JP2013229132A - Electrode sintered body and electrode sintered body manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode sintered body which retains a sintered density and exhibits high electron conductivity.SOLUTION: An electrode sintered body 10 contains a solid electrolyte material 2, an electrode active material 1, and a conductive assistant 3. The solid electrolyte material is at least one of a compound represented by the general formula LiAlGe(PO)(0≤x≤1), a compound represented by the general formula LiAlTi(PO)(0≤x≤1) and a compound represented by the general formula LiLaTiO(0≤x≤1, 0≤y≤1). The electrode active material is at least one of a compound represented by the general formula LiM(PO)(Mis at least one of V, Fe and Ti) and a compound represented by the general formula LiMPO(Mis at least one of Ni, Co and Fe). The volume content of the conductive assistant in the electrode sintered body is in the range from 5 vol.% to 10 vol.%. The electron conductivity of the electrode sintered body is 1.0×10S/cm or greater.

Description

  The present invention relates to an electrode sintered body that exhibits high electron conductivity while maintaining a sintered density.

  For example, since lithium batteries have high electromotive force and high energy density, they are widely used in the fields of information-related equipment and communication equipment. On the other hand, in the field of automobiles, development of electric vehicles and hybrid vehicles is urgently caused by environmental problems and resource problems, and lithium batteries are also being studied as power sources for these.

  Currently, various lithium batteries are being developed. For example, Patent Document 1 discloses a lithium battery using an electrolyte / electrode laminate including a solid electrolyte layer and an electrode layer sintered and bonded to the solid electrolyte layer. Patent Document 2 discloses a lithium battery using, as an electrode layer, a sintered body containing electrode active material particles having a predetermined coating layer in at least 30 area% of a grain boundary surrounding the electrode active material particles. Yes. In Patent Document 2, there are very few substances that inhibit ionic conduction at the electrode layer-solid electrolyte layer interface and the grain boundary between the electrode active material and the electrolyte material in the electrode, and large current charge and discharge is possible. It is intended to provide a lithium battery that can obtain high charge / discharge efficiency even at an operating current and has low manufacturing costs.

JP 2011-192606 A JP 2011-086610 A

  Here, from the viewpoint of improving electron conductivity, the electrode sintered body preferably contains a conductive additive in addition to the solid electrolyte material and the electrode active material. For example, Patent Documents 1 and 2 also describe that a conductive additive is contained together with the solid electrolyte material and the electrode active material. However, as in Patent Documents 1 and 2, when an electrode sintered body is simply prepared by containing a conductive additive, the addition of the conductive additive improves the electronic conductivity but decreases the sintered density. There's a problem. This invention is made | formed in view of the said situation, and it aims at providing the electrode sintered compact which shows high electronic conductivity, maintaining a sintered density.

In order to achieve the above object, in the present invention, an electrode sintered body including a solid electrolyte material, an electrode active material, and a conductive additive, wherein the solid electrolyte material has the general formula Li _{1 + x} Al _x Ge. A compound represented by _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1), a compound represented by the general formula Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1), and It is at least one compound represented by the general formula Li _x La _y TiO ₃ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1), and the electrode active material has the general formula Li ₃ M ¹ ₂ (PO ₄ ). ₃ (M ¹ is at least ^one of V, Fe and Ti) and a compound represented by the general formula LiM ² PO ₄ (M ² is at least one of Ni, Co and Fe) At least one selected from the above, and the solid electrolyte material To the total of the electrode active material and the conductive additive, the volume ratio of the conductive additive is in the range of 5 vol% to 10 vol%, the electron conductivity of the electrode sintered body 1.0 × 10 ^-4 S / cm or more The electrode sintered compact characterized by the above-mentioned is provided.

  According to the present invention, along with the above-described solid electrolyte material and electrode active material, by containing a conductive additive so as to satisfy a predetermined volume ratio, high electron conductivity can be achieved while sufficiently maintaining the sintered density. It can be set as the electrode sintered compact shown. Therefore, a battery having high electron conductivity can be produced by using the electrode sintered body of the present invention.

Further, in the present invention, a preparation step of obtaining a sintered body forming material by mixing a solid electrolyte material, an electrode active material, and a conductive additive, a sintering step of sintering the sintered body forming material, The solid electrolyte material is a compound represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1), the general formula Li It is represented by _{1 + x Al x Ti 2-} x (PO 4) 3 (0 ≦ x ≦ 1) compound represented by the general formula _{Li x La y TiO 3 (0} ≦ x ≦ 1,0 ≦ y ≦ 1) The electrode active material is a compound represented by the general formula Li ₃ M ¹ ₂ (PO ₄ ) ₃ (M ¹ is at least one of V, Fe, and Ti) and formula ^{LiM 2} _PO 4 ^(M 2 is Ni, Co, at least one Fe A volume ratio of the conductive assistant to the total of the solid electrolyte material, the electrode active material and the conductive assistant is 5% by volume to 10% by volume. %, And the electrode sintered body after the sintering step has an electron conductivity of 1.0 × 10 ⁻⁴ S / cm or more. To do.

  According to the present invention, along with the above-described solid electrolyte material and electrode active material, by mixing a conductive additive so as to satisfy a predetermined volume ratio, high electron conductivity can be achieved while sufficiently maintaining the sintered density. The electrode sintered body shown can be obtained.

