JP2014154267A - All-solid battery, and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique which enables the reduction in internal resistance of an all-solid battery.SOLUTION: An all-solid battery comprises: a positive electrode layer including a positive electrode active material; a negative electrode layer including a negative electrode active material; and a solid electrolytic layer located between the positive and negative electrode layers. The solid electrolytic layer is formed by an oxide-based solid electrolytic material. The negative electrode layer includes a lithium-aluminum alloy as the negative electrode active material, and a sulfide-based solid electrolytic material. Of particles of the lithium-aluminum alloy included in the negative electrode layer, particles of a mass ratio of 95% or larger have a particle diameter of 100 μm or smaller.

Description

  The present invention relates to an all-solid battery and an all-solid battery manufacturing method.

  Conventionally, as a technique related to an electrode used in an all solid state battery, for example, those disclosed in Patent Documents 1 and 2 are known. Patent Document 1 describes that a lithium-aluminum alloy plate is used as a negative electrode of an all-solid battery. Patent Document 2 describes using a press body formed by mixing and press-molding a lithium-aluminum alloy powder and a solid electrolyte powder as a negative electrode of an all-solid battery.

JP 2007-324079 A JP-A-8-148180 Japanese Patent Laid-Open No. 1-109662 Japanese Patent Laid-Open No. 1-186556

  However, the techniques described in Patent Documents 1 and 2 have a problem that sufficient studies have not been made to reduce the internal resistance of all-solid-state batteries.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

(1) According to one aspect of the present invention, an all-solid battery is provided. The all-solid battery includes a positive electrode layer containing a positive electrode active material; a negative electrode layer containing a negative electrode active material; and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer; The solid electrolyte layer is formed of an oxide-based solid electrolyte material; the negative electrode layer includes a lithium-aluminum alloy as the negative electrode active material, and further includes a sulfide-based solid electrolyte material. The particle diameter of 95% or more of the lithium-aluminum alloy particles contained in the negative electrode layer is 100 μm or less. According to this form of the all-solid-state battery, when the negative electrode layer is formed by press-molding the sulfide-based solid electrolyte material and the lithium-aluminum alloy particles, cracks are generated in the lithium-aluminum alloy particles. The internal resistance of the all-solid battery can be reduced.

(2) In the all solid state battery of the above aspect, the negative electrode layer may have a bulk density of 1.30 g / cm ³ or more. According to this form of the all-solid-state battery, the number of voids existing in the negative electrode layer is reduced, and the interface between the lithium-aluminum alloy particles and the sulfide-based solid electrolyte is sufficiently bonded. The resistance can be further reduced.

(3) According to another aspect of the present invention, a method for producing an all-solid battery is provided. This method for producing an all-solid-state battery is a method comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer located between the positive electrode layer and the negative electrode layer; A step of forming a positive electrode layer by containing a substance; (b) a step of forming the negative electrode layer by containing a negative electrode active material; and (c) the solid electrolyte using an oxide-based solid electrolyte material The step (b) uses a lithium-aluminum alloy as the negative electrode active material, and further contains a sulfide-based solid electrolyte material in the negative electrode layer. The particle diameter of 95% or more of the lithium-aluminum alloy particles contained in the negative electrode layer in the step (b) is 100 μm or less.

  The present invention can also be realized in various forms other than an all-solid battery and an all-solid battery manufacturing method. For example, it can be realized in the form of a mobile body such as an automobile equipped with an all-solid battery, an electronic device equipped with an all-solid battery, and the like.

It is explanatory drawing which shows the cross section of the all-solid-state battery as one Embodiment of this invention. It is an image which shows the result of surface observation of negative electrode layer sample A1. It is an image which shows the result of surface observation of negative electrode layer sample A2. It is an image which expands and shows the result of surface observation of negative electrode layer sample A2. It is an image which shows the result of surface observation of negative electrode layer sample A3. It is an image which shows the result of surface observation of negative electrode layer sample A5. It is explanatory drawing which shows the experimental result regarding the particle diameter of Li-Al alloy powder in a tabular form. It is explanatory drawing which shows the relationship between the applied pressure at the time of press molding of a negative electrode layer, and the bulk density of a negative electrode layer in a graph format. It is explanatory drawing which shows the relationship between the bulk density of a negative electrode layer, and the internal resistance of an all-solid-state battery in a graph format. It is explanatory drawing which put together the experimental result regarding the bulk density of a negative electrode layer in tabular form.

