the energy density of the all-solid-state battery can be increased. Therefore, the content of the conductive aid in the positive electrode layer is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

(Solid electrolyte layer)
The solid electrolyte layer in the all-solid-state battery of the present invention is preferably a sintered material containing at least one of a glass electrolyte, a ceramics electrolyte, and a glass-ceramics electrolyte as a solid electrolyte.

When the content of the glass electrolyte with respect to the total mass of the solid electrolyte layer material is 3% by mass or more, the glass electrolyte spreads over the ceramic electrolyte interface, and the ion conductivity of the solid electrolyte layer can be increased. Moreover, since the density of the solid electrolyte layer can be increased, the strength 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 glass 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 5% by mass or more.
On the other hand, when the content of the glass electrolyte exceeds 15% by mass, the film thickness of the glass electrolyte connecting the ceramic electrolytes becomes thicker, and the distance through which lithium ions pass through the glass electrolyte becomes longer. The influence of the conductivity of the glass electrolyte, which is lower than that of the ceramics electrolyte, becomes stronger, and as a result, the ionic conductivity decreases. Therefore, by setting the content of the glass electrolyte to 15% by mass or less, it is possible to prevent the decrease in ion conductivity as described above. Therefore, the content of the glass electrolyte is preferably 15% by mass or less, more preferably 12% by mass or less, and even more preferably 9% by mass or less.

The type of ceramic electrolyte contained in the solid electrolyte layer material is not limited. The solid electrolyte of the present invention is a lithium-containing phosphate compound having a rhombohedral NASICON structure and is represented by the chemical formula Li _x L ₂ P ₃ O ₁₂ (X=1 to 1.7). 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. Also, part of P may be replaced with Si or B, and part of O may be replaced with F, Cl, or the like. _{For example , Li1.2Zr1.85Al0.15Si0.05P2.95O12 , Li1.2Zr1.85Al0.1Ti0.05Si0.05 , etc. can be} used _. can. Also, materials with different compositions may be mixed or combined. The surface may be coated with a glass electrolyte or the like. Lithium ion conductors different from the NASICON type, β-Fe ₂ (SO ₄ ) ₃ type Li ₃ In ₂ (PO ₄ ) ₃ , perovskite type lithium ion conductor La _0.51 Li _0.34 TiO _2.94 . You can use it.

It is preferable that the content of the lithium ion conductive solid electrolyte is 80% by mass or more with respect to the total mass of the solid electrolyte layer material. This facilitates the formation of paths for lithium ion conduction in the solid electrolyte layer, so that the lithium ion conductivity of the solid electrolyte layer can be further enhanced.
On the other hand, the upper limit of the content of the lithium ion conductive solid electrolyte is not particularly limited, and may be 100% by mass.

Example <Preparation of negative electrode material>
The negative electrode material was produced by three procedures of preparation, firing, and pulverization.

(mixing)
LiPO ₃ , Fe ₂ O ₃ , MgO, Al(PO ₃ ) ₃ , Y ₂ O ₃ , MnO ₂ , CoO, TiO ₂ , GeO ₂ , ZrO ₂ , orthophosphoric acid (H ₃ PO ₄ ), and SiO ₂ were mixed in a stoichiometric ratio. Components other than orthophosphoric acid were mixed in an alumina mortar, then orthophosphoric acid was added, kneaded for 5 minutes with a foam removing Rentaro, and then cooled for 2 minutes.

(firing)
Examples 1 to 11 and 16, which do not use Zr, were placed in a quartz crucible and fired in the air at 1000° C. for 5 hours. Examples 12 and 13 using 0.2 and 0.5 stoichiometric ratios of Zr were calcined in air at 1100° C. for 5 hours. Examples 14 and 15 using 1 and 1.5 stoichiometric ratios of Zr were fired at 1100°C for 5 hours, pulverized in an alumina mortar, transferred onto a platinum plate, and fired at 1350°C for 1 hour.

(crushing)
The fired sample was pulverized to 106 μm mesh pass using an alumina mortar and pestle, and then pulverized to 1.5 μm or less at D90 with a wet planetary ball mill.