  In this invention, there exists an effect that the electrode sintered compact which shows high electronic conductivity can be provided, maintaining a sintered density fully.

It is a schematic sectional drawing which shows an example of the electrode sintered compact of this invention. It is a schematic diagram explaining an example of the manufacturing method of the electrode sintered compact of this invention. It is a schematic diagram which shows an example of a structure of the battery for evaluation using the electrode sintered compact of this invention. It is a graph which shows the electronic conductivity and sintered density of the electrode sintered compact obtained by Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-7. It is a graph which shows the electronic conductivity and sintered density of the electrode sintered compact obtained by Examples 2-1 to 2-2 and Comparative Examples 2-1 to 2-2. It is a charging / discharging characteristic measurement result in the electrode sintered compact obtained in Example 1-1. It is a charging / discharging characteristic measurement result in the electrode sintered compact obtained in Example 1-3. It is a charging / discharging characteristic measurement result in the electrode sintered compact obtained by the comparative example 1-1. It is a charging / discharging characteristic measurement result in the electrode sintered compact obtained in Reference Example 1.

  Hereinafter, the electrode sintered body and the method for producing the electrode sintered body of the present invention will be described in detail.

A. Electrode Sintered Body The electrode sintered body of the present invention is an electrode sintered body including a solid electrolyte material, an electrode active material, and a conductive additive, and the solid electrolyte material has the general formula Li _{1 + x} Al _x Ge. A compound represented by _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1), a compound represented by the general formula Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1), and It is at least one compound represented by the general formula Li _x La _y TiO ₃ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1), and the electrode active material has the general formula Li ₃ M ¹ ₂ (PO ₄ ). ₃ (M ¹ is at least ^one of V, Fe and Ti) and a compound represented by the general formula LiM ² PO ₄ (M ² is at least one of Ni, Co and Fe) At least one selected from the group consisting of the solid electrolyte material and the electrode active material. To the sum of the quality and the conductive auxiliary agent, the volume ratio of the conductive additive is in the range of 5 vol% to 10 vol%, the electron conductivity of the electrode sintered body 1.0 × 10 ^-4 S / Cm or more.

  FIG. 1 is a schematic sectional view showing an example of an electrode sintered body of the present invention. As shown in FIG. 1, the electrode sintered body 10 includes an electrode active material 1, a solid electrolyte material 2, and a conductive additive 3. In addition, the conductive support agent 3 is contained so that a volume ratio may be in the range of 5 volume% to 10 volume% with respect to the total of the electrode active material 1, the solid electrolyte material 2, and the conductive support agent 3. .

  According to the present invention, along with the above-described solid electrolyte material and electrode active material, by containing a conductive additive so as to satisfy a predetermined volume ratio, high electron conductivity can be achieved while sufficiently maintaining the sintered density. It can be set as the electrode sintered compact shown. Therefore, a battery having high electron conductivity can be produced by using the electrode sintered body of the present invention.

  As described above, for example, Patent Document 2 discloses a battery having an electrode layer made of a sintered body of a mixed material containing one or more types of electrode active material particles and solid electrolyte particles, In addition, it is described that it contains a conductive aid as required. However, in this case, it is considered that it is difficult to ensure the electron conductivity while maintaining the sintered density sufficiently when the conductive assistant is simply mixed and fired (compact sintering). That is, if the content of the conductive auxiliary is too small, it is considered that the electron conductivity is lowered. On the other hand, if the content of the conductive auxiliary is too large, the sintered density is considered to be lowered. .

On the other hand, in the present invention, the sintering density is sufficiently maintained by containing a conductive aid so that the volume ratio is within a predetermined range together with the specific electrode active material and the solid electrolyte material. However, it can be set as the electrode sintered compact which shows high electronic conductivity.
Hereinafter, the electrode sintered body of the present invention will be described in detail.

1. Solid Electrolyte Material The solid electrolyte material in the present invention may be described as a compound represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1) (hereinafter referred to as LAGP). ), A compound represented by the general formula Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1) (hereinafter sometimes referred to as LATP), and the general formula Li _x It is at least one of compounds represented by La _y TiO ₃ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) (hereinafter sometimes referred to as LLTO).

  The solid electrolyte material does not react even when fired with an electrode active material described later, that is, does not generate a different phase. Therefore, excellent ion conductivity is exhibited in the obtained electrode sintered body. Furthermore, since the solid electrolyte material has good ion conductivity of the solid electrolyte material itself, an electrode sintered body excellent in ion conductivity can be obtained. Here, the heterogeneous phase refers to a compound having a crystal structure different from that of the solid electrolyte material and the electrode active material. Specifically, a decomposition product of the solid electrolyte material, a decomposition product of the electrode active material, a reaction product of the solid electrolyte material and the electrode active material, and the like can be given. In addition, about generation | occurrence | production of a different phase, as shown in the reference examples 2-4 mentioned later, it can confirm by performing an X-ray diffraction (XRD) measurement.

The LAGP is a compound represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1), and x in the general formula satisfies 0 ≦ x ≦ 1. Of these, Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ is preferred in the present invention.

The LATP is a compound represented by the general formula Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1), and x in the general formula satisfies 0 ≦ x ≦ 1. Of these, Li _1.5 Al _0.5 Ti _1.5 (PO ₄ ) ₃ is preferable in the present invention.

