JP2014053166A - Sintered body for battery, all solid state lithium battery, and method for producing sintered body for battery - Google Patents

Abstract

A main object of the present invention is to provide a sintered body for a battery exhibiting good thermal stability.
The present invention solves the above-mentioned problems by providing a sintered body for a battery characterized by containing an active material having a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ .
[Selection] Figure 6

Description

  The present invention relates to a sintered body for a battery that exhibits good thermal stability.

  With the rapid spread of information-related equipment and communication equipment such as personal computers, video cameras, and mobile phones in recent years, the development of batteries that are excellent as power sources has been regarded as important. In fields other than information-related equipment and communication-related equipment, for example, in the automobile industry, development of lithium batteries used for electric cars and hybrid cars is being promoted.

  Since lithium batteries currently on the market use an electrolyte containing a flammable organic solvent, it is possible to install safety devices that suppress the temperature rise during short circuits and to improve the structure and materials to prevent short circuits. Necessary. On the other hand, an all-solid lithium battery in which the electrolyte is changed to a solid electrolyte layer to make the battery all solid does not use a flammable organic solvent in the battery. It is considered to be excellent in productivity.

  Such all solid lithium batteries are usually formed between 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 positive electrode active material layer and a negative electrode active material layer. And a solid electrolyte layer. For example, Patent Document 1 discloses an all-solid lithium secondary battery having a positive electrode active material layer, a negative electrode active material layer, and a solid electrolyte layer, which is formed at the interface between the negative electrode active material layer and the solid electrolyte layer. An all-solid lithium secondary battery including at least one of one mixed region and a second mixed region formed at an interface between a positive electrode active material layer and a solid electrolyte layer is described. The first mixed region contains the constituent material of the negative electrode active material layer and the constituent material of the solid electrolyte layer, and the second mixed region includes the constituent material of the positive electrode active material layer and the solid electrolyte layer. And a constituent material.

Moreover, in patent document 2, it is a lithium secondary battery with which the solid electrolyte sheet was provided between the positive electrode and the negative electrode, Comprising: From the solid electrolyte sheet and the gel electrolyte laminated | stacked on both surfaces of the hard electrolyte sheet It is described that it becomes. In Patent Document 2, a lithium phosphate compound such as Li ₃ In ₂ (PO ₄ ) ₃ is cited as an example of a hard material constituting the hard electrolyte sheet.

JP 2008-251225 A JP 2004-171995 A

  Good thermal stability is required for members used in batteries. In view of the above circumstances, the main object of the present invention is to provide a sintered body for a battery that exhibits good thermal stability.

In order to solve the above-described problems, the present invention provides a sintered body for a battery characterized by containing an active material having a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ .

According to the present invention, since Li ₃ In ₂ (PO ₄ ) ₃ has high thermal stability, a sintered body for a battery that exhibits good thermal stability can be obtained.

  In the said invention, it is preferable that the sintered compact for batteries further contains the solid electrolyte material which is a NASICON type phosphoric acid compound. This is because Li ion conductivity can be improved.

In the said invention, it is preferable that the said solid electrolyte material is a compound represented by following General formula (1).
Li _{1 + x} M1 _x M2 _2-x (PO ₄ ) ₃ (1)
(In the above formula (1), M1 is at least one selected from the group consisting of Al, Y, Ga and In, M2 is at least one selected from the group consisting of Ti, Ge and Zr, and x Is 0 ≦ x ≦ 2.)

In the said invention, it is preferable that the said solid electrolyte material is a compound represented by following General formula (2).
Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (2)
(In the above formula (2), 0 ≦ x ≦ 2)

  In the above invention, the active material preferably has an In crystal phase. This is because the presence of the In crystal phase can lower the overall potential.

  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 which shows favorable thermal stability by using the sintered compact for batteries mentioned above.

Further, in the present invention, an intermediate preparation step of preparing an intermediate containing an In-containing active material and a solid electrolyte material that is one of an amorphous phosphate compound and a NASICON phosphate compound, A sintered body for a battery, characterized by having a firing process for firing the intermediate and forming a sintered body for a battery containing an active material having a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ A manufacturing method is provided.

According to the present invention, since Li ₃ In ₂ (PO ₄ ) ₃ has high thermal stability, it is possible to obtain a battery sintered body exhibiting good thermal stability.

  The sintered body for a battery of the present invention has an effect that the thermal stability is good.

