JP2013149373A - Solid electrolyte material, all-solid-state battery, and method for manufacturing solid electrolyte material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid electrolyte material that contains Li and B, and has a POstructure and high Li ion conductivity.SOLUTION: The solid electrolyte material contains Li and B, and has a POstructure and a crystallite size of 50 nm or smaller.

Description

The present invention relates to a solid electrolyte material having a Li element, a B element, and a PO ₄ structure and high Li ion conductivity.

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

  Currently marketed lithium-ion batteries use electrolytes containing flammable organic solvents, so safety devices that prevent temperature rise during short circuits and improvements in structure and materials to prevent short circuits Is required. In contrast, an all-solid-state lithium ion battery in which the electrolyte is changed to a solid electrolyte layer to make the battery all solid does not use a flammable organic solvent in the battery. And is considered to be highly productive.

As an inorganic solid electrolyte material, a solid electrolyte material (LBPO) having a Li element, a B element, and a PO ₄ structure is known. For example, Patent Document 1 discloses an all solid state secondary battery including an inorganic solid electrolyte that is sintered by applying a direct current pulse current under pressure, and LiBPO ₄ is cited as an example of the inorganic solid electrolyte. Non-Patent Documents 1 to 4 also disclose LBPO as a solid electrolyte material exhibiting Li ion conductivity.

Japanese Patent Laid-Open No. 2000-200621

E.M.Kelder et al., “A new ceramic lithium solid electrolyte for rechargeable swing type batteries”, Solid State Ionics 85 (1996) 285-291 M.J.G.Jak et al., “Lithium Ion Conductivity of a Statically and Dynamically Compacted Nano-structured Ceramic Electrolyte for Li-Ion Batteries”, Journal of Electroceramics 2: 2, 127-134, 1998 M.J.G.Jak et al., “Composite cell components for elevated temperature all-solid-state Li-ion batteries”, Solid State Ionics 143 (2001) 57-66 Tae Jung Kim et al., “Ionic conductivity of LixB1-x / 3 PO4 ceramic electrolyte based on defect models”, Journal of Power Sources 123 (2003) 65-68

  Conventionally, it is known that LBPO exhibits Li ion conductivity. However, LBPO is a material having lower Li ion conductivity than other high Li ion conductive solid electrolyte materials (for example, LATP). Recognized. On the other hand, from the viewpoint of increasing the output of the battery, the solid electrolyte material is required to improve Li ion conductivity.

The present invention has been made in view of the above circumstances, and has as its main object to provide a solid electrolyte material having a Li element, a B element, and a PO ₄ structure and high Li ion conductivity.

In order to improve the Li ion conductivity of the solid electrolyte material having a Li element, B element, and PO ₄ structure as a result of extensive research conducted by the present inventors in order to solve the above-mentioned problems, it is completely different from the conventional case. We have found that it is effective to adopt the reverse approach. Although details will be described later, in general, when the Li ion conductivity in the crystal grain is compared with the Li ion conductivity in the crystal grain boundary, the Li ion conductivity in the crystal grain having no grain boundary resistance is high. It is considered. Therefore, it is considered effective to increase the size of crystals (strictly, crystallites) in order to improve Li ion conductivity. On the other hand, in the solid electrolyte material having Li element, B element, and PO ₄ structure, it has been surprisingly found that reducing the crystallite size is effective in improving Li ion conductivity, and the present invention. It came to complete.

That is, the present invention provides a solid electrolyte material having a Li element, a B element, and a PO ₄ structure and having a crystallite size of 50 nm or less.

  According to the present invention, since the crystallite size is a predetermined value or less, a solid electrolyte material having high Li ion conductivity can be obtained.

  In the said invention, it is preferable that the relative density with respect to a theoretical density is 80% or more. This is because the Li ion conductivity is further improved.

  In the present invention, a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid electrolyte formed between the positive electrode active material layer and the negative electrode active material layer An all-solid-state battery, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer contains the above-described solid electrolyte material. To do.

  According to the present invention, at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer contains the above-described solid electrolyte material, whereby a high output battery can be obtained.

Further, in the present invention, a method for producing a solid electrolyte material having a Li element, B element, and PO ₄ structure, wherein the crystallite size is reduced to 50 nm or less by applying pressure to the raw material particles of the solid electrolyte material. There is provided a method for producing a solid electrolyte material, comprising a pressure applying step.

