JP2016051539A - Solid electrolytic material, and all-solid battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize: a solid electrolytic material which enables the suppression of the reduction in ion conductivity at a room temperature; and an all-solid battery which delivers desired good battery characteristics by use of such a solid electrolytic material.SOLUTION: A solid electrolytic material comprises a primary component having a Nasicon type crystal structure and expressed by the following general formula: LiZr(PO)where x is 0.1-0.4, preferably 0.1-0.2. An all-solid battery comprises: a solid electrolytic layer 4; a positive electrode layer 5 on one principal face of the solid electrolytic layer 4; and a negative electrode layer 6 on the other principal face of the solid electrolytic layer 4. The solid electrolytic layer 4 includes the solid electrolytic material as a primary component.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a solid electrolyte material and an all-solid battery, and more particularly to a solid electrolyte material used for an electrolyte of a secondary battery and an all-solid battery using the solid electrolyte material.

  In recent years, with the expansion of the market for portable electronic devices such as mobile phones, notebook computers, and digital cameras, secondary batteries have been actively developed as cordless power sources for these electronic devices. In addition, with the background of global warming and the depletion of petroleum resources, development of electric vehicles and hybrid vehicles using secondary batteries as a power source is also actively conducted.

  Under such circumstances, lithium ion secondary batteries using lithium ions as charge carriers and utilizing an electrochemical reaction associated with charge exchange are already in widespread use.

  However, in this type of lithium ion secondary battery, since a liquid electrolyte (electrolytic solution) mainly composed of an organic compound is usually used as a medium for transferring ions, the liquid electrolyte is used in the secondary battery. There is a risk of leakage from the can. Moreover, since the organic compound normally used as a liquid electrolyte is a combustible substance, sufficient safety cannot be ensured, and high temperature stability and durability are also inferior.

  For this reason, research on secondary batteries using solid electrolytes instead of liquid electrolytes has been actively conducted.

  For example, in Patent Document 1, in a solid electrolyte made of conductive ceramics, 40% by weight of an electrolyte made of the same kind of ionic conductor as the ceramic electrolyte and having a glass component higher than that of the ceramic electrolyte is used. Solid electrolytes added and sintered have been proposed below.

In this patent document 1, a solid electrolyte using the ionic conductivity of alkali metal ions or Ag ions is disclosed. For example, by adding 20% by weight of LiAlSiO ₄ to Li ₂ Zr (PO ₄ ) ₂ , A solid electrolyte having an ionic conductivity (conductivity) of 3.1 × 10 ⁻⁴ S / cm at a temperature of 300 ° C. has been obtained.

JP-A-6-80462 (Claim 1, Table 1, etc.)

  In a secondary battery, it is necessary to increase ion conductivity in order to ensure a desired large battery capacity. And in secondary batteries such as all-solid-state batteries that use solid electrolytes, it is possible to suppress the decrease in ionic conductivity by ensuring the crystal system of the crystal structure to be rhombohedral, and to ensure ionic conductivity. Is possible.

However, the Li ₂ Zr (PO ₄ ) ₂ -based material described above does not have a rhombohedral single-phase structure at room temperature, and it is difficult to ensure sufficient ion conductivity.

  That is, the Arrhenius equation (σ = A exp (−Ea / RT), A: frequency factor, R: gas constant, Ea: activation energy) is established between the ionic conductivity σ and the temperature T.

Therefore, in Patent Document _1, to obtain a _{Li 2 Zr (PO 4) 3.1} × 10 -4 S / cm of ion conductivity at a temperature of 300 ° C. By using the ₂ material (conductivity) Although it is possible, the ionic conductivity is extremely low at room temperature (for example, 25 ° C.). Further, Patent Document 1 discloses a solid electrolyte using the ionic conductivity of Na ions and Ag ions, both of which are measured at a high temperature of 300 ° C. In comparison, the ionic conductivity is extremely low.

  As described above, in Patent Document 1, since the ion conductivity at room temperature is low, and sufficient ion conductivity cannot be ensured at room temperature, it is difficult to obtain a desired good battery capacity.