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 explaining 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 diagram which shows an example of the manufacturing method of the sintered compact for batteries of this invention. 2 is an XRD pattern of a battery sintered body obtained in Example 1. FIG. It is a result of TG-DTA with respect to the mixture of glassy LAGP and In powder used in Example 1. 3 is a result of CV measurement for the evaluation battery obtained in Example 2. FIG. 6 is a graph showing charge / discharge characteristics of an evaluation battery obtained in Comparative Example 1. 6 is a graph showing charge / discharge characteristics of an evaluation battery obtained in Comparative Example 2.

  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 First, the battery sintered body of the present invention will be described. The sintered body for a battery according to the present invention is characterized by containing an active material having a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ .

1 and 2 are schematic cross-sectional views illustrating the sintered body for a battery of the present invention. The battery sintered body 10 in FIG. 1 is an active material layer 11 containing an active material 1 having a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ and a solid electrolyte material 2. The active material 1 and the solid electrolyte material 2 are usually present in the active material layer 11 in a dispersed state. On the other hand, the battery sintered body 10 in FIG. 2 includes an active material layer 11 containing an active material 1 having a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ and a solid electrolyte layer containing a solid electrolyte material 2. 12. The active material layer 11 may further contain the solid electrolyte material 2.

In addition, the active material in the present invention has a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ . This crystal phase is formed by, for example, a reaction between an In-containing active material and a solid electrolyte material that is a phosphoric acid compound. This reaction will be described with reference to FIG. As shown in FIG. 3A, when In and LAGP (Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ ) are heat-treated under predetermined conditions, they react to form Li ₃ In ₂ (PO ₄ ) An active material 1 having _three crystal phases is obtained. In fact, it is presumed that a side reaction product derived from Al or Ge contained in LAGP is generated, but the presence of a crystal phase may not be confirmed and is not considered in FIG.

FIG. 3A illustrates a case where a sintered body containing the active material 1 having a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ is formed, and the crystal phases of In and LAGP are not confirmed. However, there are various cases depending on the ratio of In and LAGP and the heat treatment conditions. For example, as shown in FIG. 3B, when a part of In remains, a sintered body containing an active material 1 having a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ and In is formed, and LAGP The crystal phase may not be confirmed. On the contrary, as shown in FIG. 3C, when a part of LAGP remains, the active material 1 having the crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ and the solid electrolyte material having the crystal phase of LAGP 2 may be formed, and the In crystalline phase may not be confirmed. Further, as shown in FIG. 3D, when a part of In and LAGP respectively remain, the active material 1 having the crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ and In and the crystal phase of LAGP A sintered body with the solid electrolyte material 2 is formed.

According to the present invention, since Li ₃ In ₂ (PO ₄ ) ₃ has high thermal stability, a sintered body for a battery that exhibits good thermal stability can be obtained. In addition, Li ₃ In ₂ (PO ₄ ) ₃ causes a charge / discharge reaction in the vicinity of 1.3 V (vs. Li / Li ⁺ ) as shown in Examples described later, and thus is useful as a negative electrode active material, for example. _{Furthermore, Li 3 In 2 (PO 4} ) 3 , for example, obtained by heat treatment of In and LAGP. The change from In to Li ₃ In ₂ (PO ₄ ) ₃ by heat treatment indicates that Li ₃ In ₂ (PO ₄ ) ₃ has higher thermal stability than LA to In GP.
Hereinafter, each structure of the sintered body for a battery of the present invention will be described in detail.

(1) Active material The active material in the present invention has a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ . The presence of the crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ can be confirmed by an X-ray diffraction method or the like.

The active material in the present invention is not particularly limited as long as it has a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ . The active material may have a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ as a main phase. Note that “being a main phase” means that the ratio is the largest in the crystal phase functioning as an active material. Furthermore, the active material may have substantially only Li ₃ In ₂ (PO ₄ ) ₃ . On the other hand, the active material may have another crystal phase that functions as an active material in addition to Li ₃ In ₂ (PO ₄ ) ₃ . Examples of the other crystal phase include a crystal phase of an In-containing active material, which will be described later, and an In crystal phase is particularly preferable. This is because the potential of In is lower than the potential of Li ₃ In ₂ (PO ₄ ) ₃ and the overall potential can be lowered. As a result, for example, an active material useful as a negative electrode active material can be obtained.

