JP2012104280A - Sintered body for battery, all-solid lithium battery, and method for manufacturing sintered body for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sintered body for a battery offering excellent charge-discharge characteristics even if a heterogeneous phase occurs.SOLUTION: The sintered body for a battery contains a solid electrolyte material represented by the formula LiAlGe(PO)(0≤x≤2), and an active material containing Li, Ti, and O. When the sintered body is analyzed by X-ray diffraction, an ingredient other than the solid electrolyte material or the active material is detected at the interface between the solid electrolyte material and the active material.

Description

  The present invention relates to a sintered body for a battery used in, for example, an all-solid lithium secondary battery.

  With the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones in recent years, development of batteries that are used as power sources has been regarded as important. Also in the automobile industry and the like, development of high-power and high-capacity batteries for electric vehicles or hybrid vehicles is being promoted. Currently, among various batteries, lithium ion secondary batteries are attracting attention from the viewpoint of high energy density.

  Currently marketed lithium-ion secondary batteries use an electrolyte containing a flammable organic solvent, so it is safe to install safety devices that prevent temperature rise during short circuits and to prevent short circuits. Improvement is required. In contrast, an all-solid lithium secondary battery in which the electrolyte solution is changed to a solid electrolyte layer to make the battery all solid does not use a flammable organic solvent in the battery, so the safety device can be simplified and manufactured. It is considered to be excellent in cost and productivity.

  An all-solid lithium secondary battery is usually a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid formed between the positive electrode active material layer and the negative electrode active material layer An electrolyte layer. As a battery sintered body used for an all solid lithium secondary battery, for example, in Patent Document 1, for an all solid lithium secondary battery including an active material layer and a solid electrolyte layer sintered and joined to the active material layer A laminate for an all-solid-state lithium secondary battery in which a component other than a constituent component of the active material layer and a constituent component of the solid electrolyte layer is not detected when analyzed by an X-ray diffraction method. The body is disclosed.

In Patent Document 2, a plurality of valence changes are possible, and an all-solid secondary material having a single-layer active material layer composed of a single layer containing active material materials having different redox potentials corresponding to each valence change. A battery is disclosed. Furthermore, it is disclosed that Li _{1 + y} Al _y Ge _2-y (PO ₄ ) ₃ (0 ≦ y ≦ 1) is used as the solid electrolyte.

JP 2007-5279 A JP 2009-123389 A

  When a sintered body for a battery is produced, a heterogeneous phase is generated at the interface between the solid electrolyte material and the active material material along with the sintering, so that the movement of ions is hindered. For this reason, there exists a problem that the charging / discharging characteristic of the sintered compact for batteries falls greatly.

  This invention is made | formed in view of the said problem, and even if it is a case where a different phase arises, it aims at providing the sintered compact for batteries from which a favorable charging / discharging characteristic is acquired.

In order to solve the above problems, in the present invention, a solid electrolyte material represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), Li, Ti, and O When the active material is contained and analyzed by X-ray diffraction, components other than the solid electrolyte material and the active material are detected at the interface between the solid electrolyte material and the active material. A sintered body for a battery is provided.

According to the present invention, a solid electrolyte material represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), and an active material containing Li, Ti, and O By using in combination, a sintered body for a battery can be obtained in which good charge / discharge characteristics can be obtained even when a different phase occurs at the interface between the two.

In the above invention, the active material _is preferably a Li ₄ Ti _{5 O 12.}

  In the above invention, when the battery sintered body produced an evaluation battery having an active material layer containing the solid electrolyte material and the active material, and a Li metal layer, It is preferable that the battery is fired at a temperature at which an evaluation battery having a discharge capacity of 30% or more with respect to the theoretical discharge capacity can be obtained. This is because a different phase is formed to such an extent that good charge / discharge characteristics can be obtained.

  In the said invention, it is preferable that the said sintered compact for batteries is a thing formed by baking at the temperature within the range of 550 degreeC-650 degreeC. This is because a different phase is formed to such an extent that good charge / discharge characteristics can be obtained.

  In the said invention, it is preferable that the said sintered compact for batteries is an active material layer containing the said solid electrolyte material and the said active material material.

  In the said invention, it is preferable that the said battery sintered compact has a solid electrolyte layer containing the said solid electrolyte material, and an active material layer formed on the said solid electrolyte layer and containing the said active material material. .