The LLTO is a compound represented by the general formula Li _x La _y TiO ₃ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1), and x in the above general formula satisfies 0 ≦ x ≦ 1. In addition, y in the above general formula only needs to satisfy 0 ≦ y ≦ 1, and in the present invention, Li _0.35 La _0.55 TiO ₃ is preferable.

  In addition, the solid electrolyte material in the present invention is preferably a substance that undergoes sintering at a relatively low temperature. Here, generally, sintering refers to a phenomenon in which a solid powder aggregate is solidified and becomes dense. It is considered that, by heating, solid powders are first bonded to grow particles (volume expansion), and further heated to become denser. Therefore, it is considered that whether or not the solid electrolyte material, which is a solid powder, is a substance that undergoes sintering, can be determined by the volume expansion coefficient associated with grain growth. The solid electrolyte material preferably has a volume expansion coefficient at 600 ° C. of 20% or more, more preferably 30% or more, and further preferably in the range of 30% to 45%. This is because sintering can be performed at a relatively low temperature, and generation of unnecessary side reactions between the solid electrolyte material and the electrode active material can be suppressed. In addition, as a measuring method of the said volume expansion coefficient, for example, high temperature XRD measurement is performed for every temperature, and an XRD chart is obtained. A method of calculating the expansion coefficient of each of the materials a, b, and c axes from the correlation between the lattice constant obtained from the obtained XRD chart and the temperature can be mentioned.

Examples of the solid electrolyte material include compounds represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1), and the general formula Li _{1 + x} Al _x Ti _2-x (PO ₄ ) _3. The compound is particularly limited as long as it is at least one of a compound represented by (0 ≦ x ≦ 1) and a compound represented by the general formula Li _x La _y TiO ₃ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1). For example, Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ can be preferably used. Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ has a volume expansion coefficient of 34.6% at 600 ° C., which is relatively low compared to a compound used as a general solid electrolyte material. This is because sintering proceeds. Therefore, it can suppress that an electrode active material and an unnecessary side reaction arise at the time of sintering.

  Moreover, as a volume ratio of the solid electrolyte material with respect to the sum total of a solid electrolyte material, an electrode active material, and a conductive support agent, it is preferable that it is 10 volume% or more, for example, it is more preferable that it is 30 volume% or more, and 35 volumes. It is particularly preferable that the content be in the range of% to 70% by volume.

Examples of the shape of the solid electrolyte material in the present invention include a particle shape, and among them, a true spherical shape or an elliptical spherical shape is preferable. In addition, when the solid electrolyte material has a particle shape, the average particle diameter is not particularly limited, but is preferably in the range of 50 nm to 5 μm, for example, in the range of 100 nm to 3 μm. Is more preferable. Here, the average particle size and is usually refers to the average particle diameter D ₅₀ was measured with a particle size distribution measurement, a value calculated by a scanning electron microscope (SEM) may be an average particle diameter. In the calculation by SEM, the longest diameter and the shortest diameter of particles (n ≧ 100) of the solid electrolyte material are measured, and the average value is obtained.

2. Electrode Active Material The electrode active material in the present invention includes a compound represented by the general formula Li ₃ M ¹ ₂ (PO ₄ ) ₃ (M ¹ is at least one of V, Fe and Ti) and a general formula LiM ² PO. ₄ (M ² is at least one of Ni, Co, and Fe).

The electrode active material does not react even when fired with the above-described solid electrolyte material, that is, does not generate a different phase. Since the heterogeneous phase is the same as that described in the section “1. Solid electrolyte material”, description thereof is omitted here. The mechanism by which the electrode active material does not produce a different phase from the above-described solid electrolyte material is not clear, but can be estimated as follows. That is, since the electrode active material has a phosphoric acid group (PO ₄ ), it is considered that the characteristic change hardly occurs at the time of sintering and does not cause a different phase from the above-described solid electrolyte material. Therefore, since ions can move well in the obtained electrode sintered body, an electrode sintered body having high ion conductivity can be obtained.

^{M 1} in the general formula _{^{Li 3 M 1 2 (PO 4}} ) 3 is, V, Fe, at least one of Ti, particularly preferably among them V.

In addition, the above M ¹ is the sum of the valences of M ^{1 in} the above general formula Li ₃ M ¹ ₂ (PO ₄ ) ₃ being 6 valences. That is, M ¹ in the above general formula may be the same element or a combination of different elements. Further, M ¹ in the above general formula may be a combination of elements having the same valence or may be a combination of elements having different valences. For example, V (III) can be given as a combination of trivalent elements.

Specific examples of the compound represented by the general formula Li ₃ M ¹ ₂ (PO ₄ ) ₃ include Li ₃ V ₂ (PO ₄ ) ₃ , Li ₃ Fe ₂ (PO ₄ ) ₃ , and Li ₃ Ti ₂ ( PO ₄ ) _{3 and the} like can be mentioned, among which Li ₃ V ₂ (PO ₄ ) ₃ can be preferably used.

In the general formula LiM ² PO ₄ , M ² is at least one of Ni, Co, and Fe. Specific examples of the compound represented by the general formula LiM ² PO ₄ include LiNiPO ₄ , LiCoPO ₄ , LiFePO _{4, and the} like.

  The electrode active material in the present invention is preferably a substance that undergoes a heating sintering process at a temperature at which the above-described solid electrolyte material is sintered. Here, the sintering process by heating is a series of processes in which surface diffusion first occurs on the particle surface, followed by evaporation and aggregation, followed by volume diffusion and interface (grain boundary) diffusion by heating. Say.