(2) Solid Electrolyte Material The battery sintered body of the present invention preferably further contains a solid electrolyte material that is a NASICON type phosphoric acid compound. This is because Li ion conductivity can be improved. Here, “Nashikon type” means one having a NASICON type crystal structure. Furthermore, “having a NASICON crystal structure” means not completely amorphous, and includes not only completely crystalline but also amorphous and crystalline intermediate states. That is, the NASICON type phosphoric acid compound only needs to have crystallinity whose peak can be confirmed by an X-ray diffraction method.

The solid electrolyte material is not particularly limited as long as it is a NASICON type phosphoric acid compound. For example, in the general formula (1) Li _{1 + x} M1 _x M2 _2-x (PO ₄ ) ₃ (in the formula (1) , M1 is at least one selected from the group consisting of Al, Y, Ga and In, M2 is at least one selected from the group consisting of Ti, Ge and Zr, and x is 0 ≦ x ≦ 2. It is preferably a NASICON type phosphoric acid compound represented by:

Among the above, the metal of M1 is preferably at least one selected from the group consisting of Al, Y and Ga, and more preferably Al. The metal of M2 is preferably at least one selected from the group consisting of Ge and Ti, more preferably Ge. That is, a NASICON type phosphoric acid compound (LAGP) represented by the general formula (2) Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (in the formula (2), 0 ≦ x ≦ 2) preferable. This is because the compound represented by the above formula (2) among the NASICON type phosphoric acid compounds has high ion conductivity.

Further, among the above, the range of x is preferably 0.1 ≦ x ≦ 1.9, and more preferably 0.3 ≦ x ≦ 0.7. In particular, the solid electrolyte material is _preferably Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ in the above formula.

  For example, as shown in FIG. 1, when the active material layer 11 contains the active material 1 and the solid electrolyte material 2, the ratio of the active material to the total of the active material and the solid electrolyte material is, for example, 30% by volume. It is preferable that it is above, more preferably in the range of 50% by volume to 99% by volume, and still more preferably in the range of 70% by volume to 90% by volume.

(3) Battery Sintered Body In the present invention, the “battery sintered body” means an object used in a battery and sintered by firing. Here, “sintering” refers to a phenomenon in which a solid powder aggregate is heated to become a dense object. The battery sintered body is not particularly limited as long as it is a sintered body used as a battery member. Here, “sintered body” refers to a dense body solidified by heating an aggregate of solid powders. Usually, the sintered body has a density (filling rate, porosity) that cannot be reached by compaction 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.

  As an example of the structure of the battery sintered body of the present invention, as shown in FIG. 1, a battery sintered body 10 that is an active material layer 11 can be cited. Although the thickness of an active material layer is not specifically limited, For example, it exists in the range of 5 micrometers-0.1 mm, and it is preferable that it exists in the range of 10 micrometers-0.05 mm. The porosity of the active material layer is, for example, 15% or less, and preferably in the range of 5% to 10%.

  As another example of the structure of the sintered body for a battery of the present invention, a laminate including an active material layer 11 and a solid electrolyte layer 12 can be given as shown in FIG. Although the thickness of the solid electrolyte layer in a laminated body is not specifically limited, For example, it exists in the range of 1 micrometer-0.1 mm, and it is preferable that it exists in the range of 2 micrometers-0.05 mm. The porosity of the solid electrolyte layer is, for example, 20% or less, and preferably 10% or less. Note that the thickness and porosity of the active material layer in the laminate are the same as described above. When the battery sintered body is a laminated body, the laminated body may have an active material layer on one surface of the solid electrolyte layer, and the active material layers ( It may have a positive electrode active material layer and a negative electrode active material layer. In the latter case, the battery sintered body can be used as a battery power generation element as it is.

  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.

  The method for producing a sintered body for a battery according to the present invention is not particularly limited as long as it is a method capable of obtaining the above-described sintered body for a battery. For example, “C. The method described in the section “Manufacturing method” can be mentioned.

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. 4 is a schematic cross-sectional view showing an example of the all solid lithium battery of the present invention. The all-solid lithium battery 20 shown in FIG. 4 has a positive electrode active material layer 21, a negative electrode active material layer 22, and a solid electrolyte layer 23 formed between the positive electrode active material layer 21 and the negative electrode active material layer 22. . The present invention is greatly characterized in that the above-described sintered body for a battery is used. For example, as shown in FIG. 1, when the battery sintered body 10 is the active material layer 11, the active material layer 11 may be the positive electrode active material layer 21 in FIG. There may be. For example, as shown in FIG. 2, when the battery sintered body 10 is a laminate of the active material layer 11 and the solid electrolyte layer 12, the laminate is composed of the positive electrode active material layer 21 and the solid electrolyte layer in FIG. 4. 23, or a laminate of the negative electrode active material layer 22 and the solid electrolyte layer 23.