  According to the present invention, a solid electrolyte material having high Li ion conductivity can be obtained by setting the crystallite size to a predetermined value or less in the pressure application step.

  In the said invention, it is preferable to give the said raw material particle the pressure of 500 Mpa or more in the said pressure provision process.

  In the said invention, it is preferable to give a pressure to the said raw material particle by the aerosol deposition method in the said pressure provision process.

  The solid electrolyte material of the present invention has an effect of high Li ion conductivity.

It is a schematic diagram explaining the difference in Li ion conduction mechanism. It is a schematic diagram explaining a crystallite. It is a schematic sectional drawing which shows an example of the all-solid-state battery of this invention. It is a schematic diagram explaining the aerosol deposition method. 2 is a SEM image of raw material particles used in Example 1 and a solid electrolyte membrane produced in Example 1. FIG. It is a result of the XRD measurement with respect to the solid electrolyte membrane produced in Examples 1-3. It is a result of Li ion conductivity measurement with respect to the evaluation member obtained in Examples 1-3. It is a result of Li ion conductivity measurement with respect to the evaluation member obtained by the comparative example.

  Hereinafter, the solid electrolyte material, the all-solid battery, and the method for producing the solid electrolyte material of the present invention will be described in detail.

A. First, the solid electrolyte material of the present invention will be described. The solid electrolyte material of the present invention is a solid electrolyte material having a Li element, a B element, and a PO ₄ structure, and has a crystallite size of 50 nm or less.

According to the present invention, since the crystallite size is a predetermined value or less, a solid electrolyte material having high Li ion conductivity can be obtained. Here, the difference in Li ion conduction mechanism between LBPO and a conventional solid electrolyte material will be described with reference to FIG. In addition, LATP is mentioned as an example of the conventional solid electrolyte material. LATP is a solid electrolyte material having a Li, Al, Ti, PO ₄ structure (for example, Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ ). In FIG. 1, G means the inside of a crystal grain, GB means a crystal grain boundary, and σ means Li ion conductivity. A solid electrolyte material A having a large crystallite size (low grain boundary density) as shown in FIG. 1A and a solid electrolyte material B having a small crystallite size (high grain boundary density) as shown in FIG. And σ _A >> σ _{B in} a normal solid electrolyte material such as LATP. This is because the Li ion conductivity σ _G in the crystal grain _G where the size of the channel through which Li passes is constant is overwhelmingly higher than the Li ion conductivity σ _GB in the crystal grain boundary GB.

That is, in a normal solid electrolyte material, the crystal grain boundary becomes the rate-determining factor for Li ion conduction, so to improve Li ion conductivity, it is necessary to increase the crystallite size (ultimately to be a single crystal). It is considered effective. For example, Kai-Yun Yang et al., “Roles of lithium ions and La / Li-site vacancies in sinterability and total ionic conduction properties of cyclic Li _3x La _{2 / 3-x} TiO ₃ solid electrolytes (0.21 <3x < 0.50) ”, Journal of Alloys and Compounds 458 (2008) 415-424 discloses that increasing the sintering temperature and increasing the crystallite size reduces the grain boundaries and lowers the grain boundary resistance. Yes.

On the other hand, in LBPO, as described in the examples described later, σ _A << σ _B unexpectedly. The reason is not necessarily clear, but LBPO is different from a normal solid electrolyte material because Li ion conductivity σ _{GB at the} grain boundary GB is higher than Li ion conductivity σ _{G at the} crystal grain G. It is believed that there is. That is, it is suggested that the crystal grain boundary, which has been conventionally considered to be the rate-determining mechanism of Li ion conduction, actually has higher Li ion conductivity than the crystal grains, and the Li ion conduction mechanism is completely different. The reason why the Li ion conductivity at the grain boundary is high is probably that the Li ion concentration at the grain boundary is increased, and the structure of weakly bonded atoms at the grain boundary (semi-solid structure, amorphous-like structure). The influence by can be considered. Due to such unique properties, the solid electrolyte material of the present invention is considered to be a material having high Li ion conductivity.