As a combination of the electrode active material and the solid electrolyte material in the present invention, for example, the electrode active material is Li ₃ V ₂ (PO ₄ ) ₃ (volume expansion coefficient at 600 ° C .: 9.5%), and the solid electrolyte material is Li _{A combination of 1.5} Al _0.5 Ge _1.5 (PO ₄ ) ₃ (volume expansion coefficient at 600 ° C .: 34.6%) can be preferably used. It is because generation | occurrence | production of the unnecessary side reaction of an electrode active material and a solid electrolyte material can be suppressed.

  In addition, the volume ratio of the electrode active material to the total of the solid electrolyte material, the electrode active material, and the conductive additive is, for example, preferably 20% by volume or more, more preferably 30% by volume or more, and 30% by volume. It is particularly preferable that the content be in the range of% to 50% by volume. This is because if the volume ratio of the electrode active material is less than the above range, the energy density may decrease. Therefore, sufficient performance may not be obtained when used in a battery. On the other hand, when the volume ratio of the electrode active material exceeds the above range, there is a possibility that the ion conduction path cannot be sufficiently secured.

  Examples of the shape of the electrode active material in the present invention include a particle shape, and among them, a true spherical shape or an elliptical spherical shape is preferable. Moreover, when an electrode active material is a particle shape, it is preferable that the average particle diameter exists in the range of 0.1 micrometer-50 micrometers, for example. In addition, the said average particle diameter can be calculated | required by the method similar to the said solid electrolyte material.

3. Conductive aid The conductive aid in the present invention is such that the volume ratio with respect to the total of the solid electrolyte material, the electrode active material and the conductive aid is in the range of 5 vol% to 10 vol%, and in particular 6 vol%. % To 9% by volume is preferable, and 7% to 8% by volume is more preferable. This is because if the volume ratio of the conductive additive is less than the above range, there is a possibility that sufficient electron conductivity cannot be imparted to the electrode sintered body of the present invention. On the other hand, if the volume ratio of the conductive additive exceeds the above range, the sintered density of the electrode sintered body of the present invention may not be sufficiently maintained.

  The conductive auxiliary agent is not particularly limited as long as it has predetermined conductivity, and examples thereof include carbon materials such as carbon particles and carbon fibers. Examples of the carbon particles include furnace black (FB), acetylene black (AB), ketjen black (KB), activated carbon, graphite, and the like. Of these, KB can be preferably used. The particle diameter (primary diameter) of the carbon particles is, for example, preferably in the range of 1 nm to 10 μm, and more preferably in the range of 3 nm to 50 μm. In addition, the said average particle diameter can be calculated | required by the method similar to the solid electrolyte material and electrode active material which were mentioned above. Moreover, the said carbon fiber is a fibrous carbon substance, for example, VGCF (vapor-grown carbon fiber) can be used suitably. The fiber diameter of the carbon fiber is, for example, preferably in the range of 10 nm to 10 μm, and more preferably in the range of 50 nm to 1 μm. Further, the fiber length of the carbon fiber is, for example, preferably in the range of 10 nm to 100 μm, and more preferably in the range of 1 μm to 50 μm. Furthermore, the aspect ratio (fiber length / fiber diameter) of the carbon fiber is preferably in the range of 1 to 200, for example, and preferably in the range of 3 to 50. In addition, the fiber diameter and fiber length in carbon fiber can be calculated | required by observation by SEM, for example.

  Here, when the conductive support agent used for this invention is FB, for example, the volume ratio of the conductive support agent with respect to the sum total of a solid electrolyte material, an electrode active material, and a conductive support agent shall be 8 volume% or more, for example. Is more preferable, and it is particularly preferably in the range of 8% by volume to 10% by volume.

  Moreover, when the conductive support agent used for this invention is VGCF, for example, the volume ratio of the conductive support agent with respect to the sum total of a solid electrolyte material, an electrode active material, and a conductive support agent is 5 volume%-7 volume% especially. It is particularly preferable that it is within the range.

4). Electrode sintered body The electrode sintered body of the present invention is not particularly limited as long as its electron conductivity is 1.0 × 10 ⁻⁴ S / cm or more, and may exhibit higher electron conductivity. preferable. For example, the electron conductivity at normal temperature (25 ° C.) is preferably 1.0 × 10 ⁻³ S / cm or more, and more preferably 1.0 × 10 ⁻² S / cm or more. In addition, as a measuring method of electronic conductivity, the method of measuring the direct current | flow resistance of a positive electrode sintered compact single-piece | unit and calculating using the volume of the sintered compact can be mentioned, for example.

  The electrode sintered body of the present invention is not particularly limited as long as it includes the above-described solid electrolyte material, electrode active material, and conductive aid, and only the solid electrolyte material, electrode active material, and conductive aid described above. It may be configured from the above, and may have a configuration other than the solid electrolyte material, the electrode active material, and the conductive additive, if necessary. For example, a binder or the like can be used. By adding a binder, flexibility can be imparted to the electrode sintered body. Examples of the binder include polyvinyl butyral (PVB) and an acrylic binder.

  Here, as described above, sintering generally refers to a phenomenon in which a solid powder aggregate is solidified and becomes dense. 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 can be determined by checking whether or not the sintered electrode sintered body has a density that cannot be reached by the compacting treatment.