According to this invention, it can be set as the all-solid-state lithium battery which shows favorable thermal stability 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. The positive electrode active material may be an active material used in the above-described battery sintered body, or may be another positive electrode active material used in a general lithium battery.

In the case where the above-described active material of a sintered body for a battery is used as a negative electrode active material, the positive electrode active material is appropriately selected according to the type of the all-solid lithium battery to be used. Examples include substances and olivine type active materials. Specifically, LiCoO ₂ , LiNiO ₂ , LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiVO ₂ , LiCrO ₂ , LiMn ₂ O ₄ , Li (Ni _0.25 Mn _0.75 ) ₂ O ₄ , LiCoMnO ₄ , Li ₂ NiMn ₃ O ₈ , LiCoPO ₄ , LiMnPO ₄ , LiFePO _{4 and the} like.

  The positive electrode active material layer in the present invention may further contain at least one of a conductive material, a binder, and a solid electrolyte material, if necessary, in addition to the positive electrode active material. When the positive electrode active material layer contains a conductive material, the conductivity of the positive electrode active material layer can be improved. Examples of such a conductive material include carbon fibers such as acetylene black, ketjen black, and VGCF, graphite, and the like. The binder is not particularly limited as long as it is chemically and electrically stable. For example, a fluorine-containing binder such as polyvinylidene fluoride (PVdF) or polytetrafluoroethylene (PTFE). Materials, rubber binders such as styrene butadiene rubber (SBR), polyimide binders, cellulose binders such as carboxymethylcellulose (CMC), and the like. The solid electrolyte material is not particularly limited as long as it has desired ionic conductivity, and examples thereof include oxide solid electrolyte materials and sulfide solid electrolyte materials. The solid electrolyte material will be described in detail in the section “3. Solid electrolyte layer” described later.

  The content of the positive electrode active material in the positive electrode active material layer is preferably higher from the viewpoint of capacity, for example, in the range of 60 wt% to 99 wt%, particularly in the range of 70 wt% to 95 wt%. Is preferred. Moreover, although the thickness of a positive electrode active material layer changes greatly with the structure of the target all-solid-state lithium battery, it is preferable to exist in the range of 0.1 micrometer-1000 micrometers, 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. The negative electrode active material may be an active material used in the above-described battery sintered body, or may be another negative electrode active material used in a general lithium battery.

  In the case where the above-described active material of the sintered body for a battery is used as the positive electrode active material, the negative electrode active material is appropriately selected according to the type of the target all-solid lithium battery. And carbon active materials. Examples of the metal active material include In, Al, Si, and Sn. Examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, Examples include soft carbon.

  In addition to the negative electrode active material, the negative electrode active material layer may contain at least one of a conductive material, a solid electrolyte material, and a binder as necessary. Note that the conductive material, the solid electrolyte material, and the binder are the same as those used for the positive electrode active material layer described above. Moreover, although the thickness of a negative electrode active material layer changes greatly with the structure of the target all-solid-state lithium battery, it is preferable to exist in the range of 0.1 micrometer-1000 micrometers, for example.

3. Solid electrolyte layer The solid electrolyte layer in the present invention is a layer containing at least a solid electrolyte material, and may contain a binder as necessary. The solid electrolyte material may be a solid electrolyte material in the above-described sintered body for a battery, or may be a general solid electrolyte material having Li ion conductivity.

The solid electrolyte material is not particularly limited as long as it has Li ion conductivity, and examples thereof include an oxide solid electrolyte material and a sulfide solid electrolyte material. Specifically, examples of the oxide solid electrolyte material having Li ion conductivity include Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 2), Li _{1 + x} Al _x Ti _2-x ( PO ₄ ) ₃ (0 ≦ x ≦ 2), LiLaTiO (eg, Li _0.34 La _0.51 TiO ₃ ), LiPON (eg, Li _2.9 PO _3.3 N _0.46 ), LiLaZrO (eg, Li ₇ La ₃ Zr ₂ O ₁₂ ) and the like. Examples of the sulfide solid electrolyte material having Li ion conductivity include Li ₂ S—P ₂ S ₅ compound and Li ₂ S—GeS ₅ compound.