  Moreover, in this invention, it has the sintered compact for batteries mentioned above, The all-solid-state lithium battery characterized by the above-mentioned is provided.

  According to this invention, it can be set as the all-solid-state lithium battery with favorable charging / discharging characteristics by using the sintered compact for batteries mentioned above.

In the present invention, a solid electrolyte material represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), and an active material containing Li, Ti, and O And an intermediate preparation step for preparing an intermediate containing the solid electrolyte material and components other than the active material at the interface between the solid electrolyte material and the active material when analyzed by an X-ray diffraction method. And a firing step of firing the intermediate at a detected temperature. A method for producing a sintered body for a battery is provided.

According to the present invention, a solid electrolyte material represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), and an active material containing Li, Ti, and O By using in combination, it is possible to obtain a sintered body for a battery that can exhibit good charge / discharge characteristics even when a different phase is generated at the interface between the two.

In the above invention, the active material _is preferably a Li ₄ Ti _{5 O 12.}

  In the above invention, when an evaluation battery having an active material layer containing the solid electrolyte material and the active material material and a Li metal layer is produced at the firing temperature in the firing step, The temperature is preferably such that an evaluation battery having a discharge capacity of 30% or more with respect to the theoretical discharge capacity can be obtained. This is because a different phase is formed to such an extent that good charge / discharge characteristics can be obtained.

  In the said invention, it is preferable that the calcination temperature in the said baking process exists in the range of 550 degreeC-650 degreeC. This is because a different phase is formed to such an extent that good charge / discharge characteristics can be obtained.

  In this invention, even if it is a case where a heterogeneous phase arises, there exists an effect that the sintered compact for batteries which can obtain favorable charging / discharging characteristics can be provided.

It is a schematic sectional drawing which shows an example of the sintered compact for batteries of this invention. It is a schematic sectional drawing which shows the other example of the sintered compact for batteries of this invention. It is a schematic sectional drawing which shows an example of the all-solid-state lithium battery of this invention. It is a schematic sectional drawing which shows an example of the manufacturing method of the sintered compact for batteries of this invention. It is a schematic sectional drawing which shows the other example of the manufacturing method of the sintered compact for batteries of this invention. It is a result of XRD with respect to the sample obtained in Examples 1-3 and Comparative Examples 1 and 2. FIG. 4 is a result of TG / DTA for the sample obtained in Comparative Example 2. It is a result of charging / discharging characteristic evaluation with respect to the battery for evaluation using the sample obtained in Example 3.

  Hereinafter, the battery sintered body, the all solid lithium battery, and the method for producing the battery sintered body of the present invention will be described in detail.

A. Battery Sintered Body The battery sintered body of the present invention includes a solid electrolyte material represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), Li, Ti, When an active material containing O is contained and analyzed by X-ray diffraction, components other than the solid electrolyte material and the active material are detected at the interface between the solid electrolyte material and the active material. It is characterized by that.

FIG. 1 is a schematic cross-sectional view showing an example of a sintered body for a battery according to the present invention. A sintered body 10 for a battery in FIG. 1 includes a solid electrolyte layer 11 containing Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ that is a solid electrolyte material 1, and Li that is an active material 2. ₄ is a laminate having an active material layer 12 containing ₄ Ti ₅ O ₁₂ . Components other than the solid electrolyte material 1 and the active material 2 are detected at the interface between the solid electrolyte material 1 (solid electrolyte layer 11) and the active material 2 (active material layer 12). That is, a heterogeneous phase 3 is formed at the interface between the two.

FIG. 2 is a schematic cross-sectional view showing another example of the battery sintered body of the present invention. The battery sintered body 10 in FIG. 2 includes Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ that is the solid electrolyte material 1 and Li ₄ Ti ₅ O ₁₂ that is the active material 2. It is the active material layer 12 to be contained. Components other than the solid electrolyte material 1 and the active material 2 are detected at the interface between the solid electrolyte material 1 and the active material 2. That is, a heterogeneous phase 3 is formed at the interface between the two.