  The sintered density in the electrode sintered body of the present invention is represented by the ratio of the actually measured density to the theoretical density (actually measured density / theoretical density × 100), and is preferably 70% or more, for example, 75% More preferably, it is more preferably 85% or more. This is because if the sintered density is too low, the amount of electrode active material per unit volume may be low, and battery performance may be reduced when a battery is produced. Here, the theoretical density refers to the true density of the powder material used as the raw material of the electrode sintered body. As a method for measuring the true density, a known method can be used. Examples of the method for measuring the measured density of the electrode sintered body include a method of calculating by calculating the weight and volume of the electrode sintered body and dividing the weight of the electrode sintered body by the volume. .

  The electrode sintered body of the present invention may be in the form of a pellet or a sheet. Moreover, the shape of an electrode sintered compact can use the shape similar to the existing various sintered compact, for example, column shape, flat plate shape, cylindrical shape etc. can be mentioned. The thickness of the electrode sintered body is appropriately set according to the shape of the electrode sintered body described above, and is preferably in the range of 10 μm to 50 μm, for example.

  The electrode sintered body can be used as, for example, a positive electrode active material layer or a negative electrode active material layer of a battery. Further, in the present invention, the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer are power generation element sintered bodies laminated in this order, and at least one of the positive electrode active material layer and the negative electrode active material layer is the above-mentioned. It is also possible to provide a power generation element sintered body that is an electrode sintered body.

  Here, there is no clear distinction between the positive electrode active material and the negative electrode active material, and the charge / discharge potentials and oxidation-reduction potentials of the two types of compounds are compared. A battery having an arbitrary voltage can be configured by combining those having a base potential as the negative electrode active material. Therefore, the electrode active material described above may function as a positive electrode active material or may function as a negative electrode active material.

  When producing a battery using the electrode sintered body of the present invention as a positive electrode active material layer, the electrolyte layer in the battery is not particularly limited as long as it has at least an electrolyte material, and the form of the electrolyte layer is Examples thereof include a liquid electrolyte layer, a gel electrolyte layer, a polymer electrolyte layer, and a solid electrolyte layer.

  The solid electrolyte layer has at least a solid electrolyte material, and the solid electrolyte material in the solid electrolyte layer may be the same as that described in the above “1. Solid electrolyte material”. An electrolyte material may be used. The content of the solid electrolyte material in the solid electrolyte layer is, for example, preferably 60% by weight or more, particularly 70% by weight or more, and particularly preferably 80% by weight or more. The solid electrolyte layer may be composed of only a solid electrolyte material, and may have a binder as necessary. In addition, the thing similar to the said electrode sintered compact can be used for a binder.

  The thickness of the electrolyte layer varies greatly depending on the type of the electrolyte material and the configuration of the battery, but is preferably in the range of 2 μm to 1000 μm, for example.

  When producing a battery using the electrode sintered body of the present invention as a positive electrode active material layer, the negative electrode active material layer in the battery is a layer containing at least a negative electrode active material, and if necessary, a solid electrolyte material, It may further contain at least one of a conductive additive and a binder.

Although the said negative electrode active material is not specifically limited, For example, a carbon active material, a metal active material, an oxide active material etc. can be mentioned. Examples of the carbon active material include graphite such as mesocarbon microbeads (MCMB) and highly oriented graphite (HOPG), and amorphous carbon such as hard carbon and soft carbon. Examples of the metal active material include lithium metal (Li), a lithium alloy (LiM, and examples of M include Sn, Si, Al, Ge, Sb, and P), and a lithium-storable intermetallic compound (MgxM (Examples of M include Sn, Ge, and Sb.) In addition, examples of the oxide active material include Nb ₂ O ₅ , Li ₄ Ti ₅ O ₁₂ , and SiO. Can be mentioned.

  Examples of the shape of the negative electrode active material include a particle shape and a film shape. The average particle size of the particle-shaped negative electrode active material is preferably in the range of, for example, 0.1 μm to 50 μm. The method for obtaining the average particle diameter is as described above. Further, the content of the negative electrode active material in the negative electrode active material layer is preferably in the range of 10 wt% to 99 wt%, for example, and more preferably in the range of 20 wt% to 90 wt%.

  The negative electrode active material layer preferably contains a solid electrolyte material. This is because the ion conductivity in the negative electrode active material layer can be improved. The solid electrolyte material contained in the negative electrode active material layer may be the solid electrolyte material described in “1. Solid electrolyte material” above, or may be another general solid electrolyte material. The content of the solid electrolyte material in the negative electrode active material layer is, for example, preferably in the range of 1% by weight to 90% by weight, and more preferably in the range of 10% by weight to 80% by weight.

  The negative electrode active material layer may contain a conductive additive. In addition, as a conductive support agent, what was described in the item of the above-mentioned "3. conductive support agent" can be used. The negative electrode active material layer may further contain a binder. In addition, as a binder, the thing similar to the positive electrode active material layer mentioned above can be used. Moreover, the thickness of the negative electrode active material layer can be appropriately set according to the shape or the like of the target all-solid battery, but is preferably in the range of 10 μm to 100 μm, for example.