  The present invention has been made in view of such circumstances, and a solid electrolyte material capable of suppressing a decrease in ion conductivity at room temperature, and desired good battery characteristics can be obtained by using this solid electrolyte material. It is an object to provide an all solid state battery.

In recent years, research and development of materials having a NASICON crystal structure represented by the general formula AY ₂ (XO ₄ ) ₃ have been actively conducted. In particular, a solid electrolyte material containing Zr in the central element Y is promising as a material for secondary batteries such as an all-solid battery because Zr has reduction resistance.

  Then, the present inventors conducted extensive research on a phosphoric acid compound having a NASICON crystal structure containing Li and Zr as the ion conductive substance A, and adjusting the mixing ratio of Li and Zr. As a result, it was found that the decrease in ionic conductivity can be suppressed even at room temperature.

  The present invention has been made based on such knowledge, and the solid electrolyte material according to the present invention is formed of an oxide having a NASICON crystal structure containing at least Li, Zr, and P as main components. The Li and the Zr are blended so that x is 0.1 to 0.4 when the blending ratio of the Li is (1 + 4x) and the blending ratio of the Zr is (2-x). It is characterized by being.

In the solid electrolyte material of the present invention, the main component is preferably represented by the general formula Li _{1 + 4x} Zr _2-x (PO ₄ ) ₃ (where 0.1 ≦ x ≦ 0.4). .

  Furthermore, in the solid electrolyte material of the present invention, the x is preferably 0.1 to 0.2.

  Thereby, crystallinity can be improved and a solid electrolyte material having better ion conductivity can be obtained.

  In the solid electrolyte material of the present invention, a part of Zr is substituted with at least one element selected from the names of Ca, Ba, Sr, Al, Sc, Y, In, and Hf. preferable.

  Thereby, temperature stability can be improved and the solid electrolyte material which has more stable ion conductivity can be obtained.

  The solid electrolyte material of the present invention preferably has a rhombohedral single-phase structure.

  An all solid state battery according to the present invention is an all solid state battery having a positive electrode layer on one main surface of a solid electrolyte layer and a negative electrode layer on the other main surface of the solid electrolyte layer, The layer is characterized by comprising as a main component the solid electrolyte material described above.

  In the all solid state battery of the present invention, it is preferable that at least one of the positive electrode layer and the negative electrode layer and the solid electrolyte layer are integrally sintered.

  As a result, it is possible to obtain a sintered all solid state battery that can be densely sintered at the sintering temperature and that can ensure good ion conductivity at room temperature.

  In the all solid state battery of the present invention, it is preferable that at least one of the positive electrode layer and the negative electrode layer contains the solid electrolyte material.

  According to the solid electrolyte material of the present invention, the main component is formed of an oxide having a NASICON crystal structure containing at least Li, Zr, and P, and the Li and the Zr have a mixing ratio of the Li ( 1 + 4x), since the blending ratio of Zr is expressed as (2-x) so that x is 0.1 to 0.4, the decrease in ionic conductivity is suppressed even at room temperature. The obtained solid electrolyte material can be obtained.

  The all solid state battery of the present invention is an all solid state battery having a positive electrode layer on one main surface of a solid electrolyte layer and a negative electrode layer on the other main surface of the solid electrolyte layer, Since the electrolyte layer is mainly composed of any of the solid electrolyte materials described above, an all-solid battery having good capacity characteristics and ensuring a desired large capacity without causing a decrease in ionic conductivity even at room temperature is obtained. It becomes possible.

It is sectional drawing which shows typically one Embodiment of the all-solid-state battery produced using the solid electrolyte material which concerns on this invention. It is a figure which shows the X-ray spectrum in 25 degreeC of each sample produced in the Example with a reference pattern. It is a figure which shows the discharge characteristic of the sample number 3. FIG.

  Next, an embodiment of the present invention will be described in detail.

  The solid electrolyte material as one embodiment of the present invention is formed of an oxide having a NASICON crystal structure containing at least Li, Zr, and P as a main component.