Next, embodiments of the present invention will be described in the following order based on the embodiments.
A. Embodiment:
B. Experimental example on particle diameter of Li-Al alloy powder:
C. Experimental example on bulk density of negative electrode layer:
D. Variations:

A. Embodiment:
A-1: Configuration of all solid state battery:
FIG. 1 is an explanatory view showing a cross section of an all solid state battery 10 as one embodiment of the present invention. The all-solid-state battery 10 includes a battery body 15 and a pair of current collectors 50 and 60 that sandwich the battery body 15 from both sides. The battery body 15 includes a positive electrode layer 20 that functions as a positive electrode, a negative electrode layer 30 that functions as a negative electrode, and a conductive solid electrolyte layer 40 positioned between the positive electrode layer 20 and the negative electrode layer 30.

  The current collectors 50 and 60 are conductive plate-like members, and are formed of stainless steel (SUS) in this embodiment. However, the current collectors 50 and 60 may be formed of other conductive members. For example, the current collectors 50 and 60 are made of a conductive metal material selected from nickel (Ni), titanium (Ti), iron (Fe), copper (Cu), aluminum (Al), and alloys thereof, carbon It may be formed of a material or the like.

A-2. Detailed configuration of the positive electrode layer:
The positive electrode layer 20 is formed by press molding a material containing a positive electrode active material, a sulfide-based solid electrolyte, and conductive carbon. In the present embodiment, the positive electrode layer 20 contains sulfur as a positive electrode active material, and a sulfide-based lithium ion conductive solid electrolyte as a sulfide-based solid electrolyte.

However, the positive electrode layer 20 may contain another substance instead of sulfur as a positive electrode active material. For example, the positive electrode layer 20 may contain Li ₄ Ti ₅ O ₁₂ (hereinafter also referred to as “LTO”) instead of sulfur as a positive electrode active material. Further, the positive electrode layer 20 may contain other sulfide-based solid electrolyte instead of the sulfide-based lithium ion conductive solid electrolyte. The positive electrode layer 20 may not contain at least one of a sulfide-based solid electrolyte and conductive carbon.

Examples of the sulfide-based lithium ion conductive solid electrolyte include a Li ₂ S—P ₂ S ₅ system, a LiI—Li ₂ S—P ₂ S ₅ system, a LiI—Li ₂ S—B ₂ S ₃ system, and a LiI. A solid electrolyte selected from -Li ₂ S-SiS ₂ -based solid electrolyte, thiolithicone, Li ₁₀ GeP ₂ S _{12 and the} like can be used. Here, as the Li ₂ S—P ₂ S ₅ based solid electrolyte, it is preferable to use a solid electrolyte represented by the following formula (1).
_{XLi 2 S- (1-X)} P 2 S 5 ... (1)
(In the formula, X is 0.65 ≦ X ≦ 0.80.)

The sulfide-based lithium ion conductive solid electrolyte preferably has high ionic conductivity. Specifically, the ionic conductivity of the sulfide-based lithium ion conductive solid electrolyte is preferably 10 ⁻⁵ S / cm or more, and more preferably 10 ⁻⁴ S / cm or more.

  Further, it is desirable that the sulfide-based lithium ion conductive solid electrolyte is sufficiently soft, that is, has a small Young's modulus. Specifically, the Young's modulus of the sulfide-based lithium ion conductive solid electrolyte is preferably 0.08 to 30 GPa, and more preferably 0.08 to 20 GPa.

  In order to include the ionic conductivity and Young's modulus of the sulfide-based lithium ion conductive solid electrolyte membrane within the above preferable range, X in the above formula (1) is set to 0.65 ≦ X ≦ 0.80. A value within the range may be used. However, X in the above formula (1) may be a value outside the above range.

  As the conductive carbon, for example, ketjen black, acetylene black (for example, Denka Black, Denka Black is a registered trademark), and furnace black (for example, Vulcan manufactured by Cabot Corporation) can be used.