  On the other hand, although Non-Patent Documents 1 to 4 disclose LBPO, there is no description or suggestion that the Li ion conductivity is improved by reducing the crystallite size. As a result of experiments using the AD method described later, the present inventors have found that LBPO has higher Li ion conductivity as the crystallite size is smaller. The Li ion conductivity of the polycrystalline solid electrolyte material largely depends mainly on the density and the crystallite size, but it is difficult to change the crystallite size while keeping the density constant by the conventional method. On the other hand, in the AD method, a dense film can be formed by utilizing the normal temperature impact solidification phenomenon described later, and therefore the change in Li ion conductivity due to the difference in crystallite size was confirmed under the condition where the density was almost constant. did it. Such knowledge is obtained only by the inventors who are familiar with the AD method.

The solid electrolyte material of the present invention has a Li element, a B element, and a PO ₄ structure. Examples of the composition of the solid electrolyte material of the present invention include xLi ₂ O—BPO ₄ (0.5 ≦ x ≦ 1.5), Li _x B _{1-x / 3} PO ₄ (0.75 ≦ x <3), and the like. Can be mentioned. Further, the ratio of Li to B (mol basis) is preferably 1 or more. Further, the solid electrolyte material of the present invention may be composed only of Li element, B element, and PO ₄ structure, or composed only of Li element, B element, O element, and PO ₄ structure. Alternatively, at least one element of Li, B, P, and O may be partially substituted with another element.

The present invention is greatly characterized in that the crystallite size of the solid electrolyte material is in a specific range. Here, the crystallite refers to the largest group that can be regarded as a single crystal, and as shown in FIG. 2, a plurality of crystallites constitute a particle (polycrystalline particle). In addition, although particle | grains are illustrated in FIG. 2, the solid electrolyte material of this invention may be a film | membrane form. The crystallite size of the solid electrolyte material is usually 50 nm or less, and is preferably smaller from the viewpoint of improving Li ion conductivity. Specifically, it is preferably 40 nm or less, and more preferably 30 nm or less. The crystallite size can be determined from the full width at half maximum (FWHM) of the XRD peak. Specifically, XRD measurement is performed on the solid electrolyte material using CuKα rays, and the FWHM (°) of the peak around 2θ = 24.7 ° is obtained. By substituting this FWHM value into the following formula (Scherrer formula), the crystal size D can be calculated.
D = Kλ / (βcosθ)
K: Scherrer constant, λ: wavelength, β: diffraction line broadening depending on crystallite size, θ: diffraction angle 2θ / θ
In addition, the solid electrolyte material of the present invention preferably has peaks at positions of 2θ = 24.7 °, 39.9 °, and 48.8 ° in XRD measurement using CuKα rays. The peak position may be back and forth within a range of ± 0.5 °.

  The relative density of the solid electrolyte material of the present invention is not particularly limited, but is preferably in the range of 80% to 99%, for example, and more preferably in the range of 90% to 99%. If the relative density of the solid electrolyte material is too high (for example, exceeding 100%), the solid electrolyte material may be distorted. If the solid electrolyte material is too low, the solid electrolyte material will not be dense and sufficient This is because ionic conductivity may not be obtained. The relative density of the solid electrolyte material can be obtained by dividing the actual density of the solid electrolyte material by the theoretical density of the solid electrolyte material. The actual density of the solid electrolyte material can be obtained, for example, by obtaining the volume of the solid electrolyte material from the area and film thickness of the solid electrolyte material and dividing the weight of the solid electrolyte material by the volume.

The solid electrolyte material of the present invention preferably has a high Li ion conductivity at room temperature (25 ° C.). Li ion conductivity is, for example, preferably 1 × 10 ⁻⁶ S / cm or more, more preferably 1 × 10 ⁻⁵ S / cm or more, and 1 × 10 ⁻⁴ S / cm or more. Is more preferable, and 1 × 10 ⁻³ S / cm or more is particularly preferable. Li ion conductivity can be obtained by an AC impedance method.

  In addition, the shape of the solid electrolyte material of the present invention is not particularly limited, and may be a film shape or a particle shape. The membrane-like solid electrolyte material can be obtained by using, for example, an aerosol deposition method as described later. On the other hand, the particulate solid electrolyte material can be obtained, for example, by pulverizing a membrane solid electrolyte material.

B. Next, the all solid state battery of the present invention will be described. The all solid state battery of the present invention includes a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid formed between the positive electrode active material layer and the negative electrode active material layer. An all-solid battery having an electrolyte layer, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer contains the above-described solid electrolyte material.