The NASICON crystal structure can be represented by the general formula AY ₂ (XO ₄ ) ₃ and has a structure in which the vertex of the regular octahedron YO _{6 and} the vertex of the regular tetrahedron XO ₄ are shared and arranged three-dimensionally. However, since the crystal structure has large voids and Li ions as the ion conductive substance A easily move, it is excellent as a medium for moving Li ions. In particular, among the NASICON type crystal structure, the phosphoric acid compound in which the polyanion of the regular tetrahedron XO ₄ is formed of PO ₄ can densely and integrally sinter the solid electrolyte and the electrode layer.

  In addition, since Zr has good resistance to reduction, the deterioration of the characteristics of the solid electrolyte layer can be suppressed even when used at a low potential by forming the central element Y with Zr and using it for the solid electrolyte layer. It is possible to suppress a decrease in ion conductivity due to the reduction of the electrolyte. Further, by using a solid electrolyte material containing Zr in the negative electrode layer or in the vicinity of the negative electrode layer, it is possible to avoid the reduction of the solid electrolyte layer at the potential of the negative electrode layer, and the charge / discharge characteristics of the all-solid battery. Can be prevented from being damaged.

  In the present solid electrolyte material, Li and Zr are referred to as x (hereinafter simply referred to as “x value”) when the mixing ratio of Li is (1 + 4x) and the mixing ratio of Zr is (2-x). ) Is 0.1 to 0.4.

  That is, the main component of the solid electrolyte material can be represented by the general formula (A).

Li _{1 + 4x} Zr _2-x (PO ₄ ) ₃ ... (A)

  Here, the x value satisfies Expression (1).

0.1 ≦ x ≦ 0.4 (1)

  Thus, when the general formula (A) satisfies the formula (1), the crystal system can be a rhombohedral single-phase structure even at room temperature (for example, 25 ° C.). It is possible to obtain a solid electrolyte material capable of suppressing a decrease in ion conductivity and capable of realizing an all-solid battery having desired capacity characteristics.

  That is, the ionic conductivity of the solid electrolyte material is affected by both the resistance caused by the crystal grain boundaries of the solid electrolyte and the resistance within the crystal particles of the solid electrolyte material. And, it is known that, in a phosphate compound having a Nasicon-type crystal structure in which Zr is a central element Y, ion conductivity is improved by making the crystal system a rhombohedral system.

However, even if it has a NASICON crystal structure, when the composition of the main component is formed of LiZr ₂ (PO ₄ ) ₃ (x = 0), the crystal system becomes triclinic at room temperature. It does not become rhombohedral, so that the ionic conductivity is lowered and the desired ionic conductivity cannot be ensured.

  On the other hand, when the x value exceeds 0.5, the crystal system becomes a mixed crystal system of rhombohedral and monoclinic systems, or becomes monoclinic and has a rhombohedral single phase at room temperature. It does not become a structure, and the ionic conductivity is lowered. In this case, it is difficult to obtain a desired ionic conductivity.

  On the other hand, when the x value is 0.1 to 0.4, the crystal system becomes a rhombohedral single-phase structure at room temperature (for example, 25 ° C.), and the crystal system is stabilized. Even if it exists, the fall of ion conductivity can be suppressed and desired favorable ion conductivity can be obtained.

  In particular, when the x value is 0.1 to 0.2, the crystal system is stabilized by the rhombohedral system, and the ion conductivity can be further improved.

  Therefore, in this embodiment, the x value is 0.1 to 0.4, preferably 0.1 to 0.2.

  It is also preferable to substitute a part of Zr with at least one element selected from Ca, Mg, Ba, Sr, Al, Sc, Y, In, Ti, Ge, Ga, and Hf. Thus, the temperature stability can be improved, the crystal system can be made a more stable rhombohedral single-phase structure, and thus a solid electrolyte material having stable ion conductivity can be obtained.

  FIG. 1 is a cross-sectional view schematically showing an embodiment of an all solid state battery according to the present invention.

  In this all-solid-state battery, a positive electrode current collector 2 is formed on one main surface of the laminated sintered body 1, and a negative electrode current collector 3 is formed on the other main surface of the laminated sintered body 1.