(Powder X-ray diffraction measurement)
The obtained sample was ground to 106 mesh pass and subjected to powder X-ray diffraction measurement to evaluate the crystal structure. The results of X-ray diffraction measurement of Example 4 are shown in FIG. 1, and the results of X-ray diffraction measurement of Example 15 are shown in FIG. All of them had a rhombohedral crystal system like NASICON type LATP12 or LAZP12. It was confirmed that all negative electrode materials of Examples 1 to 17 were rhombohedral crystal systems.
(ICP emission spectroscopic analysis)
The Li component of the fired sample was evaluated by XRF-ZSX Primus II (manufactured by Agilent Technologies). All samples were confirmed to be within ±10% of the charged composition.
(Fluorescent X-ray analysis)
Elements other than the Li component in the fired sample were evaluated by XRF/ZSX Primus II (manufactured by RIGAKU). It was confirmed that all compositions were within ±10% of the starting composition.

<Preparation of solid electrolyte>
<Preparation of solid electrolyte LATP12>
_{Li1.2Al0.15Ti1.85Si0.05P2.95O12 was prepared as} one of the _{ceramic electrolytes} . Fine powders of LiPO ₃ , TiO ₂ , Al(PO ₃ ) ₃ and SiO ₂ as raw materials were mixed with H ₃ PO ₄ solution in a stoichiometric ratio, and then fired in a quartz crucible at 1000° C. for 5 hours. The fired raw material mixture 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).

<Preparation of solid electrolyte LAZP12>
As one of the solid _{electrolytes , Li1.2Al0.15Zr1.85Si0.05P2.95O12 containing} no _{Ti component} was prepared. Fine powders of LiPO ₃ , ZrO ₂ , Al(PO ₃ ) ₃ and SiO ₂ as raw materials were mixed with H ₃ PO ₄ solution in a stoichiometric ratio, and then fired on a platinum plate at 1400° C. for 1 hour. . The fired raw material mixture 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).

<Preparation of glass electrolyte>
Li ₂ O—Al ₂ O ₃ —P ₂ O ₅ system glass was produced as a glass electrolyte. After weighing and uniformly mixing the raw materials to contain ₂₀ wt% Li2O _{, 4.5} wt% _Al2O3 and 75.5 wt% _P2O5 in the oxide standard composition , was placed in a crucible and melted at 1250°C. A glass electrolyte was prepared by casting a molten glass in water. The above electrolyte was pulverized to a 106 μm mesh pass using a stamp mill and then pulverized to an average particle size of 1 μm or less with a wet planetary ball mill to obtain a glass electrolyte (hereinafter referred to as LIGAl9).

<Characteristic evaluation by liquid-based half-cell>
The prepared negative electrode material, acetylene black (Denka black: granular product manufactured by Denki Kagaku Kogyo Co., Ltd.) as a conductivity-imparting material, and PVdF (polyvinylidene fluoride) as a binder were mixed at a solid content mass ratio of 62:9. The mixture was mixed and kneaded so as to have a thickness of 9, sheet-formed on a copper foil with a thickness gap of 0.2 mm, punched out into a diameter of 1.5 cm, and a density of 2.0 cm without the copper foil by a mighty press. It was pressed to 5 g/cm ³ to obtain an electrode mixture.

After that, an HS cell (manufactured by Hosen Co., Ltd.) was charged with metallic lithium, a separator (manufactured by Polypore Celgard 2401), and the prepared electrode mixture as an electrolyte, respectively, and 1 M LiPF ₆ was dissolved in ethyl methyl carbonate / ethylene carbonate 7 / 3 mixed electrolyte solution (manufactured by Toyama Pharmaceutical Co., Ltd.) was filled and sealed to produce a coin-type lithium secondary battery. A series of battery assembly including the positive and negative electrodes, diaphragm, electrolyte solution, etc. was performed in an argon-substituted glove box.

The HS cell incorporating the negative electrode material obtained as described above was charged and discharged at a constant current at a discharge rate of 1/10 C at 25° C. in an operating voltage range of 2.0V to 3.2V. FIG. 3 shows the charging/discharging measurement results when the negative electrode material of Example 4 was used. Table 2 shows the evaluation results of the liquid-based half-cells in which the negative electrode materials of Examples 1 to 17 were used. A discharge capacity could be confirmed for any of the negative electrode materials.