According to the present invention, a solid electrolyte material represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), and an active material containing Li, Ti, and O By using in combination, a sintered body for a battery can be obtained in which good charge / discharge characteristics can be obtained even when a different phase occurs at the interface between the two. Conventionally, it has been known that when a heterogeneous phase is generated, the conduction of Li ions is hindered and the charge / discharge characteristics are greatly deteriorated. However, as described in the examples described later, it has been confirmed that the charge / discharge characteristics are not significantly reduced by the above combination.

  The sintered body for a battery according to the present invention is a sintered body obtained by firing the solid electrolyte material and the active material. In general, sintering refers to a phenomenon that solidifies and becomes dense when an aggregate of solid powders is heated. Further, the sintered body refers to an object in which solid powder particles adhere to each other and are hardened by heat treatment. Whether or not the sintering has progressed sufficiently is determined, for example, by sticking a cello tape (registered trademark) to the surface of the sintered body and whether or not the components of the sintered body are transferred when it is peeled off. Can do. When the components of the sintered body are transferred to the peeled cellotape (registered trademark), it can be determined that the sintering has not progressed sufficiently. Whether or not the sintering has sufficiently progressed can also be determined by whether or not the fired member has a density (filling rate, porosity) that cannot be achieved by the compacting treatment.

Furthermore, when the sintered body for a battery of the present invention is analyzed by an X-ray diffraction method, components other than the solid electrolyte material and the active material are detected at the interface between the solid electrolyte material and the active material. Is one of the characteristics. That is, one feature is that a different phase is detected at the interface between the two. Here, the heterogeneous phase refers to a product derived from a decomposition product of a solid electrolyte material, a decomposition product of an active material, a reaction product of the solid electrolyte material and the active material, and the like. Whether or not a heterogeneous phase has occurred can be determined, for example, by an X-ray diffraction measurement method using RINT Ultimate III manufactured by Rigaku.
Hereinafter, the battery sintered body of the present invention will be described for each configuration.

1. Solid electrolyte material in the solid electrolyte material present invention is represented by the general formula _{Li 1 + x Al x Ge 2} -x (PO 4) 3 (0 ≦ x ≦ 2). In the above general formula, the range of x may be 0 or more, preferably greater than 0, more preferably 0.1 or more, and even more preferably 0.3 or more. On the other hand, the range of x may be 2 or less, preferably 1.9 or less, more preferably 1 or less, and even more preferably 0.7 or less. In particular, the solid electrolyte material is _preferably Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ .

  The solid electrolyte material usually has a composition capable of forming a NASICON structure, and may be amorphous (glass), crystalline, or crystalline. There may be. Here, “amorphous” means a state in which a predetermined crystal peak is not detected by X-ray diffraction, and “having crystallinity” means a state in which a predetermined crystal peak is detected by X-ray diffraction. “Crystalline” means a state of being heat-treated at a temperature equal to or higher than the crystallization temperature. The state of the solid electrolyte material in the battery sintered body can be determined by, for example, an X-ray diffraction measurement method using RINT Ultimate III manufactured by Rigaku.

The shape of the solid electrolyte material before sintering is, for example, powdery, and the average particle diameter is preferably in the range of 0.001 μm to 100 μm, more preferably in the range of 0.01 μm to 10 μm. preferable. If the average particle size is too large, it may be difficult to obtain a dense sintered body for a battery. If the average particle size is too small, it may be difficult to produce a solid electrolyte material. Because. Incidentally, the average particle diameter can be defined by the D ₅₀ as measured by a particle size distribution meter. Moreover, it can define similarly about the average particle diameter of each material mentioned later.

2. Active material The active material in the present invention contains Li, Ti, and O. Examples of such an active material include Li ₄ Ti ₅ O ₁₂ , Li ₂ TiO ₃ , Li ₄ TiO ₄ , and Li ₂ Ti ₃ O ₇ , among which Li ₄ Ti ₅ O ₁₂ is preferable.

  The active material may be amorphous, but is usually crystalline or crystalline. The definition of amorphous or the like is the same as described above.

  The shape of the active material before sintering is, for example, powdery, and the average particle diameter is preferably in the range of 0.001 μm to 100 μm, more preferably in the range of 0.01 μm to 10 μm. preferable. If the average particle size is too large, it may be difficult to obtain a dense sintered body for a battery. If the average particle size is too small, it may be difficult to produce an active material. Because.