  The current collector material for forming the positive electrode current collector 2 and the negative electrode current collector 3 is particularly limited as long as it is a conductive material having good electron conductivity and good adhesion to the laminated sintered body 1. Instead, for example, Pt, Au, Ag, Al, Cu, stainless steel, ITO (indium tin oxide), or the like can be used.

  In the laminated sintered body 1, a positive electrode layer 5 joined to the positive electrode current collector 2 is formed on one main surface of the solid electrolyte layer 4, and a negative electrode current collector is formed on the other main surface of the solid electrolyte layer 4. A negative electrode layer 6 bonded to the body 3 is provided.

  The solid electrolyte layer 4 is mainly composed of the solid electrolyte material of the present invention. The positive electrode layer 5 contains a positive electrode active material, a solid electrolyte material, and a conductive agent, and the negative electrode layer 6 contains a negative electrode active material, a solid electrolyte material, and a conductive agent.

  The solid electrolyte material contained in the positive electrode layer 5 and the negative electrode layer 6 is not particularly limited, and the solid electrolyte material of the present invention described above may be used, and is different from the solid electrolyte material of the present invention. Materials may be used.

  When the solid electrolyte material of the present invention is used as the solid electrolyte material in the positive electrode layer 5 and the negative electrode layer 6, a solid electrolyte material that can be densely sintered at a firing temperature and can ensure good ion conductivity. Can be obtained.

On the other hand, since the positive electrode layer 5 has a higher potential than the negative electrode layer 6, there is little need to consider reduction resistance. Therefore, LiTi (PO ₄ ) ₃ , Li _1.2 Ti _1.8 Al _0.2 (PO ₄ ) _3, etc. It is also preferable to use a solid electrolyte material having a NASICON type crystal structure using Ti having good conductivity as a central metal.

Also, there are no particular restrictions on the positive electrode active material, for example, _{Li 3 V 2 (PO 4)} 3, LiFePO 4, phosphoric acid compounds such as _{LiMnPO 4, LiCoO 2, LiCo 1/3} Ni 1/3 Mn 1 _A compound having a spinel structure such as a cobalt compound such as _{/ 3} O ₂ and LiMnO ₄ or LiNi _0.5 Mn _1.5 O ₄ can be used alone or in combination.

The negative electrode active material is not particularly limited, and for example, Nb ₂ O ₅ , TiO ₂ , SiO, SnO, MoO ₂ , Cr ₂ O ₃ , Fe ₂ O ₃ , NiO, MnO, CoO, Cu ₂ O, CuO , WO, V ₂ O ₅ , RuO _{2 and the} like can be used alone or in combination.

  In addition, the conductive agent contained in the positive electrode layer 5 and the negative electrode layer 6 is not particularly limited. For example, carbonaceous fine particles such as graphite, carbon black, and acetylene black, vapor-grown carbon fibers, carbon nanotubes, Carbon fibers such as carbon nanohorn, conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, and polyacene can be used.

  Next, the manufacturing method of this all-solid-state battery is explained in full detail.

  First, a solid electrolyte material of the present invention, a binder resin such as a polyvinyl acetal resin, and an organic solvent such as ethanol are prepared, and weighed so that the solid electrolyte material, the binder resin, and the organic solvent have a predetermined weight ratio.

  Then, after dissolving the binder resin in an organic solvent to produce an organic vehicle, it is put into a ball mill together with a solid electrolyte material and a grinding medium such as PSZ (partially stabilized zirconia) balls, and sufficiently mixed and pulverized to obtain a solid electrolyte slurry. Is made.

  Next, a positive electrode active material, a conductive agent, and a solid electrolyte material are prepared, and a predetermined amount of these positive electrode active material, conductive agent, and solid electrolyte material is weighed to obtain a positive electrode material.

  Then, this positive electrode material is put into a pot mill together with the pulverization medium and the organic vehicle, and sufficiently mixed and pulverized to produce a positive electrode slurry.

  Next, a negative electrode active material, a conductive agent, and a solid electrolyte material are prepared, and a predetermined amount of these negative electrode active material, conductive agent, and solid electrolyte material is weighed to obtain a negative electrode material.

  Then, this negative electrode material is put into a pot mill together with the pulverization medium and the organic vehicle, and sufficiently mixed and pulverized to prepare a negative electrode slurry.