  Moreover, it is preferable that the particle diameter of electroconductive carbon is small. This is because the volume resistivity of the positive electrode layer 20 can be sufficiently reduced while the electron conductivity in the positive electrode layer 20 is sufficiently ensured as the particle diameter of the conductive carbon is small. Therefore, it is preferable to use ketjen black or acetylene black as the conductive carbon.

A-3. Detailed configuration of the negative electrode layer:
The negative electrode layer 30 is formed by press molding a material containing a negative electrode active material and a sulfide solid electrolyte. In this embodiment, the negative electrode layer 30 contains a lithium-aluminum alloy (Li-Al alloy) as a negative electrode active material, and contains a sulfide-based lithium ion conductive solid electrolyte as a sulfide-based solid electrolyte. doing. However, the negative electrode layer 30 may contain another sulfide-based solid electrolyte instead of the sulfide-based lithium ion conductive solid electrolyte.

  When a sulfide-based solid electrolyte that is deformed by pressurization is mixed with a Li-Al alloy that is a metal material having a relatively large Young's modulus (relatively hard) as in this embodiment, the sulfide-based solid electrolyte is obtained. In addition to functioning as a binder for press-molding the negative electrode layer 30, it also functions as a binder for press-bonding the negative electrode layer 30 and the solid electrolyte layer 40, thereby improving the performance of the all-solid battery 10. Can do. The sulfide-based solid electrolyte also functions as an ion conduction aid in the negative electrode layer 30 and can improve the performance of the all-solid battery 10.

  Furthermore, in this embodiment, among the particles of the Li—Al alloy contained in the negative electrode layer 30, the particle size of particles having a mass ratio of 95% or more is 100 μm or less. If it does in this way, generation | occurrence | production of the crack in the particle | grains of a Li-Al alloy can be suppressed at the time of press molding. As a result, the internal resistance of the all solid state battery 10 can be reduced.

  The reason why cracking can be suppressed is that the smaller the particle diameter, the larger the surface area of the Li-Al alloy particles in the same volume, so the contact area with the sulfide-based solid electrolyte during press molding is increased. This is because the pressure applied to the Li—Al alloy particles during press molding is dispersed. The basis for setting the particle diameter of the Li—Al alloy particles to 100 μm or less will be described later.

Furthermore, in this embodiment, the bulk density of the negative electrode layer 30 is 1.30 g / cm ³ or more. By doing so, the number of vacancies present in the negative electrode layer 30 is reduced, and the interface between the Li—Al alloy particles and the sulfide-based solid electrolyte is sufficiently joined, so that the internal resistance of the all-solid battery is further increased. Can be reduced. The basis for setting the bulk density of the negative electrode layer 30 to 1.30 g / cm ³ or more will be described later.

A-4: Detailed configuration of the solid electrolyte layer:
The solid electrolyte layer 40 is a plate member formed of an oxide-based solid electrolyte material. In the present embodiment, the solid electrolyte layer 40 is formed of an oxide-based lithium ion conductive solid electrolyte material. However, the solid electrolyte layer 40 may be formed of another oxide solid electrolyte material instead of the oxide lithium ion conductive solid electrolyte.

As the oxide-based lithium ion conductive solid electrolyte, for example, a phosphoric acid compound having a NASICON structure represented by the following formula (2) or a substituted product obtained by substituting a part thereof with another element, Li ₇ La ₃ It has a perovskite structure or a perovskite-like structure, such as a lithium ion conductor having a garnet-type structure or a garnet-type-like structure such as a Zr ₂ O _12- type lithium ion conductor, or a Li-La-Ti—O-type lithium ion conductor. A lithium ion conductor or the like can be used.
Li _{1 + Y} Al _Y M _2-Y (PO ₄ ) ₃ (2)
(In the formula, M is at least one selected from the group consisting of germanium, titanium, hafnium, and zirconium, and Y is 0 ≦ Y ≦ 1)

Among the above oxide-based lithium ion conductive solid electrolytes, a solid electrolyte in which M in Formula (2) is at least one selected from germanium and titanium is particularly excellent in lithium ion conductivity. Further, among the above oxide-based lithium ion conductive solid electrolytes, the solid electrolyte in which M in formula (2) is at least one selected from germanium, hafnium and zirconium has a relatively low reducibility, Reaction with the component contained in the electrode layer can be suppressed. For this reason, it is preferable to use a solid electrolyte in which M in the formula (2) is germanium as the oxide-based lithium ion conductive solid electrolyte. Among solid electrolytes in which M in the formula (2) is germanium, it is particularly preferable to use a solid electrolyte in which Y in the formula (2) is 0.5, that is, Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) _3. preferable.