  Examples of the type of battery using the electrode sintered body of the present invention include a lithium battery, a sodium battery, a magnesium battery, and a calcium battery, and among them, a lithium battery is preferable. The battery may be a primary battery or a secondary battery, but is preferably a secondary battery. This is because it can be repeatedly charged and discharged and is useful, for example, as a vehicle-mounted battery. Examples of the shape of the battery include a coin shape, a laminate shape, a cylindrical shape, and a square shape.

  Here, in the case of producing a battery using the electrode sintered body of the present invention, it has a member used for a general battery, for example, a positive electrode current collector that collects a positive electrode active material layer, and A negative electrode current collector that collects current from the negative electrode active material layer can be given. Examples of materials for the positive electrode current collector and the negative electrode current collector include gold, silver, palladium, copper, and nickel. The thickness, shape, and the like of the positive electrode current collector and the negative electrode current collector are preferably appropriately selected according to the use of the battery. Moreover, a general battery case can be used for the battery case used for the said battery.

B. Next, a method for manufacturing an electrode sintered body according to the present invention will be described. The method for producing an electrode sintered body according to the present invention includes a preparation step of obtaining a sintered body forming material by mixing a solid electrolyte material, an electrode active material and a conductive additive, and sintering the sintered body forming material. The solid electrolyte material is represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1). compounds of the general formula _{Li 1 + x Al x Ti 2} -x (PO 4) 3 (0 ≦ x ≦ 1) compound represented by the general formula _{Li x La y TiO 3 (0} ≦ x ≦ 1,0 ≦ y ≦ 1), and the electrode active material is represented by the general formula Li ₃ M ¹ ₂ (PO ₄ ) ₃ (M ¹ is at least one of V, Fe, and Ti). the compounds and the general formula ^{LiM 2} _PO 4 ^(M 2 is Ni, Co, less of Fe Is also at least one compound, and the volume ratio of the conductive assistant to the total of the solid electrolyte material, the electrode active material and the conductive assistant is 5% by volume to 10%. It is in the range of volume%, and the electron conductivity of the electrode sintered body after the sintering step is 1.0 × 10 ⁻⁴ S / cm or more.

  FIG. 2 is an explanatory view showing an example of a method for producing an electrode sintered body according to the present invention. As shown in FIG. 2, for example, an electrode active material 1, a solid electrolyte material 2, and a conductive additive 3 are prepared and mixed by mortar treatment to obtain a sintered body forming material (FIG. 2 (a)). Next, the obtained sintered compact forming material is compacted by, for example, a uniaxial heating molding method (FIG. 2B) to form a compact 4 (FIG. 2C). The obtained green compact 4 is further pressurized by, for example, a cold isostatic pressing (CIP) method (FIG. 2 (d)). Thereafter, the green compact 4 that is the material for forming a sintered body is fired (FIG. 2E). Thereby, the electrode sintered body 10 is obtained (FIG. 2F).

According to the present invention, along with the above-described solid electrolyte material and electrode active material, by mixing a conductive additive so as to satisfy a predetermined volume ratio, high electron conductivity can be achieved while sufficiently maintaining the sintered density. The electrode sintered body shown can be obtained.
Hereinafter, each process of the present invention will be described in detail.

1. Preparation Step The preparation step in the present invention is a step of obtaining a sintered body forming material by mixing a solid electrolyte material, an electrode active material, and a conductive additive. Here, since the solid electrolyte material, the electrode active material, and the conductive additive are the same as the contents described in the above “A. Electrode sintered body”, description thereof is omitted here.

  The sintered body forming material obtained in this step is not particularly limited as long as the solid electrolyte material, the electrode active material, and the conductive additive are sufficiently mixed and dispersed. Examples of the method include a mortar mixing method.

  The sintered body forming material is formed into a desired shape before the firing step described later. Examples of the molding method include a powder molding method such as a uniaxial pressure molding method. In addition, the obtained green compact may be further pressurized by, for example, a cold isostatic pressing (CIP) method or the like. The density of the green compact thus obtained is represented by the ratio of the measured density to the theoretical density (measured density / theoretical density × 100), and is preferably 50% or more, for example, 55% More preferably, it is in the range of -75%. The theoretical density is the same as that described in the section “A. Electrode sintered body”. Examples of the method for measuring the actual density of the green compact include, for example, a method of calculating the weight and volume of the obtained green compact and dividing the weight of the green compact by the volume. it can.

2. Next, the firing process in the present invention will be described. The firing step in the present invention is a step of firing the above-described sintered body forming material.

  The temperature at the time of firing in this step is not particularly limited, but it may be a temperature that is equal to or higher than the temperature at which the solid electrolyte material contained in the sintered body forming material proceeds. Depending on the type of the solid electrolyte material, etc., it can be set as appropriate. In addition, at the above temperature, the electrode active material is preferably a material that undergoes a sintering process by heating. The sintering process by heating is the same as that described in the section “A. Electrode Sintered Body”, and the description is omitted here.

Specifically, the firing temperature in this step is preferably 550 ° C. or higher, more preferably in the range of 550 ° C. to 1000 ° C., and in the range of 580 ° C. to 600 ° C. Further preferred. In particular, when the solid electrolyte material is Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ , the firing temperature is preferably 550 ° C. or higher, and a range of 550 ° C. to 650 ° C. It is more preferable that it is within the range of 580 ° C to 600 ° C.

  Here, as described above, sintering generally refers to a phenomenon in which a solid powder aggregate is solidified and becomes dense. 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 can be determined by checking whether or not the sintered electrode sintered body has a density that cannot be reached by the compacting treatment.