  Next, the solid electrolyte slurry, the positive electrode slurry, and the negative electrode slurry prepared as described above are applied onto a base film using a doctor blade method, a die coater method, a comma coater method, a screen printing method, and the like, and then formed. Processing is performed to produce a solid electrolyte layer green sheet, a positive electrode layer green sheet, and a negative electrode layer green sheet, each having a predetermined thickness.

  Next, the solid electrolyte layer green sheet, the positive electrode layer green sheet, and the negative electrode layer green sheet are respectively peeled from the base film, and the positive electrode layer green sheet, the solid electrolyte layer green sheet, and the negative electrode layer Laminate green sheets sequentially. And after thermocompression bonding at a predetermined pressure, it is sealed in a film container and pressurized using a hot isostatic press, a cold isostatic press, a hydrostatic press, etc., whereby a solid electrolyte layer green sheet is formed. A laminated structure sandwiched between the positive electrode layer green sheet and the negative electrode layer green sheet is prepared.

  Next, the laminated structure is subjected to a binder removal treatment at a predetermined temperature, and then subjected to a firing treatment, whereby the laminated sintered body 1 in which the positive electrode layer 5 and the negative electrode layer 6 are formed on both main surfaces of the solid electrolyte layer 4. Is made.

  Finally, a positive electrode current collector 2 and a negative electrode current collector 3 are formed on both main surfaces of the laminated sintered body 1 using a thin film forming method such as a sputtering method or a vacuum vapor deposition method, and then dried. After removing the adsorbed moisture from the atmosphere, it is sealed in a battery can, thereby producing an all-solid battery.

  Thus, this all solid state battery has the positive electrode layer 5 on one main surface of the solid electrolyte layer 4 and the negative electrode layer 6 on the other main surface of the solid electrolyte layer 4. Since the layer 6 contains the solid electrolyte material, it is possible to obtain an all-solid battery that can be densely sintered at the sintering temperature and that can secure even better ion conductivity.

  In addition, this invention is not limited to the said embodiment, A various deformation | transformation is possible in the range which does not deviate from a summary. For example, the solid electrolyte layer 4 only needs to have the solid electrolyte material of the present invention as a main component, and does not prevent the inclusion of a trace amount of additives, inevitable impurities, and the like.

  Moreover, in the said embodiment, although the solid electrolyte layer 4 is formed with the green sheet for one solid electrolyte layer, it is good also as a multilayered structure of two or more layers.

  In addition, the solid electrolyte slurry, the positive electrode slurry, and the negative electrode slurry are prepared using a ball mill in the above embodiment, but a viscomill method, a sand mill method, a high-pressure homogenizer method, a kneader dispersion method, or the like is used. May be. Moreover, you may add phthalic acid esters, such as dioctyl phthalate and diisononyl phthalate, as a plasticizer to each of these slurries.

  Next, examples of the present invention will be specifically described.

  Various solid electrolyte materials having different x values were prepared, and these samples were evaluated.

[Sample preparation]
Li ₂ CO ₃ , ZrO ₂ , and NH ₄ H ₂ PO ₄ were prepared as raw materials, and these raw materials were weighed in a predetermined amount so as to have a composition as shown in Table 1 after firing.

  Next, these weighed products were put into a polyethylene pot mill and mixed for 16 hours to obtain a mixed powder.

  And it heat-processed for 5 hours at the temperature of 700 degreeC in air | atmosphere, and removed the volatile component in raw material powder.

  Next, the raw material powder from which these volatile components have been removed is put into a polyethylene pot mill together with pure water and PSZ balls, and the pot mill is rotated at a rotation speed of 150 rpm for 16 hours, and then heated to 120 ° C. The dried water was removed by drying on the hot plate to obtain a dry powder.

Subsequently, this dry powder was pressurized at a pressure of 50 kN / cm ² to obtain a pellet-shaped molded body having a diameter of 10 mm and a thickness of 500 to 1000 μm.

  Next, this molded body was baked for 20 hours at a temperature of 1000 to 1200 ° C. in an air atmosphere to prepare samples Nos. 1 to 8.