3. Battery Sintered Body As an example of the structure of the battery sintered body of the present invention, a laminated body having a solid electrolyte layer 11 and an active material layer 12 can be cited as shown in FIG. The solid electrolyte layer 11 and the active material layer 12 are usually integrated with each other by sintering. The content of the solid electrolyte material in the solid electrolyte layer of the laminate is not particularly limited as long as a predetermined effect is obtained, but it is more from the viewpoint of suppressing the occurrence of heterogeneous phases. Specifically, it is preferably 1% by volume or more, and more preferably 10% by volume or more. The solid electrolyte layer may be a layer made only of the solid electrolyte material. Although the thickness of the said solid electrolyte layer is not specifically limited, For example, it is preferable to exist in the range of 0.1 micrometer-1 mm, and it is more preferable to exist in the range of 1 micrometer-100 micrometers. The filling rate of the solid electrolyte layer varies depending on the type of the solid electrolyte material to be used. For example, it is preferably 70% by volume or more, and more preferably in the range of 80% by volume to 100% by volume. preferable.

  On the other hand, the content of the active material in the active material layer of the laminate is not particularly limited, but is preferably in the range of 40% by volume to 100% by volume, for example, 70% by volume to 100% by volume. % Is more preferable. Note that the active material layer may be a layer made of only the active material. Although the thickness of the said active material layer is not specifically limited, For example, it is preferable to exist in the range of 0.1 micrometer-1 mm, and it is more preferable to exist in the range of 1 micrometer-100 micrometers. The filling rate of the active material layer varies depending on the type of active material used, but is preferably 50% by volume or more, for example. The active material layer may further contain the above-described solid electrolyte material. Further, when the battery sintered body is a laminate, the laminate may have an active material layer on one surface of the solid electrolyte layer, and the active material on each side of the solid electrolyte layer. It may have a layer (positive electrode active material layer and negative electrode active material layer). In the latter case, the battery sintered body can be used as a power generation element of the battery as it is.

  As another example of the structure of the battery sintered body of the present invention, as shown in FIG. In this case, the active material layer usually contains both the solid electrolyte material and the active material described above. The ratio of the active material and the solid electrolyte material in the active material layer is preferably such that the solid electrolyte material is in the range of 1 to 1000 parts by volume when the active material is 100 parts by volume. More preferably, it is in the range of 100 parts by volume to 100 parts by volume. This is because if the proportion of the solid electrolyte material is too small, the ionic conductivity of the active material layer may be lowered, and if the proportion of the solid electrolyte material is too large, the capacity of the active material layer may be lowered. . Note that the content of the active material in the active material layer, the thickness of the active material layer, the filling rate, and the like are the same as described above.

  The sintered body for a battery according to the present invention has a theoretical discharge capacity of the active material when an evaluation battery having an active material layer containing the solid electrolyte material and the active material and a Li metal layer is produced. The battery is preferably fired at a temperature at which an evaluation battery having a discharge capacity of 30% or more can be obtained. This is because a different phase is formed to such an extent that good charge / discharge characteristics can be obtained.

Here, the evaluation battery is produced as follows. First, a pellet-shaped intermediate containing the solid electrolyte material and the active material is prepared. The proportions of the solid electrolyte material and the active material can be appropriately adjusted according to the purpose, but typically, the two materials are mixed so as to have the same volume to produce a pellet. Next, the obtained pellet is fired at a predetermined temperature for 2 hours to obtain a sintered body for evaluation. The sintered body for evaluation was pulverized in a mortar and mixed as a sintered body for evaluation: carbon black: PTFE = 70: 25: 5 as an electrode, a Li metal layer as a counter electrode, and an electrolyte. A battery for evaluation is prepared using a solution in which LiPF ₆ is dissolved at 1 mol / L in a solvent mixed at a volume ratio of EC: DEC = 1: 2. This evaluation battery is charged and discharged under the conditions of a current of 0.2 mA and a voltage range of 1.0 V to 3.0 V. Here, since the first discharge capacity is greatly affected by the irreversible reaction, the second discharge capacity is defined as the discharge capacity of the evaluation battery. On the other hand, the theoretical discharge capacity of the active material is calculated by dividing the number of Li reactions per mole by the molecular weight of the material. Then, various firing temperatures are changed, and a temperature range in which the discharge capacity of the evaluation battery is 30% or more with respect to the theoretical discharge capacity of the active material is determined. The sintered body for a battery of the present invention is preferably fired in the temperature range thus determined.