  The thickness of the solid electrolyte layer varies greatly depending on the type of the solid electrolyte material and the configuration of the all-solid lithium battery. For example, the thickness is in the range of 0.1 μm to 1000 μm, and in particular in the range of 0.1 μm to 300 μm. It is preferable.

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. The material of the current collector is not particularly limited as long as it has electronic conductivity, and examples thereof include SUS, aluminum, copper, nickel, titanium, iron, and carbon. Examples of the shape of the current collector include a foil shape, a mesh shape, and a porous shape. 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-state lithium battery The all-solid-state lithium battery of the present invention may be a sintered body in which at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer is a sintered body. It may be, and all of the above may be a sintered body.

  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 such an all solid lithium battery include a coin type, a laminate type, a cylindrical type, and a square type. 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 form the all-solid-state lithium battery mentioned above.

C. Next, a method for producing a sintered body for a battery according to the present invention will be described. The method for producing a sintered body for a battery according to the present invention is an intermediate for preparing an intermediate including an In-containing active material and a solid electrolyte material that is one of an amorphous phosphoric acid compound and a NASICON type phosphoric acid compound. A body preparation step, and a firing step of firing the intermediate and forming a sintered body for a battery containing an active material having a crystal phase of Li ₃ In ₂ (PO ₄ ) _3. To do.

FIG. 5 is a schematic view showing an example of a method for producing a sintered body for a battery according to the present invention. In FIG. 5, first, In is used as an In-containing active material, glassy LAGP is used as an amorphous phosphate compound, and an intermediate in which In and LAGP are in contact with each other is prepared. Next, by firing the intermediate at a predetermined temperature, In and LAGP are reacted to obtain a sintered body for a battery containing an active material having a crystal phase of Li ₃ In ₂ (PO ₄ ) _3. .

According to the present invention, since Li ₃ In ₂ (PO ₄ ) ₃ has high thermal stability, it is possible to obtain a battery sintered body exhibiting good thermal stability.
Hereafter, each process of the manufacturing method of the sintered compact for batteries of this invention is demonstrated.

(1) Intermediate Preparation Step The intermediate preparation step in the present invention includes an intermediate containing an In-containing active material and a solid electrolyte material that is one of an amorphous phosphate compound and a NASICON type phosphate compound. It is a process to prepare.

  The In-containing active material contained in the intermediate is not particularly limited as long as it contains In, and examples thereof include In, In alloy, In oxide, In nitride, and In sulfide. Among them, In and In alloys are preferable. Examples of the In alloy include In—Al alloy, In—Sn alloy, In—Ag alloy, In—Pb alloy, In—Sb alloy, In—Bi alloy, In—Mg alloy, In— Examples thereof include a Ca-based alloy. Note that, for example, an In—Si-based alloy means an alloy containing at least In and Si, and may be an alloy composed only of In and Si, or may be an alloy containing another element. . The same applies to the above-described alloys other than the In—Si alloy. The In alloy may be a binary alloy or a multi-component alloy of three or more components.

  About the solid electrolyte material contained in an intermediate body, it is the same as that of the content described in the term of the above-mentioned "A. battery sintered compact". In the present invention, as the solid electrolyte material contained in the intermediate, not only a NASICON type phosphate compound but also an amorphous phosphate compound can be used. This amorphous phosphate compound is usually converted into a NASICON phosphate compound by heat treatment.

  The structure of the intermediate body differs depending on the structure of the intended battery sintered body. For example, as shown in FIG. 1, when the battery sintered body 10 that is the active material layer 11 is obtained, an intermediate of the active material layer is prepared. In this case, the intermediate (active material layer) contains both the In-containing active material and the solid electrolyte material described above. The ratio of the In-containing active material in the active material layer is not particularly limited, but is preferably in the range of 50% by volume to 90% by volume, for example, in the range of 70% by volume to 90% by volume. It is more preferable. The ratio of the In-containing 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 10 to 110 parts by weight when the In-containing active material is 100 parts by weight. More preferably, it is within the range of 50 parts by weight to 50 parts by weight. 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. .