  In addition, about each sample of sample numbers 1-8, when the volumetric shrinkage ratio before and behind sintering was calculated | required from the molded object volume before baking and the sintered compact volume after baking, it is shrinking around 30 vol% by volume ratio. It was confirmed.

(Sample evaluation)
About each sample of sample numbers 1-8, the X-ray-diffraction apparatus in the temperature of 25 degreeC was measured in the angle measurement range of 10 to 60 degrees at the scanning speed of 4.0 degrees / min using the X-ray-diffraction apparatus.

  FIG. 2 shows the X-ray diffraction spectrum of each sample together with a reference pattern. The horizontal axis represents the diffraction angle 2θ (°), and the vertical axis represents the X-ray intensity (au).

The reference pattern indicates a crystal system pattern of a JCPDS (Joint Committee on Power Diffraction Standards) card, and the reference pattern LZPt is a triclinic crystal pattern (No. 01-074-2562) of LiZr ₂ (PO ₄ ) ₃ , reference pattern LZPr is LiZr _{2 (PO 4) 3} of the rhombohedral pattern (No.01-084-0998), the reference pattern LZPm is LiZr _{2 (PO 4) 3} of the monoclinic pattern (Nanba01-070 -5819).

  As is apparent from FIG. 2, sample number 1 almost coincides with the reference pattern LZPt, and it was found that the crystal system was triclinic.

  Sample numbers 2 to 5 almost coincided with the reference pattern LZPr, and the crystal system was found to be rhombohedral.

  Sample No. 6 has a spectral pattern in which the reference pattern LZPr and the reference pattern LZPm are combined. Therefore, the crystal system is considered to be a mixed crystal system of rhombohedral system and monoclinic system.

  Sample Nos. 7 and 8 were almost identical to the reference pattern LZPm, and the crystal system was found to be monoclinic.

  Next, sputtering was performed on each sample of sample numbers 1 to 8 using Pt as a target material, and electrodes were formed on both main surfaces of each sample. Then, using an impedance analyzer (Agilent Technology 4294A), the impedance was measured under the conditions of a measurement frequency of 0.1 to 1 MHz and an amplitude of 100 mV at a temperature of 25 ° C., and the ionic conductivity was calculated from the measurement result. .

  Table 1 shows the component composition, crystal system, and ionic conductivity of sample numbers 1-8.

Sample No. 1 had a small ionic conductivity of 6.2 × 10 ⁻⁷ S / cm. This is probably because the x value was 0.0 and the crystal system was triclinic and did not have a rhombohedral single-phase structure.

Sample No. 6 had an ionic conductivity as small as 5.5 × 10 ⁻⁷ S / cm. This is probably because the x value was 0.5 and the crystal system was a rhombohedral and triclinic mixed crystal system and did not have a rhombohedral single-phase structure.

Sample No. 7 had a small ion conductivity of 4.3 × 10 ⁻⁸ S / cm. This is presumably because the x value was 0.7, the crystal system was monoclinic, and the rhombohedral single phase structure was not achieved.

Sample No. 8 had a small ion conductivity of 1.1 × 10 ⁻⁸ S / cm. This is probably because the x value was 1.0 and the crystal system was monoclinic as in sample number 7, and the rhombohedral single phase structure was not achieved.

On the other hand, Sample Nos. 2 to 5 have an x value of 0.1 to 0.4 within the range of the present invention, and the crystal system is a rhombohedral single-phase structure. It was found to be × 10 ^{−6 to} 5.1 × 10 ⁻⁶ S / cm, and good ionic conductivity of 1.0 × 10 ⁻⁶ S / cm or more was obtained even at 25 ° C.

In particular, by setting the x value to 0.1 to 0.2 as in sample numbers 2 and 3, the ionic conductivity is 4.7 × 10 ^{−6 to} 5.1 × 10 ⁻ even at 25 ° C. It was found that a better ionic conductivity of ⁶ S / cm can be obtained.

  As is clear from sample numbers 2 to 8 in Table 1, it was also found that the ionic conductivity decreases as the x value increases.

  All-solid batteries were fabricated and battery characteristics were evaluated.