  FIG. 3 is a schematic cross-sectional view showing an example of the all solid state battery of the present invention. 3 is formed between a positive electrode active material layer 1 containing a positive electrode active material, a negative electrode active material layer 2 containing a negative electrode active material, and between the positive electrode active material layer 1 and the negative electrode active material layer 2. The solid electrolyte layer 3, the positive electrode current collector 4 that collects current from the positive electrode active material layer 1, the negative electrode current collector 5 that collects current from the negative electrode active material layer 2, and a battery case that houses these members 6. In the present invention, at least one of the positive electrode active material layer 1, the negative electrode active material layer 2 and the solid electrolyte layer 3 contains the solid electrolyte material described in “A. Solid electrolyte material”.

According to the present invention, at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer contains the above-described solid electrolyte material, whereby a high output battery can be obtained.
Hereinafter, the all solid state battery of the present invention will be described for each configuration.

1. Positive electrode active material layer The positive electrode active material layer in the present invention is a layer containing at least a positive electrode active material, and may contain at least one of a solid electrolyte material, a conductive material and a binder, if necessary. good. As a positive electrode active material, an oxide active material etc. can be mentioned, for example. Examples of the oxide active material include lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), LiNi _1/3 Mn _1/3 Co _1/3 O ₂ , lithium manganate (LiMn ₂ O ₄ ), Li _{1 + x} Mn _2−xy M _y O ₄ (M is one or more selected from Al, Mg, Co, Fe, Ni, Zn, 0 ≦ x + y ≦ 2) Examples thereof include lithium titanate, lithium metal phosphate (LiMPO ₄ , M is one or more selected from Fe, Mn, Co, and Ni), vanadium oxide (V ₂ O ₅ ), and molybdenum oxide (MoO ₃ ).

  The positive electrode active material layer in the present invention may contain a solid electrolyte material. By adding the solid electrolyte material, the Li ion conductivity of the positive electrode active material layer can be improved. Especially, it is preferable that the solid electrolyte material contained in a positive electrode active material layer is the solid electrolyte material described in the said "A. solid electrolyte material". This is because a high output battery can be obtained. In particular, the positive electrode electrolyte layer in the present invention preferably contains the above-described particulate solid electrolyte material. Moreover, the positive electrode active material layer may contain a conductive material. By adding a conductive material, the conductivity of the positive electrode active material layer can be improved. Examples of the conductive material include acetylene black, ketjen black, and carbon fiber. The positive electrode active material layer may contain a binder. Examples of the type of binder include fluorine-containing binders such as polyvinylidene fluoride (PVDF). The thickness of the positive electrode active material layer is preferably in the range of 0.1 μm to 1000 μm, for example.

2. Negative electrode active material layer The negative electrode active material layer in the present invention is a layer containing at least a negative electrode active material, and may contain at least one of a solid electrolyte material, a conductive material and a binder, if necessary. good. Examples of the negative electrode active material include a metal active material and a carbon active material. Examples of the metal active material include In, Al, Si, and Sn. On the other hand, examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. An oxide active material may be used as the negative electrode active material. Examples of the oxide active material include compounds containing Li, Ti, and O (for example, Li ₄ Ti ₅ O ₁₂ ).

  The negative electrode active material layer in the present invention may contain a solid electrolyte material. The addition of the solid electrolyte material can improve the Li ion conductivity of the negative electrode active material layer. Especially, it is preferable that the solid electrolyte material contained in a negative electrode active material layer is the solid electrolyte material described in the said "A. solid electrolyte material". This is because a high output battery can be obtained. In particular, the negative electrode electrolyte layer in the present invention preferably contains the above-described particulate solid electrolyte material. Further, the conductive material and the binder contained in the negative electrode active material layer are the same as those described in “1. Positive electrode active material layer”. The thickness of the negative electrode active material layer is preferably in the range of 0.1 μm to 1000 μm, for example.

3. Solid electrolyte layer The solid electrolyte layer in this invention is a layer formed between a positive electrode active material layer and a negative electrode active material layer. The solid electrolyte material constituting the solid electrolyte layer is not particularly limited as long as it has Li ion conductivity, but is preferably the solid electrolyte material described in the above “A. Solid electrolyte material”. . This is because a high output battery can be obtained. In particular, the solid electrolyte layer in the present invention is preferably composed of the above-described membrane-shaped solid electrolyte material. The thickness of the solid electrolyte layer is, for example, preferably in the range of 0.1 μm to 1000 μm, and more preferably in the range of 0.1 μm to 300 μm.