  On the other hand, as shown in FIG. 2, when obtaining the battery sintered body 10 which is a laminate of the active material layer 11 and the solid electrolyte layer 12, an intermediate of the laminate is prepared. The ratio of the solid electrolyte material in the solid electrolyte layer of the laminate is not particularly limited, but is preferably 1% by volume or more, and more preferably 10% by volume or more, for example. The solid electrolyte layer may be a layer made only of the solid electrolyte material. The ratio of the In-containing active material in the active material layer of the laminate is the same as that described above. In addition, when an intermediate body is a laminated body, the layer which consists only of In containing active materials may be sufficient as an active material layer.

(2) Firing step The firing step in the present invention is a step of firing the intermediate and forming a battery sintered body containing an active material having a crystal phase of Li ₃ In ₂ (PO ₄ ) _3. .

The firing temperature of the intermediate is not particularly limited as long as it is equal to or higher than the temperature at which the In-containing active material and the solid electrolyte material contained in the intermediate can react. For example, when the solid electrolyte material contained in the intermediate is an amorphous phosphate compound, and the Li ion conductivity of the amorphous phosphate compound is relatively low, the firing temperature is the crystallization of the amorphous phosphate compound. It is preferable that the temperature is higher. Specifically, the solid electrolyte material is a compound represented by the general formula (2) Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (in the above formula (2), 0 ≦ x ≦ 2). In this case, the firing temperature is preferably equal to or higher than the crystallization temperature of the amorphous phosphate compound. This is because the crystallinity of the solid electrolyte material can be improved and the Li ion conductivity can be improved.

  The firing temperature of the intermediate is, for example, preferably 400 ° C. or higher, more preferably 570 ° C. or higher, and particularly preferably 600 ° C. or higher. Further, the higher the firing temperature, the higher the crystallinity of the solid electrolyte material and the higher the Li ion conductivity. Specifically, it is preferably 1000 ° C. or lower. This is because if the temperature is lower than the above temperature, a special electric furnace or the like is not required, and a wide soaking zone can be secured in the furnace, so that the heat is easily transmitted uniformly to the sample.

  The atmosphere for firing the intermediate is not particularly limited as long as it can provide a desired battery sintered body. For example, an inert atmosphere is preferable. This is because the side reaction can be suppressed and the control is easy. Examples of the inert atmosphere include an argon atmosphere and a nitrogen atmosphere.

  The time for firing the intermediate is not particularly limited as long as a desired sintered body for a battery can be obtained. Examples of the method for firing the intermediate include a method using a firing furnace.

  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]
(Preparation of sintered body for battery)
As the amorphous phosphoric acid compound, glassy Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (LAGP) was prepared. In powder was prepared as an In-containing active material. These were mixed with a mortar at a volume ratio of 50:50, and the resulting mixture was pressed and formed into a pellet. Next, the pellet was baked under an argon atmosphere at 600 ° C. for 2 hours. Thereby, the sintered compact for batteries was obtained.

[Evaluation 1]
(X-ray diffraction measurement)
The battery sintered body obtained in Example 1 was subjected to X-ray diffraction (XRD) measurement using CuKα rays. The result is shown in FIG. As shown in FIG. 6, in the battery sintered body obtained in Example 1, peaks indicating Li ₃ In ₂ (PO ₄ ) ₃ and In crystal phases were confirmed.

(Thermal analysis)
The glassy LAGP and In powder mixture used in Example 1 was subjected to simultaneous differential thermal and thermogravimetric measurement (TG-DTA) in an Ar atmosphere. The result is shown in FIG. As shown in FIG. 7, a peak indicating melting of In was confirmed near 156 ° C., and a peak indicating crystallization of LAGP was confirmed near 570 ° C. Further, in the vicinity of 400 ° C., the reaction of the LAGP and In, _i.e., a peak showing the synthesis of _{Li 3 In 2 (PO 4)} 3 was confirmed.

[Example 2]
(Preparation of sintered body for battery)
First, glassy Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (LAGP) was added to a φ13 mm die and pressed to produce a solid electrolyte layer composed of LAGP. . Next, an In / LAGP mixed powder (in molar ratio, In / LAGP = 8.8) is disposed on one surface of the solid electrolyte layer, and a LiFePO ₄ / LAGP / C composite is disposed on the other surface of the solid electrolyte layer. The powder was placed and compacted. Next, cold isostatic pressing (CIP) was performed at 200 MPa for 1 minute to obtain a three-layer green compact. The obtained three-layer green compact was fired under an argon atmosphere, 600 ° C., and 2 hours. This obtained the sintered compact for batteries (evaluation battery, sintered battery).