  The solid electrolyte layer 40 is preferably dense. Specifically, the relative density with respect to the theoretical density of the solid electrolyte layer 40 is preferably 80% or more, and more preferably 90% or more. Here, the relative density can be obtained using the Archimedes method. By setting the relative density to 80% or more, the internal resistance of the all-solid battery 10 can be easily reduced.

  The solid electrolyte layer 40 is preferably a sintered body. Thereby, the density of the solid electrolyte layer 40 can be improved more easily, and the above relative density can be easily realized. The solid electrolyte layer 40 which is a sintered body can be produced by, for example, a solid phase reaction method. The solid phase reaction method is a method in which powder raw materials such as oxides, carbonates, and nitrates are weighed and mixed so as to have a desired composition and then fired.

Further, the solid electrolyte layer 40 preferably has an ionic conductivity of 10 ⁻⁵ S / cm or more, and more preferably 10 ⁻⁴ S / cm or more. In this way, the internal resistance of the all solid state battery 10 can be reduced.

  If the solid electrolyte layer 40 is formed of an oxide-based solid electrolyte as in this embodiment, the amount of sulfide-based solid electrolyte that can react with moisture and generate hydrogen sulfide in the all-solid battery 10 is reduced. Can be reduced. For this reason, the safety | security at the time of manufacture and use of the all-solid-state battery 10 can be improved.

B. Experimental example on particle diameter of Li-Al alloy powder:
B-1. Overview:
In this experimental example, in order to investigate the relationship between the particle diameter of the Li—Al alloy powder contained in the negative electrode layer 30 and the internal resistance of the all-solid battery 10, a plurality of negative electrodes having different particle diameters of the Li—Al alloy powder are used. While producing the sample of the electrode layer 30, the internal resistance of the all-solid-state battery 10 was investigated. In addition, the particle diameter of the Li—Al alloy powder and the presence or absence of cracks in the Li—Al alloy powder particles after press molding were also examined.

B-2. Sample preparation:
[Preparation of negative electrode layer]
In a glove box with an argon atmosphere and a dew point of −80 ° C., a mass ratio of Li—Al alloy powder and 75Li ₂ S-25P ₂ S ₅ glass as a sulfide-based lithium ion conductive solid electrolyte is 1: 1. Weighed so that a solvent was added and mixed using a planetary ball mill to prepare a Li-Al composite material. In this experimental example, a plurality of types of raw material powders having different particle diameters were prepared in order to produce a plurality of types of Li—Al composite materials having different particle diameters of the Li—Al alloy powder particles. And the following 5 types of Li-Al compound materials were produced.
Li-Al composite material 1: 95% or more (mass ratio) of particles of Li-Al alloy powder having a particle diameter of 300 μm or less and greater than 200 μm Li-Al composite material 2: 95% or more of Li-Al alloy powder (Mass ratio) particles having a particle size of 200 μm or less and greater than 100 μm Li—Al composite material 3: 95% or more (mass ratio) of particles of the Li—Al alloy powder have a particle size of 100 μm or less and 30 μm Larger Li—Al composite material 4: 95% or more (mass ratio) of the particles of the Li—Al alloy powder has a particle size of 30 μm or less and larger than 15 μm Li—Al composite material 5: 95 of the Li—Al alloy powder % Or more (mass ratio) particle diameter is 15 μm or less

The prepared Li—Al composite material (15 mg) was uniformly arranged on a SUS substrate, and press-molded at a pressure of 180 MPa to prepare samples of the following five types of negative electrode layers 30 (negative electrode pellets). .
Negative electrode layer sample A1: Li—Al composite material 1 (particle diameter of 300 μm or less)
Negative electrode layer sample A2: Li—Al composite material 2 (particle diameter of 200 μm or less)
Negative electrode layer sample A3: Li—Al composite material 3 (particle diameter of 100 μm or less)
Negative electrode layer sample A4: Li—Al composite material 4 (particle diameter of 30 μm or less)
Negative electrode layer sample A5: Li—Al composite material 5 (particle diameter of 15 μm or less)