<Characteristic evaluation by all-solid-state half-cell>
In order to confirm the function of the negative electrode material in an all-solid-state battery, a half-cell was fabricated using Li metal as a counter electrode, and the charge-discharge characteristics of the negative electrode material in the all-solid-state battery were evaluated. The half-cell is composed of a Li metal, a Li ion-conducting polymer electrolyte layer, a solid electrolyte layer and a negative electrode layer. The Li-ion conductive polymer electrolyte is ZEOSPAN8100 (trademark) (Nippon Zeon) and Li-TFSI (chemical formula (CF ₃ SO ₂ ) ₂ NLi) with a weight ratio of ZEOSPAN:Li-TFSI = 7.7:2.3. The mixture was mixed in the manner described above, made into a slurry with ethanol, formed into a sheet, and then dried.
The solid electrolyte layer and the negative electrode layer were produced by compacting powder, pressing, and then sintering.

Table 3 shows the composition of the negative electrode layer, and Table 4 shows the composition of the solid electrolyte layer.
The negative electrode layer and the solid electrolyte layer were prepared according to Tables 3 and 4, 100 g of Φ5 mm YTZ balls (manufactured by Nikkato) were added, and mixed and After three 3-minute cooling cycles, the YTZ balls were separated and the solvent was dried off. The dried powder was pulverized with a laboratory miller and used in subsequent experiments.
After adding 30 mg of the mixed negative electrode layer material to a mold of 11 mm in diameter and smoothing the surface with a spatula and smoothing the surface with a pressing tool, 60 mg of the mixed solid electrolyte layer material was added and the surface was smoothed with a spatula. Then, after being pressed at a pressure of 2000 kg/cm ² , it was fired at 600° C. to obtain a sintered body. After lightly polishing the surface of the negative electrode layer and the surface of the solid electrolyte layer with No. 800 water-resistant abrasive paper, a copper foil for current collection was adhered to the negative electrode layer side using carbon paste and carbon paper, and placed in a dry room with a dew point of -50°C. calcined at 150° C. for 1 hour.
After the Li metal was press-bonded to the copper foil, the Li ion-conducting polymer electrolyte was used as a protective layer and adhered so that the Li ion-conducting polymer electrolyte and the solid electrolyte layer of the sintered body were in contact with each other. The Li metal, the sintered body, and the lithium ion conductive polymer electrolyte were vacuum-packed in an aluminum laminate package with the copper foil exposed so that it could be connected to an external terminal.
Table 5 shows the density and resistance measurement results of the all-solid-state half-cells of Comparative Example 1, Comparative Example 2, Example 18 and Example 19. The mass was evaluated using an electronic balance capable of measuring up to 0.1 mg, the thickness was evaluated using a digital micrometer, and the diameter was evaluated using a digital caliper. For resistance measurement, an LCR meter (3522-50 LCR HiTESTER manufactured by Hioki Denki Co., Ltd.) was used to measure resistance at 1 V and 1 kHz. Comparative Example 2 and Example 19 using LATP12, which is a Ti-based solid electrolyte, as an electrolyte layer are compared to Comparative Example 1 and Example 18, which uses LAZP12, which is a reduction-resistant solid electrolyte that does not use Ti, as an electrolyte layer. The resistance was as low as about 1/20. It was confirmed that the resistance value of the all-solid-state half-cell can be greatly reduced by using Ti-based LATP12 as the solid electrolyte.
4 shows comparative example 1, FIG. 5 shows comparative example 2, FIG. 6 shows example 18, and FIG. The charging/discharging test was evaluated using an Aska Electronics charging/discharging tester (ACD-M01A). The charge/discharge current was 17 μA, with a 1.2 V cutoff for Comparative Example 1, a 2.0 V cutoff for Comparative Example 2 and Example 18, and a 2.4V CC charge for Example 19 followed by CC discharge with a 3V cutoff. evaluated.
Comparative Example 1 showed a discharge voltage of 2.0V. In Comparative Example 2, although the resistance was low, the irreversible capacity between charge and discharge was high, and the discharge voltage was about 2.7 V in spite of using TiO ₂ as the negative electrode material. As a result, this test also confirmed that LATP12, which is a solid electrolyte, cannot use TiO ₂ as a negative electrode active material. In Comparative Example 2 using LAZP12 which does not use Ti, which is a reduction-resistant solid electrolyte, it was confirmed that TiO ₂ can be charged and discharged. Similarly, in Example 18, it was confirmed that the use of the reduction-resistant solid electrolyte LAZP12 enabled charging and discharging. Example 19 using LATP12, which is a Ti-based solid electrolyte, showed an average discharge voltage of 2.6V. It was confirmed that the negative electrode material Li _1.5 Fe _0.5 Ti _1.5 P ₃ O ₁₂ prepared in Example 19 could be charged and discharged using a LATP12 solid electrolyte. The results of Examples 19 to 35, in which charge-discharge characteristics of the half-cells composed of the negative electrode active materials of Examples 1 to 17 were evaluated using LATP12 solid electrolyte by the same experimental method as in Example 19, are shown in Table 6. show.