The obtained evaluation battery was subjected to cyclic voltammetry (CV) measurement under the conditions of 0.1 mV / sec, 0 V to 3.5 V, and 3 cycles. The result is shown in FIG. As shown in FIG. 8, it was confirmed that the obtained evaluation battery was charged / discharged in the vicinity of 2.1 V, which is the intersection with the x-axis. Considering the LiFePO ₄ of potential (3.4V vs.Li/Li _^+), the potential of the _{Li 3 In 2 (PO 4)} 3 is suggested to be around 1.3V (vs.Li/Li ⁺⁾ It was.

[Comparative Example 1]
As the amorphous phosphoric acid compound, glassy Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (LAGP) was prepared. LiCoO ₂ powder was prepared as an active material. These were mixed with a mortar at a volume ratio of 50:50, and the resulting mixture was pressed and formed into a pellet. Next, the pellets were fired under conditions of an air atmosphere and 600 ° C. for 2 hours. Thereby, the sintered compact for batteries was obtained. The battery sintered body was pulverized in a mortar, and the battery sintered body: carbon black: PTFE = 70: 25: 5 weight ratio was used as the working electrode, Li metal was used as the counter electrode, and EC: A battery for evaluation was produced using a non-aqueous electrolyte in which LiPF ₆ was dissolved at 1 mol / L in a solvent mixed at a volume ratio of DEC = 1: 2.

Although the charging / discharging test was done with respect to the obtained evaluation battery, as shown in FIG. 9, the evaluation battery obtained in Comparative Example 1 could not be charged / discharged. The reason is considered to be that LiCoO ₂ and LAGP reacted to form a heterogeneous phase.

[Comparative Example 2]
As the amorphous phosphoric acid compound, glassy Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (LAGP) was prepared. Li ₄ TiO ₁₂ powder was prepared as an active material. These were mixed with a mortar at a volume ratio of 50:50, and the resulting mixture was pressed and formed into a pellet. Next, the pellet was fired under conditions of an air atmosphere, 550 ° C., and 2 hours. Thereby, the sintered compact for batteries was obtained. An evaluation battery was obtained in the same manner as in Comparative Example 1 except that this battery sintered body was used.

When a charge / discharge test was performed on the obtained evaluation battery, as shown in FIG. 10, the evaluation battery obtained in Comparative Example 2 was chargeable / dischargeable. However, the potential of Li ₄ TiO ₁₂ was 1.8 V (vs. Li / Li ⁺ ), which was higher than that of Li ₃ In ₂ (PO ₄ ) ₃ .

DESCRIPTION OF SYMBOLS 1 ... Active material material 2 ... Solid electrolyte material 10 ... Battery sintered body 11 ... Active material layer 12 ... Solid electrolyte layer 20 ... All solid lithium battery 21 ... Positive electrode active material layer 22 ... Negative electrode active material layer 23 ... Solid electrolyte layer

Claims (7)

A sintered body for a battery, comprising an active material having a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ .   The sintered body for a battery according to claim 1, further comprising a solid electrolyte material which is a NASICON type phosphoric acid compound. The sintered body for a battery according to claim 2, wherein the solid electrolyte material is a compound represented by the following general formula (1).
Li _{1 + x} M1 _x M2 _2-x (PO ₄ ) ₃ (1)
(In the above formula (1), M1 is at least one selected from the group consisting of Al, Y, Ga and In, M2 is at least one selected from the group consisting of Ti, Ge and Zr, and x Is 0 ≦ x ≦ 2.) The sintered body for a battery according to claim 3, wherein the solid electrolyte material is a compound represented by the following general formula (2).
Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (2)
(In the above formula (2), 0 ≦ x ≦ 2)   5. The sintered body for a battery according to claim 1, wherein the active material has an In crystal phase. 6.   An all-solid-state lithium battery comprising the battery sintered body according to any one of claims 1 to 5. An intermediate preparation step of preparing an intermediate containing an In-containing active material and a solid electrolyte material that is one of an amorphous phosphate compound and a NASICON type phosphate compound;
Firing the intermediate, and forming a sintered body for a battery containing an active material having a crystal phase of Li ₃ In ₂ (PO ₄ ) ₃ ;
The manufacturing method of the sintered compact for batteries characterized by having.

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