[Preparation of positive electrode layer 1 (when using LTO composite)]
The mass ratio of Li ₄ Ti ₅ O ₁₂ as the positive electrode active material, 75Li ₂ S-25P ₂ S ₅ glass as the sulfide-based lithium ion conductive solid electrolyte, and ketjen black is 7: 3: 1. The mixture was weighed as described above and mixed at 230 rpm for 1 hour using a planetary ball mill to prepare an LTO composite material.

  The prepared LTO composite material (15 mg) was uniformly placed on a SUS substrate, and was press-molded at a pressure of 180 MPa to prepare a positive electrode layer 20 (positive electrode pellet).

[Preparation of positive electrode layer 2 (when using a sulfur composite)
Weigh the sulfur powder as the positive electrode active material, 75Li ₂ S-25P ₂ S ₅ glass as the sulfide-based lithium ion conductive solid electrolyte, and ketjen black so that the mass ratio is 6: 6: 1. The mixture was mixed at 380 rpm for 1 hour using a planetary ball mill to prepare a sulfur composite material.

  The produced sulfur composite material (30 mg) was uniformly arranged on a SUS substrate, and press-molded at a pressure of 180 MPa to produce a positive electrode layer 20 (positive electrode pellet).

[Production of all-solid-state batteries]
A 300 μm-thick sintered body (LAGP sintered body) formed of Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ was prepared as the solid electrolyte layer 40, and the positive electrode layer 20, LAGP sintered body (solid electrolyte) The layer 40) and the negative electrode layer 30 were stacked in this order and fixed at a pressure of 50 MPa to prepare a sample of the all-solid-state battery 10. In this experimental example, a sample of the all-solid-state battery 10 was produced using the negative electrode layer samples A1 to A5 and the positive electrode layer 20 formed of the LTO composite material.

B-3. experimental method:
While measuring the bulk density of produced negative electrode layer sample A1-A5, the surface observation by SEM (Scanning Electron Microscope) was performed, and the presence or absence of the crack was investigated. Moreover, the internal resistance in the all-solid-state battery 10 produced using negative electrode layer sample A1-A5 was measured. Specifically, the resistance value in the electrode layer was determined by separating a component considered to be interface resistance from the waveform obtained by impedance measurement. Moreover, the particle diameter of the Li-Al alloy contained in the negative electrode layer 30 was measured by observing a cut surface, a fracture surface, or the like with an SEM.

B-4. Experimental result:
2, 3, 5, and 6 are images showing the results of surface observation of the negative electrode layer samples A1, A2, A3, and A5. FIG. 4 is an enlarged image showing a portion surrounded by a white frame in FIG. The images shown in the (A) column of FIGS. 2, 3, 5 and 6 and the image shown in FIG. 4 are photographs taken by SEM, and the images shown in the (B) column of FIGS. It is the image which identified the position where Li-Al alloy powder exists by elemental analysis.

  According to these figures, in the negative electrode layer sample A1 (particle diameter of 300 μm or less, FIG. 2), as shown by the arrows in the figure, many cracks are generated in the particles of the Li—Al alloy powder. Understandable. In addition, in the negative electrode layer sample A2 (particle diameter of 200 μm or less, FIGS. 3 and 4), it can be understood that some cracks are generated in the particles of the Li—Al alloy powder as indicated by the arrows in the drawings. On the other hand, in the negative electrode layer sample A3 (particle diameter of 100 μm or less, FIG. 5) and the negative electrode layer sample A5 (particle diameter of 15 μm or less, FIG. 6), it is understood that cracks are not generated in the particles of the Li—Al alloy powder. it can.