  In the electrode sintered body obtained by the present invention, the density of the solid electrolyte material and the electrode active material, that is, the sintered density, is the same as the content described in the above section “A. Electrode sintered body”. Therefore, the description here is omitted.

  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.

  The present invention will be described more specifically with reference to the following examples.

[Example 1-1]
(Preparation of sintered body forming material)
Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (manufactured by Kojundo Chemical Laboratory Co., Ltd., average particle size: 9.03 μm, LAGP) was prepared as a solid electrolyte material. In addition, Li ₃ V ₂ (PO ₄ ) ₃ (manufactured by Kojundo Chemical Laboratory Co., Ltd., average particle size 8.0 μm, LVP) was prepared as an electrode active material. Furthermore, furnace black was prepared as a conductive assistant. Next, LAGP, LVP, and FB were mixed and dispersed by a mortar treatment at a volume ratio of LAGP: LVP: FB = 65: 30: 5 to obtain a sintered body forming material. Further, 0.25 g of a sintered body forming material was pressed to produce a pellet (φ = 13.0) green compact.

(Production of electrode sintered body)
The green compact formed into a pellet was fired at 600 ° C. under a nitrogen atmosphere for 2 hours to obtain an electrode sintered body.

[Examples 1-2 to 1-3]
An electrode sintered body was obtained in the same manner as in Example 1-1 except that LAGP, LVP, and FB were changed to the volume ratios shown in Table 1, respectively.

[Comparative Examples 1-1 to 1-7]
An electrode sintered body was obtained in the same manner as in Example 1-1 except that LAGP, LVP, and FB were changed to the volume ratios shown in Table 1, respectively.

[Example 2-1]
Except that the vapor-grown carbon fiber (manufactured by Showa Denko KK, VGCF) was obtained as a conductive auxiliary agent, respectively, with a volume ratio of LAGP: LVP: VGCF = 65: 30: 5, to obtain a sintered body forming material, An electrode sintered body was obtained in the same manner as Example 1-1.

[Example 2-2]
An electrode sintered body was obtained in the same manner as in Example 2-1, except that LAGP, LVP, and VGCF were set to the volume ratios shown in Table 2, respectively.

[Comparative Examples 2-1 to 2-2]
An electrode sintered body was obtained in the same manner as in Example 2-1, except that LAGP, LVP, and VGCF were set to the volume ratios shown in Table 2, respectively.

[Reference Example 1]
An electrode sintered body was obtained in the same manner as in Example 1-1 (conductive auxiliary agent: 8% by volume) except that the firing temperature was 750 ° C.

[Evaluation 1]
(Density measurement)
The densities of the electrode sintered bodies obtained in Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-7 were measured. The results are shown in Table 1 and FIG. Moreover, the density of the electrode sintered compact obtained in Examples 2-1 to 2-2 and Comparative Examples 2-1 to 2-2 was measured. The results are shown in Table 2 and FIG.

(Electron conductivity measurement)
The electron conductivity of the electrode sintered bodies obtained in Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-7 was measured. The results are shown in Table 1 and FIG. Moreover, the electronic conductivity of the electrode sintered body obtained in Examples 2-1 to 2-2 and Comparative Examples 2-1 to 2-2 was measured. The results are shown in Table 2 and FIG.

  As shown in Table 1 and FIG. 4, when the conductive auxiliary agent is FB, the volume ratio of the conductive auxiliary agent to the total of the solid electrolyte material, the electrode active material and the conductive auxiliary agent is 5% by volume to 10% by volume. It can be confirmed that high electronic conductivity is exhibited while maintaining the sintered density to be 70% or more by mixing within the range, particularly within the range of 8% by volume to 10% by volume.

  Further, as shown in Table 2 and FIG. 5, when the conductive auxiliary agent is VGCF, the volume ratio of the conductive auxiliary agent to the total of the solid electrolyte material, the electrode active material and the conductive auxiliary agent is 5% by volume to 10% by volume. By mixing so as to be in the range of 5 vol% to 7 vol%, it can be confirmed that high electron conductivity is exhibited while maintaining the sintered density to be 70% or more.

(Production of evaluation battery)
Using the electrode sintered bodies obtained in Examples 1-1 and 1-3, Comparative Example 1-1, and Reference Example 1, an evaluation battery 20 as shown in FIG. 3 was produced. The obtained electrode sintered body 10 was used as a working electrode (positive electrode 11), and Li metal was used as a counter electrode (negative electrode 13). Further, as the electrolyte layer 13, a supporting salt (LiClO ₄ , manufactured by Kanto Denka), a non-aqueous solvent (ethyl carbonate (EC): diethyl carbonate (DEC) = 1: 1 mixed solvent, EC and DEC are manufactured by Kanto Denka) The evaluation battery 20 was obtained using a support salt concentration of 1 mol / L in a non-aqueous solvent and gel (PMMA) (see FIG. 3). In addition, as the washer 15, the spacer 16, the positive electrode can 14, the negative electrode can 17, and the packing 18, a general thing can be used.

[Evaluation 2]
The obtained battery for evaluation was evaluated under the conditions of an environmental temperature of 25 ° C. and a voltage scanning range of 2.0 V to 4.6 V. The current rate in Example 1-1 (FIG. 6), 1-3 (FIG. 7) and Reference Example 1 (FIG. 9) is 0.1 C, and the current rate in Comparative Example 1-1 (FIG. 8) is 0.02C. The results are shown in Table 3 and FIGS.