(Preparation of green sheet for solid electrolyte layer)
First, sample number 3 (Li _1.8 Zr _1.8 (PO ₄ ) ₃ ) of Example 1 was prepared as a solid electrolyte material, a polyvinyl acetal resin as a binder resin, and ethanol as an organic solvent.

  And these solid electrolyte material, polyvinyl acetal resin, and ethanol were weighed so that it might become solid electrolyte material: polyvinyl acetal resin: ethanol = 100: 15: 140 by weight ratio.

  Next, after the polyvinyl acetal resin is dissolved in ethanol to prepare an organic vehicle, the organic vehicle is put into a ball mill together with the solid electrolyte material and the PSZ balls, mixed well, the PSZ balls are removed, and the solid electrolyte slurry is removed. Produced.

  Next, using the doctor blade method, each solid electrolyte slurry is coated on a polyethylene terephthalate (PET) film, dried on a hot plate heated to a temperature of 40 ° C., and molded to a thickness of 35 μm. Then, the length was cut into 25 mm and the width was cut into 25 mm, thereby producing a green sheet for a solid electrolyte layer on a PET film.

(Preparation of green sheet for positive electrode layer)
Li ₃ V ₂ (PO ₄ ) ₃ having a NASICON crystal structure as a positive electrode active material, carbon black as a conductive agent, and a solid electrolyte material of Example 1 and sample number 3 were prepared.

  Next, an organic vehicle was prepared in the same manner as described above so that the positive electrode active material, polyvinyl acetal resin and ethanol were in a weight ratio of positive electrode active material: polyvinyl acetal resin: ethanol = 100: 15: 140. The mixture was put into a pot mill together with the pulverizing medium and the organic vehicle, and sufficiently mixed and pulverized to prepare a positive electrode active material slurry.

  Next, after preparing an organic vehicle in the same manner as described above so that the conductive agent, polyvinyl acetal resin and ethanol are in a weight ratio of conductive agent: polyvinyl acetal resin: ethanol = 100: 15: 140, The mixture was put into a pot mill together with the pulverization medium and the organic vehicle, and sufficiently mixed and pulverized to prepare a conductive agent slurry.

  Next, the positive electrode active material slurry, the positive electrode active material slurry, so that the solid electrolyte slurry and the conductive agent slurry described above are positive electrode active material slurry: solid electrolyte slurry: conductive agent slurry = 40: 50: 10 by weight ratio, The solid electrolyte slurry and the conductive agent slurry were weighed, and these weighed materials were put into a pot mill together with the grinding medium and the organic vehicle, and sufficiently mixed and ground to produce a positive electrode slurry.

  Thereafter, using the same doctor blade method as described above, the positive electrode slurry was subjected to a molding process, and a positive electrode layer green sheet having a thickness of 35 μm was produced on a PET film.

(Preparation of negative electrode layer green sheet)
P _0.2 Nb _1.80 O ₅ as the negative electrode active material, carbon black as the conductive agent, and the solid electrolyte material of Example 1 and Sample No. 3 were prepared.

  Next, an organic vehicle was prepared in the same manner as described above so that the negative electrode active material, polyvinyl acetal resin, and ethanol were in a weight ratio of negative electrode material: polyvinyl acetal resin: ethanol = 100: 15: 140, and then the negative electrode material was pulverized. The medium and the organic vehicle were put together in a pot mill, and sufficiently mixed and pulverized to prepare a negative electrode active material slurry.

  Next, the above-described conductive agent slurry was prepared.

  Next, the negative electrode active material slurry, the solid electrolyte slurry and the conductive agent slurry described above are negative electrode active material slurry: solid electrolyte slurry: conductive agent slurry = 40: 50: 10 in a weight ratio, The solid electrolyte slurry and the conductive agent slurry were weighed, and these weighed materials were put into a pot mill together with the grinding medium and the organic vehicle, and sufficiently mixed and ground to prepare a negative electrode slurry.

  Thereafter, using the same doctor blade method as described above, the negative electrode slurry was subjected to molding processing, and a negative electrode layer green sheet having a thickness of 20 μm was produced on a PET film.