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

5. All-solid battery The all-solid battery of the present invention may be a primary battery or a secondary battery, but is preferably a secondary battery. For example, it is useful as a vehicle battery. Examples of the shape of the all solid state battery of the present invention include a coin type, a laminate type, a cylindrical type, and a square type.

C. Next, a method for producing a solid electrolyte material of the present invention will be described. The method for producing a solid electrolyte material of the present invention is a method for producing a solid electrolyte material having a Li element, B element, and PO ₄ structure, and by applying pressure to the raw material particles of the solid electrolyte material, the crystallite size Having a pressure applying step of adjusting the thickness to 50 nm or less.

  According to the present invention, a solid electrolyte material having high Li ion conductivity can be obtained by setting the crystallite size to a predetermined value or less in the pressure application step.

The pressure applying step in the present invention is a step of applying pressure to the raw material particles of the solid electrolyte material having a Li element, a B element, and a PO ₄ structure. By this step, the crystallite size is set to 50 nm or less. The preferred range of the crystallite size is the same as that described in the above “A. Solid electrolyte material”, and the description is omitted here.

The raw material particles used in the present invention usually have a Li element, a B element, and a PO ₄ structure. The composition of the raw material particles is preferably the same as the composition of the solid electrolyte material described above. Further, in the raw material particles, the ratio of Li to B (mol basis) is preferably 1 or more. This is because even when Li is volatilized, a solid electrolyte material having good Li ion conductivity can be obtained. In the present invention, the crystallinity of the raw material particles may be improved in advance by heat treatment. This is because by improving the crystallinity in advance, it becomes easier to produce a solid electrolyte material having a desired crystallite size. In the present invention, the average particle diameter of the raw material particles may be refined in advance. This is because it becomes easy to produce a solid electrolyte material having a desired crystallite size by miniaturization in advance. Examples of the method for miniaturization include mechanical milling such as a ball mill. Furthermore, a predetermined classification may be performed on the refined raw material particles. The average particle diameter _{D 50} of the raw material particles is not particularly limited, for example, is preferably in the range of 0.4Myuemu～4myuemu, and more preferably in a range of 0.6Myuemu～2myuemu. The crystallite size of the raw material particles is not particularly limited, but is preferably in the range of 10 nm to 80 nm, for example, and more preferably in the range of 10 nm to 50 nm.

  In the present invention, pressure is applied to the raw material particles. The pressure applied to the raw material particles is preferably high enough to obtain a desired crystallite size, specifically 500 MPa or more, more preferably 1 GPa or more, and 1.2 GPa or more. More preferably.

  The pressure application method for applying pressure to the raw material particles is not particularly limited as long as a desired crystallite size can be obtained, but a method in which the raw material particles are not actively heated is preferable. This is because it is possible to prevent grain growth from occurring due to heating and increase in crystallite size. Further, the pressure applying method may be a method of applying pressure to the raw material particles by collision with the substrate, or a method of applying pressure to the raw material particles by a pressure medium.

  An example of a method for applying pressure to the raw material particles by collision with the substrate is an aerosol deposition method (AD method). The AD method uses a “normal temperature impact solidification phenomenon” (a phenomenon in which only mechanical impact force is applied to the raw material particles and solidifies at a normal temperature without heating) to obtain a dense and highly adhesive film. be able to. Furthermore, although it depends on the material of the film, there is an advantage that the film forming speed is several tens of times that of the conventional thin film forming technique. Further, since a high pressure is applied only to a very limited area of the substrate, there are advantages that damage to the substrate is small and mutual diffusion due to heat does not occur.

  FIG. 4 is a schematic diagram for explaining the aerosol deposition method (AD method). In FIG. 4, a pedestal 12 is installed inside the chamber 11, and a substrate 13 is disposed on the pedestal 12. Moreover, the pressure inside the chamber 11 can be controlled to an arbitrary reduced pressure state by the rotary pump 14. On the other hand, the raw material particles 16 are aerosolized by the carry-in gas supplied from the gas cylinder 15 inside the aerosol generator 17. Further, the aerosolized raw material particles are sprayed toward the substrate 13 from the nozzle 18 disposed inside the chamber 11. On the surface of the substrate 13, deposition occurs along with destructive deformation (atomization) of particles, and a thin film is formed.