FIG. 7 is an explanatory diagram showing, in a tabular form, experimental results regarding the particle diameter of the Li—Al alloy powder. The criteria for comprehensive evaluation in this experimental example are as follows.
Comprehensive evaluation “A”: no crack and resistance value of 8.0Ω or less Comprehensive evaluation “B”: crack and resistance value of 8.0Ω or less Comprehensive evaluation “C”: crack and resistance value Greater than 8.0Ω

  According to FIG. 7, it can be understood that the smaller the particle diameter of the Li—Al alloy powder, the harder the cracks are generated, and the smaller the number of cracks, the smaller the internal resistance when the all-solid-state battery 10 is produced. Specifically, cracks occurred in the negative electrode layer samples A1 and A2, and the overall evaluation was “B” or “C”. On the other hand, in the negative electrode layer samples A3 to A5, no crack was generated, the resistance values were all 7.5Ω or less, and the overall evaluation was “A”.

  From the above, it can be understood that the particle diameter of the Li—Al alloy powder is preferably 100 μm or less. Moreover, it is considered that cracks are less likely to occur as the particle diameter of the Li—Al alloy powder is smaller. Therefore, the particle diameter of the Li—Al alloy powder is more preferably 30 μm or less, and particularly preferably 15 μm or less. preferable.

C. Experimental example on bulk density of negative electrode layer:
C-1. Overview:
In this experimental example, in order to investigate the relationship between the bulk density of the negative electrode layer 30 and the internal resistance of the all solid state battery 10 when the particle diameter of the Li—Al alloy powder contained in the negative electrode layer 30 is constant. A plurality of samples of negative electrode layers 30 having different bulk densities were produced. Samples of negative electrode layers 30 having different bulk densities were produced by press molding with different applied pressures. In this experimental example, the relationship between the bulk density of the negative electrode layer 30 and the discharge capacity of the all-solid battery 10 was also examined.

C-2. Sample preparation:
[Preparation of negative electrode layer]
By arranging Li-Al composite material 5 (15 mg or 10 mg) produced by the above method uniformly on a SUS substrate and press-molding with different pressures, the following seven types of negative electrode layers 30 ( A sample of negative electrode pellet) was prepared.
Negative electrode layer sample B1: Li-Al composite material 5, applied pressure 54 MPa
Negative electrode layer sample B2: Li—Al composite material 5, applied pressure 90 MPa
Negative electrode layer sample B3: Li—Al composite material 5, applied pressure 108 MPa
Negative electrode layer sample B4: Li—Al composite material 5, applied pressure 144 MPa
Negative electrode layer sample B5: Li-Al composite material 5, applied pressure 180 MPa
Negative electrode layer sample B6: Li—Al composite material 5, applied pressure 270 MPa
Negative electrode layer sample B7: Li—Al composite material 5, applied pressure 360 MPa
The negative electrode layer sample B5 is the same as the negative electrode layer sample A5.
[Preparation of positive electrode layer]
Since the method for producing the sample of the positive electrode layer 20 is the same as that in the above experimental example, the description thereof is omitted.

[Production of all-solid-state batteries]
A 300 μm-thick sintered body (LAGP sintered body) formed of Li _1.5 Al _0.5 Ge _1.5 (PO ₄ ) ₃ was prepared as the solid electrolyte layer 40, and the positive electrode layer 20, LAGP sintered body (solid electrolyte) Layer 40) and the negative electrode layer 30 were stacked in this order and fixed at a pressure of 50 MPa to produce an all-solid-state battery 10.

  In this experimental example, a sample of the all solid state battery 10 including the positive electrode layer 20 formed of the LTO composite material and a sample of the all solid state battery 10 including the positive electrode layer 20 formed of the sulfur composite material were produced. When preparing a sample of the all-solid-state battery 10 including the positive electrode layer 20 formed of the LTO composite material, the negative electrode layer samples B1 to B7 prepared by press-molding 15 mg of the Li—Al composite material 5 Was used. On the other hand, when producing the sample of the all-solid-state battery 10 provided with the positive electrode layer 20 formed of sulfur composite material, the negative electrode layer sample B1 produced by press-molding 10 mg of Li-Al composite material 5 ~ B7 was used.