(Production of all-solid battery)
The solid electrolyte layer green sheet, the positive electrode layer green sheet, and the negative electrode layer green sheet are each peeled off from the PET film, and one positive electrode layer is formed on one main surface of the five solid electrolyte layer green sheets. A green sheet for the negative electrode layer was disposed on the other main surface of the green sheet for the solid electrolyte layer. This is sandwiched between two stainless steel plates heated to 60 ° C., thermocompression bonded at a pressure of 98 MPa (1000 kg / cm ² ), sealed in a polyethylene film container, and isotropically treated with a hydrostatic pressure of 180 MPa. The laminated structure in which the green sheet for positive electrode layers and the green sheet for negative electrode layers were respectively formed on both main surfaces of the green sheet for solid electrolytes was produced.

Next, this laminated structure was cut into a length of 10 mm and a width of 10 mm, sandwiched between two porous setters, and fired in a state of being pressurized at a pressure of 0.2 MPa (2 kg / cm ² ). That is, after performing a binder removal treatment at a temperature of 500 ° C. in a nitrogen atmosphere containing 1 vol% oxygen, a firing treatment is performed at a temperature of 900 ° C. for 2 hours in a nitrogen atmosphere. Produced.

  Next, sputtering was performed on the positive electrode and the negative electrode of the laminated sintered body using Pt as a target material, and a positive electrode current collector and a negative electrode current collector made of Pt were produced on both main surfaces of the laminated sintered body.

  Thereafter, this was dried at a temperature of 100 ° C. to remove moisture, and then sealed in a battery can having a diameter of 20 mm and a thickness of 3.2 mm, thereby preparing a sample of an all-solid battery.

(Sample characteristic evaluation)
The sample obtained as described above is placed in a thermostat kept at 25 ° C., charged to 3.25 V with a constant current of 15 μA corresponding to a current of about 0.1 C with respect to the weight of the positive electrode active material, After holding for 5 hours, it was rested for 3 hours, and then discharged to 0 V with a constant current of 15 μA, and then rested for 3 hours. This charge / discharge cycle was repeated twice, and the discharge capacity was measured after the second charge / discharge cycle was completed.

  FIG. 3 shows the measurement results. The horizontal axis is the discharge capacity (μAh), and the vertical axis is the voltage (V).

  As is clear from FIG. 3, the all solid state battery of the sample of the present invention has a discharge capacity of about 170 μAh even at 25 ° C., and it was confirmed that good capacity characteristics were obtained.

  Desirable good ion conductivity can be secured even at room temperature.

4 Solid electrolyte layer 5 Positive electrode layer 6 Negative electrode layer

Claims (8)

The main component is formed of an oxide having a NASICON crystal structure containing at least Li, Zr, and P;
The Li and the Zr are blended so that x is 0.1 to 0.4 when the blending ratio of the Li is (1 + 4x) and the blending ratio of the Zr is represented by (2-x). A solid electrolyte material characterized by that. _2. The solid electrolyte material according to claim 1, wherein the main component is represented by the general formula Li _{1 + 4x} Zr _2−x (PO ₄ ) ₃ (where 0.1 ≦ x ≦ 0.4). .   3. The solid electrolyte material according to claim 1, wherein x is 0.1 to 0.2.   A part of the Zr is substituted with at least one element selected from the names of Ca, Ba, Sr, Al, Sc, Y, In, and Hf. The solid electrolyte material according to any one of the above.   The solid electrolyte material according to any one of claims 1 to 4, wherein the crystal system has a rhombohedral single-phase structure. An all-solid battery having a positive electrode layer on one main surface of the solid electrolyte layer and a negative electrode layer on the other main surface of the solid electrolyte layer,
An all-solid-state battery, wherein the solid electrolyte layer is mainly composed of the solid electrolyte material according to any one of claims 1 to 5.   The all-solid-state battery according to claim 6, wherein at least one of the positive electrode layer and the negative electrode layer and the solid electrolyte layer are integrally sintered.   The all-solid-state battery according to claim 6, wherein at least one of the positive electrode layer and the negative electrode layer contains the solid electrolyte material.

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