  The pressure P in the chamber at the time of film formation by the AD method is not particularly limited as long as it can obtain a desired density. For example, it is preferably higher than 100 Pa, more preferably 120 Pa or higher. More preferably, it is 150 Pa or more. This is because if the pressure during film formation is too low, the density of the active material layer may become too large. On the other hand, the pressure P is preferably 400 Pa or less, and more preferably 350 Pa or less, for example. This is because if the pressure during film formation is too high, it may be difficult to obtain a dense active material layer.

The type of carrier gas in the AD method, but not limited, helium (He), argon (Ar), nitrogen (N ₂₎ an inert gas, such as, and can include dry air, or the like. Also, the gas flow rate of the carrier gas is not particularly limited as long as it is a flow rate capable of maintaining a desired aerosol. For example, 3 L / min. ~ 8L / min. It is preferable to be within the range.

  Another example of the method of applying pressure to the raw material particles by collision with the substrate is a cold spray method.

  On the other hand, examples of the method of applying pressure to the raw material particles with a pressure medium include CIP (Cold Isostatic Pressing) and CUP (Cold Uniaxial Pressing). Another example of the pressure applying method is magnetic pulse compression.

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

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

[Example 1]
(Preparation of raw material particles)
First, LBPO (particles having 1.1 mol of Li with respect to 1 mol of BPO ₄ , average particle diameter D ₅₀ = 50 μm) was subjected to heat treatment under conditions of 600 ° C. for 6 hours in an air atmosphere to obtain crystallinity. Improved. The obtained LBPO was put in a planetary ball mill container and processed under conditions of a base plate rotation speed of 250 rpm for 2 hours to obtain raw material particles (average particle diameter D ₅₀ = 0.8 μm). The crystallite size of the raw material particles was 50 nm.

(Preparation of solid electrolyte membrane)
A solid electrolyte membrane was prepared by AD method using the obtained raw material particles. An Al alloy (A5052, thickness 0.5 mm) was used for the substrate. The film forming conditions are as follows.
<Film formation conditions>
・ Temperature Normal temperature ・ Pressure in the chamber 600Pa
・ Gas He
・ Gas flow rate 2L / min. (Assist gas 3L / min.)
・ Scanning speed 2.5mm / sec.
・ Distance between substrate nozzles 20mm
In this way, a solid electrolyte membrane was obtained on the substrate. Further, an Au thin film (current collecting part) was formed on the solid electrolyte film by sputtering to obtain an evaluation member.

[Example 2]
An evaluation member was obtained in the same manner as in Example 1 except that the conditions for forming the solid electrolyte membrane were changed as follows.
<Film formation conditions>
・ Temperature Normal temperature ・ Pressure in the chamber 200Pa
・ Gas He
・ Gas flow rate 1.5L / min. (Assist gas 3.5L / min.)
・ Scanning speed 2.5mm / sec.
・ Distance between substrate nozzles 15mm

[Example 3]
An evaluation member was obtained in the same manner as in Example 1 except that the conditions for forming the solid electrolyte membrane were changed as follows.
<Film formation conditions>
・ Temperature Normal temperature ・ Pressure in the chamber 100Pa
・ Gas O ₂
・ Gas flow rate 1.5L / min. (Assist gas 7.0L / min.)
・ Scanning speed 2.5mm / sec.
・ Distance between substrate nozzles 15mm

[Evaluation 1]
(SEM observation)
The raw material particles used in Example 1 and the solid electrolyte membrane (cross section) produced in Example 1 were observed using a scanning electron microscope. The result is shown in FIG. As shown in FIG. 5 (a), the raw material particles used in Example 1 are particles, and as shown in FIG. 5 (b), the solid electrolyte membrane produced in Example 1 has finely divided raw material particles. It was confirmed that the film was 15.9 μm thick.

(Density measurement)
The density of the solid electrolyte membrane produced in Examples 1 to 3 was calculated. First, the volume of the solid electrolyte membrane was determined from the area and film thickness of the solid electrolyte membrane. Next, the density of the solid electrolyte membrane was determined by measuring the weight of the solid electrolyte membrane and dividing the weight by the volume of the solid electrolyte membrane. The relative density was determined by dividing this value by the theoretical density. The results are shown in Table 1.