<Evaluation with all-solid-state battery>
An all-solid battery was fabricated using LiMn _0.75 Fe _0.25 PO ₄ as a positive electrode material, and the characteristics of the negative electrode material were evaluated.

(positive electrode layer)
The composition of the positive electrode layer was prepared according to Table 7, 100 g of Φ5 mm YTZ balls (manufactured by Nikkato) were added, and using Awatori Rentaro (ARV-200 manufactured by Thinky), mixing was performed for 5 minutes at 1000 rpm and cooling for 3 minutes was repeated three times. After that, the YTZ balls were separated and the solvent was removed by drying. The dried powder was pulverized with a laboratory miller and used in subsequent experiments.

(All-solid-state battery configuration)
In order to confirm the function of the prepared negative electrode material as an electrode material, an all-solid-state battery was constructed with the composition shown in Table 8. After adding 30 mg of the mixed negative electrode layer material to a mold of 11 mm in diameter and smoothing the surface with a spatula and smoothing the surface with a pressing tool, 60 mg of the mixed solid electrolyte layer material was added and the surface was smoothed with a spatula. Finally, 30 mg of the mixed positive electrode layer material was added and the surface was smoothed with a spatula. Then, after being pressed at a pressure of 2000 kg/cm ² , it was fired at 600° C. to obtain a sintered body. The surface of the negative electrode layer and the surface of the positive electrode were lightly polished with No. 800 water-resistant abrasive paper, and the outer periphery was ground by about 100 μm to suppress short circuits on the outer periphery. and an aluminum foil for current collection was adhered to the positive electrode layer side using carbon paste and carbon paper. It was calcined at 150°C for 1 hour in a dry room with a dew point of -50°C. After baking, the all-solid-state battery was shielded from the outside air by vacuum-packing with an aluminum laminate film so that the current-collecting copper foil and aluminum foil were exposed to the outside.
The mass was evaluated using an electronic balance capable of measuring up to 0.1 mg, the thickness was evaluated using a digital micrometer, and the diameter was evaluated using a digital caliper. For resistance measurement, an LCR meter (3522-50 LCR HiTESTER manufactured by Hioki Denki Co., Ltd.) was used to measure resistance at 1 V and 1 kHz. The charging/discharging test was evaluated using an Aska Electronics charging/discharging tester (ACD-M01A). The charging/discharging current was 17 μA, Comparative Example 3 was CC charged with a 3.2V cutoff, Comparative Example 4 and Example 36 were CC charged with a 2.2V cutoff and then CC discharged with a 0.1V cutoff.
Table 9 shows the density and resistance measurement results of the prototype all-solid-state battery. FIG. 8 shows the results of charge/discharge measurement of Example 36. In FIG. In Comparative Example 3, the discharge voltage can be increased, but the resistance is high. Comparative Example 4 had a low resistance, similar to the result of the half cell of Comparative Example 2, but did not exhibit charging/discharging behavior after the second cycle. It was confirmed that the resistance of Example 36 using LATP12 as a solid electrolyte was 1/40 of that of Comparative Example 3 using LAZP12 solid electrolyte. As a result, it was confirmed that LiMn _0.75 Fe _0.25 PO ₄ can function as a negative electrode for all-solid-state batteries.

Claims (3)

Li _1+x+y+2Z A _Z M _x Ti _2-x-z P _3-y Si _y O ₁₂ (x=0.1-0.8, y=0-0.5, z=0-0.2), A negative electrode active material having a rhombohedral crystal structure before charging.
(A is at least one selected from Mg and Ca.)
(M is one or more selected from Fe, Mn, Co, Ni, Cr, and V.) An all-solid battery using the negative electrode active material according to claim 1 . An all-solid battery using the negative electrode active material according to claim 1 and using at least one of a glass electrolyte, a ceramics electrolyte, and a glass ceramics electrolyte for at least one of a positive electrode layer, a negative electrode layer, and an electrolyte layer.

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