C-3. experimental method:
While measuring the bulk density of produced negative electrode layer sample B1-B7, the surface observation by SEM was performed and the presence or absence of the crack was investigated. Moreover, the internal resistance in the sample of an all-solid-state battery provided with negative electrode layer sample B1-B7 was measured. Specifically, the resistance value in the electrode layer was determined by separating a component considered to be interface resistance from the waveform obtained by impedance measurement. In addition, the resistance value was measured only when the LTO composite material was used as the positive electrode layer 20. Moreover, the particle diameter of the Li-Al alloy contained in the negative electrode layer 30 was measured by observing a cut surface, a fracture surface, or the like with an SEM.

  Furthermore, in this experiment example, the discharge capacity [mAh / g] of the all-solid-state battery 10 including the negative electrode layer samples B1 to B7 was examined. Specifically, the discharge capacity was examined for both the case where the LTO composite material was used as the positive electrode layer 20 and the case where the sulfur composite material was used as the positive electrode layer 20. The discharge capacity was determined by dividing by the mass of the negative electrode layer 30.

For the all-solid-state cell 10 LTO mixture material is used as the positive electrode layer 20, a constant current charge and discharge test, the voltage range 1.9V～0.7V, at a current density of 1.28mA / cm ^{2 2} Repeatedly, the discharge capacity at the second cycle where the value was more stable was determined. In this experimental example, the positive electrode active material contained in the LTO composite material used as the positive electrode layer 20 is about 10% with respect to the theoretical capacity of the Li—Al composite material used as the negative electrode layer 30. For this reason, the all-solid-state battery 10 in which the LTO composite material is used as the positive electrode layer 20 can be charged and discharged to a discharge depth of about 10% with respect to the negative electrode active material used for the negative electrode. Moreover, the discharge capacity calculated | required by this experiment example is based on the Li-Al alloy which is a negative electrode active material.

On the other hand, for the all-solid-state cell 10 sulfur mixture material is used as the positive electrode layer 20, a constant current charge and discharge test, the voltage range 3.0V～0.5V, a current density of 0.64mA / cm ² The discharge capacity at the second cycle, where the value was more stable, was determined by repeating the process twice. In this experimental example, the positive electrode active material contained in the sulfur composite used as the positive electrode layer 20 is about 200% with respect to the theoretical capacity of the Li—Al composite used as the negative electrode layer 30. Therefore, the all-solid-state battery 10 in which the sulfur composite material is used as the positive electrode layer 20 can be charged and discharged to a discharge depth exceeding 100% with respect to the negative electrode active material used for the negative electrode. Moreover, the discharge capacity calculated | required by this experiment example is based on the Li-Al alloy which is a negative electrode active material.

C-4. Experimental result:
FIG. 8 is an explanatory diagram showing the relationship between the pressure applied during the press molding of the negative electrode layer 30 and the bulk density of the negative electrode layer 30 in a graph format. The particle size of the Li—Al alloy particles contained in the negative electrode layer 30 in FIG. 8 is 15 μm or less. According to FIG. 8, it can be understood that the bulk density of the negative electrode layer 30 increases as the pressing force during press molding increases. However, it can be understood that when the applied pressure is 180 MPa or more, the increase in bulk density becomes moderate.

FIG. 9 is an explanatory diagram showing the relationship between the bulk density of the negative electrode layer 30 and the internal resistance of the all solid state battery 10 in a graph format. According to FIG. 9, it can be understood that as the bulk density increases, the internal resistance (resistance value in the electrode layer) of the all-solid battery 10 decreases. However, it can be understood that when the bulk density is 1.30 g / cm ³ or more, the decrease in internal resistance is moderate.

FIG. 10 is an explanatory diagram summarizing the experimental results regarding the bulk density of the negative electrode layer 30 in a tabular format. The criteria for comprehensive evaluation in FIG. 10 are as follows.
Comprehensive evaluation “A”: Resistance value is 8.0Ω or less Comprehensive evaluation “B”: Resistance value is greater than 8.0Ω and 10.0Ω or less Comprehensive evaluation “C”: Resistance value is greater than 10.0Ω

According to FIG. 10, it can be understood that as the bulk density of the negative electrode layer 30 increases, the internal resistance of the all solid state battery 10 decreases and the discharge capacity increases. Specifically, when the bulk density of the negative electrode layer 30 is less than 1.30 (samples B1 to B4), the internal resistance of the all-solid-state battery 10 is greater than 8.0Ω, and the overall evaluation is “B”. Or “C”. On the other hand, when the bulk density of the negative electrode layer 30 is 1.30 g / cm ³ or more (samples B5 to B7), the resistance value is 8.0Ω or less, and the overall evaluation is “A”. . From the above, it can be understood that the bulk density of the negative electrode layer 30 is preferably 1.30 g / cm ³ or more.