  In addition, the battery sintered body of the present invention is preferably fired at a temperature in the range of 510 ° C to 650 ° C, and preferably fired at a temperature in the range of 550 ° C to 650 ° C. It is more preferable that This is because a different phase is formed to such an extent that good charge / discharge characteristics can be obtained.

  Further, the battery sintered body may be in the form of a pellet or a sheet. As the shape of the battery sintered body, the same shape as that of various existing sintered bodies can be used. Examples thereof include a columnar shape, a flat plate shape, and a cylindrical shape.

B. Next, the all solid lithium battery of the present invention will be described. The all-solid-state lithium battery of the present invention is characterized by having the above-described sintered body for a battery.

  FIG. 3 is a schematic cross-sectional view showing an example of the all solid lithium battery of the present invention. 3 includes a positive electrode active material layer 101, a negative electrode active material layer 102, a solid electrolyte layer 103 formed between the positive electrode active material layer 101 and the negative electrode active material layer 102, and a positive electrode active material. A positive electrode current collector 104 that collects current from the layer 101, a negative electrode current collector 105 that collects current from the negative electrode active material layer 102, and a battery case 106 that houses these members are included. The all-solid-state lithium battery of the present invention is greatly characterized by having the above-described sintered body for a battery. For example, as shown in FIG. 1, when the battery sintered body 10 is a laminate of the solid electrolyte layer 11 and the active material layer 12, the active material layer 12 is the positive electrode active material layer 101 in FIG. Alternatively, the negative electrode active material layer 102 may be used. Similarly, as shown in FIG. 2, when the battery sintered body is the active material layer 12, the active material layer 12 may be the positive electrode active material layer 101 in FIG. 102 may be sufficient.

According to this invention, it can be set as the all-solid-state lithium battery with favorable charging / discharging characteristics by using the sintered compact for batteries mentioned above.
Hereinafter, the all-solid lithium battery of the present invention will be described for each configuration.

1. Positive electrode active material layer The positive electrode active material layer in the present invention is a layer containing at least a positive electrode active material, and may contain at least one of a conductive material, a solid electrolyte material, and a binder as necessary. good. When the above-described active material for a battery sintered body (an active material containing Li, Ti, O) is used as a negative electrode active material, examples of the positive electrode active material include LiCoO ₂ , LiMnO ₂ , Li ₂ NiMn _3. O ₈ , LiVO ₂ , LiCrO ₂ , LiFePO ₄ , LiCoPO ₄ , LiNiO ₂ , LiNi _1/3 Co _1/3 Mn _1/3 O _2, or the like can be used.

  The positive electrode active material layer in the present invention may further contain a conductive material. By adding a conductive material, the conductivity of the positive electrode active material layer can be improved. Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. The positive electrode active material layer may further contain a solid electrolyte material. By adding the solid electrolyte material, the Li ion conductivity of the positive electrode active material layer can be improved. Examples of the solid electrolyte material include an oxide solid electrolyte material and a sulfide solid electrolyte material. The positive electrode active material layer may further contain a binder. Examples of the binder include fluorine-containing binders such as polytetrafluoroethylene (PTFE). The thickness of the positive electrode active material layer is preferably in the range of 0.1 μm to 1000 μm, for example.

2. Negative electrode active material layer The negative electrode active material layer in the present invention is a layer containing at least a negative electrode active material, and may contain at least one of a conductive material, a solid electrolyte material, and a binder as necessary. good. When the above-described active material of a sintered body for a battery (active material containing Li, Ti, O) is used as a positive electrode active material, for example, a metal active material and a carbon active material are used as the negative electrode active material. Can do. Examples of the metal active material include In, Al, Si, and Sn. On the other hand, examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon.

  The conductive material, the solid electrolyte material, and the binder used for the negative electrode active material layer are the same as those in the positive electrode active material layer described above. Moreover, it is preferable that the thickness of a negative electrode active material layer exists in the range of 0.1 micrometer-1000 micrometers, for example.