  From Table 3 and FIGS. 6-8, in Examples 1-1 and 1-3, high discharge capacity and charging / discharging efficiency can be confirmed. This is because an electrode sintered body exhibiting high electron conductivity can be obtained while maintaining the sintered density by mixing FB at a predetermined volume ratio. On the other hand, in Comparative Example 1-1, since the conductive auxiliary agent is not added, the electron conductivity is not imparted, so that it is considered that the discharge capacity and the charge / discharge efficiency are lower than those of Example 1-1 and the like. Moreover, when Examples 1-1 and 1-3 are compared, it can be confirmed that in Example 1-3 in which the volume ratio of the conductive additive is large, the discharge capacity and the charge / discharge efficiency are lower than in Example 1-1. This is presumably because it was difficult to secure an ion conduction path due to an increase in the amount of the conductive additive added.

  Moreover, when Example 1-1 and Reference Example 1 are compared from the results of Table 3 and FIGS. 6 and 9, in Reference Example 1 where the firing temperature is higher than 750 ° C., Example 1 in which the firing temperature is 600 ° C. It can be confirmed that the discharge capacity and the charge / discharge efficiency are low compared to -1. This is presumably because the firing temperature in Reference Example 1 was higher and a side reaction between the solid electrolyte material and the electrode active material occurred during firing.

[Reference Example 2]
As in Example 1-1, Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ (manufactured by Kojundo Chemical Laboratory Co., Ltd., average particle size 9.03 μm, LAGP) was used as the solid electrolyte material. As an electrode active material, Li ₃ V ₂ (PO ₄ ) ₃ (manufactured by Kojundo Chemical Laboratory Co., Ltd., average particle size 8.0 μm, LVP) was prepared. After LAGP and LVP were mixed to obtain a material for forming a sintered material, a pellet-shaped green compact was produced. The pellet-shaped green compact was fired at 600 ° C. to obtain a sintered body.

[Reference Examples 3 to 4]
A sintered body was obtained in the same manner as in Reference Example 2 except that LATP and LLTO were used as the solid electrolyte material and fired at 1000 ° C.

[Evaluation]
The sintered bodies obtained in Reference Examples 2 to 4 were pulverized in a mortar and subjected to X-ray diffraction (XRD) measurement. For XRD measurement, RIG Ultimate III made by Rigaku was used, and CuKα rays were used. In the XRD measurement results of Reference Examples 2 to 4, it was confirmed that peaks of components other than the solid electrolyte material and the electrode active material were not detected. For this reason, it was confirmed that when a sintered body was produced using LAGP, LATP, and LLTO as the solid electrolyte material and LVP as the electrode active material, no heterogeneous phase was produced.

DESCRIPTION OF SYMBOLS 1 ... Electrode active material 2 ... Solid electrolyte material 3 ... Conductive auxiliary agent 4 ... Powder compact 10 ... Electrode sintered body 11 ... Positive electrode active material layer 12 ... Electrolyte layer 13 ... Negative electrode active material layer 14 ... Positive electrode collector (positive electrode) can)
15 ... Washer 16 ... Spacer 17 ... Negative electrode current collector (negative electrode can)
18 ... Packing 20 ... Battery for evaluation

Claims (2)

An electrode sintered body including a solid electrolyte material, an electrode active material, and a conductive additive,
The solid electrolyte material is a compound represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1), the general formula Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ ( 0 ≦ x ≦ 1) and at least one compound represented by the general formula Li _x La _y TiO ₃ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1),
The electrode active material is represented by the general formula ^{_{Li 3 M 1 2 (PO 4}} ) 3 (M 1 is V, Fe, at least one of Ti) and a compound represented by general formula ^{LiM 2} _PO 4 ^(M 2 is At least one of Ni, Co, and Fe).
The volume ratio of the conductive aid to the total of the solid electrolyte material, the electrode active material and the conductive aid is in the range of 5 vol% to 10 vol%,
The electrode sintered body has an electron conductivity of 1.0 × 10 ⁻⁴ S / cm or more. A preparation step of obtaining a sintered body forming material by mixing a solid electrolyte material, an electrode active material and a conductive additive;
A sintering step of sintering the sintered body forming material, and a method of manufacturing an electrode sintered body comprising:
The solid electrolyte material is a compound represented by the general formula Li _{1 + x} Al _x Ge _2-x (PO ₄ ) ₃ (0 ≦ x ≦ 1), the general formula Li _{1 + x} Al _x Ti _2-x (PO ₄ ) ₃ ( 0 ≦ x ≦ 1) and at least one compound represented by the general formula Li _x La _y TiO ₃ (0 ≦ x ≦ 1, 0 ≦ y ≦ 1),
The electrode active material is represented by the general formula ^{_{Li 3 M 1 2 (PO 4}} ) 3 (M 1 is V, Fe, at least one of Ti) and a compound represented by the general formula ^{LiM 2} _PO 4 ^(M 2 is At least one of Ni, Co, and Fe).
The volume ratio of the conductive aid to the total of the solid electrolyte material, the electrode active material and the conductive aid is in the range of 5 vol% to 10 vol%,
The electrode sintered body after the sintering step has an electron conductivity of 1.0 × 10 ⁻⁴ S / cm or more.

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