  The Li—Al composite used in the above experimental example contained Li—Al alloy powder and sulfide-based lithium ion conductive solid electrolyte in a mass ratio of 50:50 (1: 1). A sample of Li-Al composite material having a mass ratio of Li-Al alloy powder and sulfide-based lithium ion conductive solid electrolyte of 40:60 to 90:10 was prepared and the same experiment as described above was performed. The same results as above were obtained. Therefore, it can be understood that the mass ratio between the Li—Al alloy powder and the sulfide-based lithium ion conductive solid electrolyte contained in the Li—Al composite material may be arbitrarily set.

D. Variations:
The present invention is not limited to the above-described embodiments and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are possible.

・ Modification 1:
In the above embodiment, among the particles of the Li—Al alloy contained in the negative electrode layer 30, the particle diameter of particles having a mass ratio of 95% or more is 100 μm or less. In the above embodiment, the reason for defining “particles with a mass ratio of 95% or more” is that the internal resistance of the all-solid-state battery 10 is reduced even if the particle diameter of all the particles is not 100 μm or less. Because you can. However, the particle diameter of all the particles of the Li—Al alloy contained in the negative electrode layer 30 is more preferably 100 μm or less. In this way, the internal resistance of the all solid state battery 10 can be further reduced.

Modification 2
In the above embodiment, among the Li-Al alloy particles contained in the negative electrode layer 30, the particle diameter of particles having a mass ratio of 95% or more is 100 μm or less, and the bulk density of the negative electrode layer 30 is 1.30 g / cm ³ or more. However, the bulk density of the negative electrode layer 30 may be less than 1.30 g / cm ³ .

  The present invention is not limited to the above-described embodiments, examples, and modifications, and can be realized with various configurations without departing from the spirit thereof. For example, the technical features in the embodiments, examples, and modifications corresponding to the technical features in each embodiment described in the summary section of the invention are to solve some or all of the above-described problems, or In order to achieve part or all of the above effects, replacement or combination can be performed as appropriate. Further, if the technical feature is not described as essential in the present specification, it can be deleted as appropriate.

DESCRIPTION OF SYMBOLS 10 ... All-solid-state battery 15 ... Battery main body 20 ... Positive electrode layer 30 ... Negative electrode layer 40 ... Solid electrolyte layer 50 ... Current collector 60 ... Current collector

Claims (3)

A positive electrode layer containing a positive electrode active material;
A negative electrode layer containing a negative electrode active material;
An all-solid battery comprising a solid electrolyte layer positioned between the positive electrode layer and the negative electrode layer,
The solid electrolyte layer is formed of an oxide-based solid electrolyte material,
The negative electrode layer contains a lithium-aluminum alloy as the negative electrode active material, and further contains a sulfide-based solid electrolyte material,
An all-solid-state battery characterized in that, among the lithium-aluminum alloy particles contained in the negative electrode layer, particles having a mass ratio of 95% or more have a particle size of 100 μm or less. The all-solid-state battery according to claim 1,
The all-solid-state battery, wherein the negative electrode layer has a bulk density of 1.30 g / cm ³ or more. A method for producing an all-solid battery comprising a positive electrode layer, a negative electrode layer, and a solid electrolyte layer positioned between the positive electrode layer and the negative electrode layer,
(A) including a positive electrode active material to form the positive electrode layer;
(B) including a negative electrode active material to form the negative electrode layer;
(C) forming the solid electrolyte layer using an oxide-based solid electrolyte material,
The step (b) includes a step of using a lithium-aluminum alloy as the negative electrode active material and further containing a sulfide-based solid electrolyte material with respect to the negative electrode layer.
Of the lithium-aluminum alloy particles contained in the negative electrode layer in the step (b), the particle size of particles having a mass ratio of 95% or more is 100 μm or less. Production method.