(Crystallite size measurement)
X-ray diffraction (XRD) measurement using CuKα rays was performed on the solid electrolyte membranes prepared in Examples 1 to 3. As a result, peaks were observed at 2θ = 24.7 °, 39.9 °, and 48.8 °. Further, as shown in FIG. 6, the crystallite size was calculated from the full width at half maximum (FWHM) of the peak at 2θ = 24.7 °. The crystallite size was calculated using the Scherrer equation described above.

(Li ion conductivity measurement)
Li ion conductivity measurement was performed on the evaluation members obtained in Examples 1 to 3. The measurement was performed by the AC impedance method. The results are shown in FIG.

  As shown in FIG. 7 and Table 1, in Examples 1 to 3, it was confirmed that the Li ion conductivity was improved as the crystallite size was reduced.

[Comparative Example 1]
(Preparation of raw material particles)
First, heat treatment was performed on Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ (average particle diameter D ₅₀ = 1.0 μm) under the conditions of air atmosphere, 700 ° C., 4 hours, Improved sex. The obtained Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ was put in a container of a planetary ball mill and processed under conditions of a base plate rotation of 200 rpm for 1 hour, and raw material particles (average particle diameter D ₅₀ = 0.8 μm).
(Preparation of solid electrolyte membrane)
A solid electrolyte membrane was prepared by AD method using the obtained raw material particles. The same Al alloy (A5052) as in the example was used for the substrate. The film forming conditions are as follows.
<Film formation conditions>
・ Temperature Normal temperature ・ Pressure in the chamber about 1 Torr
・ Gas He
・ Gas flow rate: 1L / min. To 10L / min
・ Scanning speed 0.1mm / sec.-10mm / sec.
In this way, a solid electrolyte membrane was obtained on the substrate. Further, an Au thin film (current collecting part) was formed on the solid electrolyte film by sputtering to obtain an evaluation member.

[Comparative Example 2]
First, uniaxial molding was performed at 100 MPa with respect to Li _1.3 Al _0.3 Ti _1.7 (PO ₄ ) ₃ (average particle size D ₅₀ = 1.0 μm). Next, CIP was performed at 150 MPa. Then, the pellet was produced by baking at 900 degreeC for 6 hours. An evaluation member was obtained using this pellet.

[Evaluation 2]
Crystallite size measurement and Li ion conductivity measurement were performed on the evaluation members obtained in Comparative Examples 1 and 2. The measurement method is as described above. The result is shown in FIG. As shown in FIG. 8, it was confirmed that the Li ion conductivity was improved as the crystallite size was increased, and it was confirmed that the tendency was completely opposite to that of LBPO.

DESCRIPTION OF SYMBOLS 1 ... Positive electrode active material layer 2 ... Negative electrode active material layer 3 ... Solid electrolyte layer 4 ... Positive electrode collector 5 ... Negative electrode collector 6 ... Battery case 10 ... All-solid-state battery 11 ... Chamber 12 ... Base 13 ... Substrate 14 ... Rotary Pump 15 ... Gas cylinder 16 ... Raw material particles 17 ... Aerosol generator 18 ... Nozzle

Claims (6)

A solid electrolyte material having a Li element, a B element, and a PO ₄ structure and having a crystallite size of 50 nm or less.   The solid electrolyte material according to claim 1, wherein a relative density with respect to a theoretical density is 80% or more. An all-solid battery having a positive electrode active material layer containing a positive electrode active material, a negative electrode active material layer containing a negative electrode active material, and a solid electrolyte layer formed between the positive electrode active material layer and the negative electrode active material layer Because
An all-solid battery, wherein at least one of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer contains the solid electrolyte material according to claim 1. A method for producing a solid electrolyte material having a Li element, a B element, and a PO ₄ structure,
A method for producing a solid electrolyte material, comprising a pressure application step of applying a pressure to the raw material particles of the solid electrolyte material to reduce a crystallite size to 50 nm or less.   The method for producing a solid electrolyte material according to claim 4, wherein, in the pressure applying step, a pressure of 500 MPa or more is applied to the raw material particles.   6. The method for producing a solid electrolyte material according to claim 4, wherein in the pressure application step, pressure is applied to the raw material particles by an aerosol deposition method.