3. Solid electrolyte layer The solid electrolyte layer in the present invention contains a solid electrolyte material, and may contain a binder as necessary. When the above-described sintered body for a battery is an active material layer (in the case of FIG. 2 described above), any solid electrolyte material having Li ion conductivity can be used for the solid electrolyte layer. Examples of the solid electrolyte material include an oxide solid electrolyte material and a sulfide solid electrolyte material.

  In addition, about the binder used for a solid electrolyte layer, it is the same as that of the case in the positive electrode active material layer mentioned above. Moreover, it is preferable that the thickness of a solid electrolyte layer exists in the range of 0.1 micrometer-1000 micrometers, for example.

4). Other Configurations The all solid lithium battery of the present invention has at least the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer described above. Furthermore, it usually has a positive electrode current collector for collecting current of the positive electrode active material layer and a negative electrode current collector for collecting current of the negative electrode active material layer. Examples of the material for the positive electrode current collector include SUS, aluminum, nickel, iron, titanium, and carbon. Among them, SUS is preferable. On the other hand, examples of the material for the negative electrode current collector include SUS, copper, nickel, and carbon. Of these, SUS is preferable. In addition, the thickness and shape of the positive electrode current collector and the negative electrode current collector are preferably selected as appropriate according to the application of the all solid lithium battery. Moreover, the battery case of a general all solid lithium battery can be used for the battery case used for this invention. Examples of the battery case include a SUS battery case.

5. All-solid lithium battery In the present invention, the active material of the sintered body for a battery is preferably used as the negative electrode active material. It is because it can be set as the all-solid-state lithium battery with high temperature durability. Furthermore, in the all solid lithium battery of the present invention, at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer may be a sintered body, and two of the above may be a sintered body. All of the above may be a sintered body.

  Further, the all solid lithium battery of the present invention may be a primary battery or a secondary battery, but among them, a secondary battery is preferable. This is because it can be repeatedly charged and discharged and is useful, for example, as an in-vehicle battery. Examples of the shape of the all solid lithium battery of the present invention include a coin type, a laminate type, a cylindrical type, and a square type. Moreover, the manufacturing method of the all-solid-state lithium battery of this invention will not be specifically limited if it is a method which can obtain the all-solid-state lithium battery mentioned above.

C. Next, a method for producing a battery sintered body according to the present invention will be described. The method for producing a sintered body for a battery according to the present invention comprises a solid electrolyte material represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), Li, Ti, and O. An intermediate preparation step for preparing an intermediate containing an active material contained therein, and the solid electrolyte material and the active material at the interface between the solid electrolyte material and the active material when analyzed by an X-ray diffraction method; A firing step of firing the intermediate at a temperature at which components other than the material are detected.

FIG. 4 is a schematic cross-sectional view showing an example of a method for producing a sintered body for a battery according to the present invention. In FIG. 4, first, a solid electrolyte layer 11X containing Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ which is a solid electrolyte material, and Li ₄ Ti ₅ O ₁₂ which is an active material material. A laminated body (intermediate body 10X) having the active material layer 12X to be contained is prepared (FIG. 4A). Thereafter, the intermediate 10 </ b> X is fired at a predetermined temperature to obtain a battery sintered body 10 that is a laminate (FIG. 4B).

FIG. 5 is a schematic cross-sectional view showing another example of the method for producing a sintered body for a battery according to the present invention. In FIG. 5, first, an active material layer 12X containing Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ that is a solid electrolyte material and Li ₄ Ti ₅ O ₁₂ that is an active material material. (Intermediate body 10X) is prepared (FIG. 5A). Thereafter, the intermediate 10X is fired at a predetermined temperature, whereby the battery sintered body 10 that is the active material layer 12 is obtained (FIG. 5B).

According to the present invention, a solid electrolyte material represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), and an active material containing Li, Ti, and O By using in combination, it is possible to obtain a sintered body for a battery that can exhibit good charge / discharge characteristics even when a different phase is generated at the interface between the two.
Hereinafter, the manufacturing method of the sintered body for a battery according to the present invention will be described step by step.

1. Intermediate Preparation Step The intermediate preparation step in the present invention comprises a solid electrolyte material represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), Li, Ti, and O. This is a step of preparing an intermediate containing an active material to be contained.

The composition, shape, and the like of the solid electrolyte material contained in the intermediate are the same as those described in “A. Battery sintered body”. In particular, the solid electrolyte material contained in the intermediate is preferably Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ .

The composition, shape, and the like of the active material contained in the intermediate are the same as those described in “A. Battery sintered body”. In particular, the active material contained in the intermediate is preferably Li ₄ Ti ₅ O ₁₂ .

  The structure of the intermediate body differs depending on the structure of the intended battery sintered body. For example, as shown in FIG. 4B, when obtaining a battery sintered body that is a laminate, an intermediate of the laminate is prepared. Each of the solid electrolyte layer and the active material layer constituting the intermediate is preferably in the form of a pellet. Moreover, what pelletized simultaneously the powder material for forming a solid electrolyte layer and the powder material for forming an active material layer may be used. On the other hand, as shown in FIG. 5B, when obtaining a battery sintered body that is an active material layer, an intermediate of the active material layer is prepared. The active material layer constituting the intermediate is preferably in the form of pellets.

2. Firing step The firing step in the present invention is a temperature at which components other than the solid electrolyte material and the active material are detected at the interface between the solid electrolyte material and the active material when analyzed by X-ray diffraction. This is a step of firing the intermediate.

  The firing temperature for firing the intermediate is not particularly limited as long as it is a temperature at which components other than the solid electrolyte material and the active material can be detected, but is preferably lower. This is because the process cost can be reduced. In addition, when the battery for evaluation having the solid electrolyte material and the active material layer containing the active material, and the Li metal layer is manufactured, the firing temperature is the theoretical discharge capacity of the active material. It is preferable that the temperature is such that an evaluation battery having a discharge capacity of 30% or more can be obtained. This is because a different phase is formed to such an extent that good charge / discharge characteristics can be obtained.

  The firing temperature varies depending on the type of the solid electrolyte material and the active material, but is preferably 510 ° C. or higher, and more preferably 550 ° C. or higher. This is because if the firing temperature is too low, a sintered body may not be obtained. On the other hand, it is preferable that the said baking temperature is 650 degrees C or less, for example. This is because if the firing temperature is too high, the charge / discharge characteristics may be greatly reduced.

  The firing time for firing the intermediate is not particularly limited as long as a desired battery sintered body can be obtained. Examples of the method for firing the intermediate include a method using a firing furnace. Examples of the atmosphere during firing include an air atmosphere and an inert atmosphere, and an inert atmosphere is preferable. This is because an unnecessary oxidation reaction can be prevented. Examples of the inert atmosphere include an argon atmosphere and a nitrogen atmosphere.

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

  Hereinafter, the present invention will be described in more detail with reference to examples.

[Example 1]
First, Li ₄ Ti ₅ O ₁₂ (Ishihara Sangyo Co., Ltd., LTO) and glassy Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (Hosokawa Micron Corp., LAGP) are used as LTO: The mixture was mixed at a volume ratio of LAGP = 50: 50. Next, 1 g of the obtained mixture was pressed to prepare a 13 mm diameter pellet (intermediate). Next, the obtained pellet was baked under conditions of an air atmosphere and 650 ° C. for 2 hours to obtain a sintered body for a battery.

[Examples 2 and 3]
A sintered body for a battery was obtained in the same manner as in Example 1 except that the firing temperature was changed to 600 ° C. and 550 ° C., respectively.

[Comparative Example 1]
A comparative sample was obtained in the same manner as in Example 1 except that the firing temperature was changed to 500 ° C.

[Comparative Example 2]
The intermediate prepared in Example 1 was used as a comparative sample.

[Evaluation]
(X-ray diffraction measurement)
The samples obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were pulverized in a mortar, and X-ray diffraction (XRD) measurement was performed. For XRD measurement, RIG Ultimate III made by Rigaku was used, and CuKα rays were used. The result is shown in FIG. As shown in FIG. 6 (e), only the LTO crystal peak was observed in the sample that was not fired, and the glassy LAGP peak was not confirmed. On the other hand, as shown in FIGS. 6A to 6D, in Examples 1 to 3 and Comparative Example 1, a large crystal peak was confirmed in the vicinity of 2θ = 26 °. It was a crystal peak not assigned to LAGP, and it was confirmed that a heterogeneous phase was generated at the interface between LTO and LAGP. Note that the peak near 2θ = 26 ° may be a crystal peak of TiO ₂ . Moreover, although the comparative example 1 performed baking at 500 degreeC, sintering of LAGP did not advance and it was not a sintered compact.

(Differential heat and thermogravimetric measurement)
The sample obtained in Comparative Example 2 was subjected to differential thermal and thermogravimetric simultaneous measurement (TG / DTA). The result is shown in FIG. As shown in FIG. 7, a peak was confirmed at around 450 ° C., suggesting the possibility that a heterogeneous phase was generated by firing at 450 ° C. or higher.

(Charge / discharge characteristics)
An evaluation battery was prepared using the sample obtained in Example 3 (firing at 550 ° C.). The sample obtained in Example 3 was pulverized in a mortar, and a sample: carbon black: PTFE = 70: 25: 5 mixed at a weight ratio was used as an electrode, a Li metal layer was used as a counter electrode, and EC was used as an electrolyte. A battery for evaluation was produced using a solution obtained by dissolving LiPF ₆ at a concentration of 1 mol / L in a solvent mixed at a volume ratio of DEC = 1: 2. This evaluation battery was charged and discharged under the conditions of a current of 0.2 mA and a voltage range of 1.0 V to 3.0 V. The results are shown in FIG.

  As shown in FIG. 8 and Table 1, it was confirmed that charging / discharging was possible. The second discharge capacity was 74 mAh / g. Since the theoretical discharge capacity of LTO is 202 mAh / g, it was confirmed that the evaluation battery had a discharge capacity of 36.6% with respect to the theoretical discharge capacity of LTO. Moreover, when the battery for evaluation was similarly produced using the sample obtained in Example 1, 2, it was confirmed similarly that it has a discharge capacity of 30% or more with respect to the theoretical discharge capacity of LTO. Thus, although the battery sintered body obtained in the examples had a different phase, it was confirmed that it was sufficiently chargeable / dischargeable and useful for an all-solid lithium battery.

DESCRIPTION OF SYMBOLS 1 ... Solid electrolyte material 2 ... Active material material 3 ... Different phase 10 ... Battery sintered body 10X ... Intermediate body 11 ... Solid electrolyte layer 12 ... Active material layer 100 ... All solid lithium battery

Claims (11)

A solid electrolyte material represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), and an active material containing Li, Ti, and O,
A sintered body for a battery, wherein components other than the solid electrolyte material and the active material are detected at an interface between the solid electrolyte material and the active material when analyzed by an X-ray diffraction method. The sintered body for a battery according to claim 1, wherein the active material is Li ₄ Ti ₅ O ₁₂ .   When an evaluation battery having an active material layer containing the solid electrolyte material and the active material, and a Li metal layer is fabricated, a discharge capacity of 30% or more with respect to the theoretical discharge capacity of the active material The battery sintered body according to claim 1 or 2, wherein the battery sintered body is fired at a temperature at which the evaluation battery is obtained.   The sintered body for a battery according to any one of claims 1 to 3, wherein the sintered body is fired at a temperature within a range of 550 ° C to 650 ° C.   The battery sintered body according to any one of claims 1 to 4, wherein the battery sintered body is an active material layer containing the solid electrolyte material and the active material.   The solid electrolyte layer containing the solid electrolyte material, and the active material layer formed on the solid electrolyte layer and containing the active material material. The sintered body for a battery according to claim 1.   An all solid lithium battery comprising the battery sintered body according to any one of claims 1 to 6. An intermediate containing a solid electrolyte material represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2) and an active material containing Li, Ti, and O is prepared. Intermediate preparation step,
A firing step of firing the intermediate at a temperature at which components other than the solid electrolyte material and the active material are detected at the interface between the solid electrolyte material and the active material when analyzed by an X-ray diffraction method When,
The manufacturing method of the sintered compact for batteries characterized by having. The method for producing a sintered body for a battery according to claim 8, wherein the active material is Li ₄ Ti ₅ O ₁₂ .   When an evaluation battery having an active material layer containing the solid electrolyte material and the active material and a Li metal layer is produced at a firing temperature in the firing step, the theoretical discharge capacity of the active material is The method for producing a sintered body for a battery according to claim 8 or 9, wherein the temperature is such that an evaluation battery having a discharge capacity of 30% or more can be obtained.   The method for producing a battery sintered body according to any one of claims 8 to 10, wherein a firing temperature in the firing step is within a range of 550C to 650C.

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