JP6183783B2 - All solid battery - Google Patents

Description

  The present invention relates to an all-solid battery, and more particularly to an all-solid battery in which electrode layers are provided on both main surfaces of a solid electrolyte layer, and each of the solid electrolyte layer and the electrode layer contains a 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, a liquid electrolyte (electrolytic solution) mainly composed of an organic compound is usually used as a medium for transferring ions. 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 and development of secondary batteries using solid electrolytes instead of liquid electrolytes are being actively conducted today, and the electrolytes are made of solid electrolytes and other components are also made of solids. All-solid-state batteries are also being actively developed.

  For example, Patent Document 1 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 formed between the positive electrode layer and the negative electrode layer, and the positive electrode layer And an all-solid battery in which at least one of the negative electrode layers contains an oxide active material and a glassy sulfide solid electrolyte material having an interface resistance increase rate of 2 times or less before and after oxidation is proposed. Yes.

  That is, although the glassy sulfide has good ionic conductivity, when the glassy sulfide is used for the solid electrolyte material in the electrode layer, when it comes into contact with the oxide active material in the electrode layer under a high temperature atmosphere, The glassy sulfide is oxidized by heat, which may cause a decrease in ionic conductivity and increase internal resistance.

  Therefore, in Patent Document 1, a glassy sulfide solid electrolyte material having an interface resistance increase rate of 2 times or less before and after oxidation is included in the electrode layer, thereby suppressing deterioration of the solid electrolyte material. Trying to.

  Moreover, in this patent document 1, since glassy sulfide has favorable ion conductivity, it is used also for the solid electrolyte layer.

Further, Patent Document 2, the main phase _{Li X Si Y N 1/3 (X} + 4Y) ( however, X> 0, Y> 0 ) has a composition represented by, lithium silicon nitride sintered containing Ca Conjugation has been proposed.

  In this Patent Document 2, by substituting a part of Li with Ca, the activation energy is lowered, and thereby the ionic conductivity is prevented from being lowered even when the temperature is lowered from a high temperature state. .

  That is, in this patent document 2, the activation energy is changed by the amount of substitution of Ca, thereby controlling the ionic conductivity.

JP 2012-094446 A (Claim 1, paragraph numbers [0008], [0059], [0072], [0085], etc.) JP 2012-101981 (Claim 1, paragraph numbers [0001], [0014], [0042])

  By the way, in the all solid state battery, it is possible to ensure desired capacity characteristics even when used in a high temperature atmosphere by increasing the ionic conductivity in a high temperature range. On the other hand, by reducing the ionic conductivity near room temperature, self-discharge near the room temperature is reduced, so that good storage stability can be obtained. Furthermore, it is preferable to suppress variations in ion conductivity with respect to temperature fluctuations in the electrode layer, which can suppress variations in internal resistance of the electrode layer and suppress deterioration in battery characteristics.

  Therefore, in this type of all solid state battery, it is desirable to appropriately control the ionic conductivity with respect to temperature fluctuations.

  However, although Patent Document 1 suppresses a decrease in ionic conductivity in a high-temperature atmosphere, it does not control the ionic conductivity for temperature fluctuations, and thus ensures good storage stability near room temperature. It is difficult. In addition, as described above, since the ionic conductivity is not controlled with respect to the temperature variation, if the ionic conductivity variation occurs in the electrode layer due to the temperature variation, the internal resistance of the electrode layer also varies. For this reason, there is a risk of deteriorating characteristics.

  Further, Patent Document 2 controls ionic conductivity by the amount of substitution of Ca, thereby trying to suppress the ionic conductivity from being lowered even when the temperature is lowered from a high temperature state. The ion conductivity is not controlled with respect to temperature fluctuations, it is difficult to ensure good storage stability near room temperature, and the internal resistance of the electrode layer may vary, leading to characteristic deterioration. .

  The present invention has been made in view of such circumstances, and has good capacity characteristics that can secure a large capacity even when used in a high temperature atmosphere, and has good storage characteristics and suppresses deterioration of battery characteristics as much as possible. It is an object of the present invention to provide a sintered all solid state battery.

  It is known that the relationship between ionic conductivity and temperature depends on the Arrhenius equation.

  According to the Arrhenius equation described later, the ionic conductivity increases as the temperature increases and decreases as the temperature decreases. And when activation energy is large, the fluctuation | variation of the ionic conductivity with respect to a temperature difference also becomes large. Therefore, when such a solid electrolyte material having a large activation energy is used for the solid electrolyte layer, a higher ionic conductivity can be obtained in a high-temperature atmosphere, and a desired large-capacity all-solid battery can be obtained. . On the other hand, since the ionic conductivity is sufficiently small and self-discharge is reduced in a low-temperature atmosphere, it is possible to ensure good storage stability near room temperature.

Moreover, when activation energy is small, the fluctuation | variation of the ionic conductivity with respect to a temperature difference becomes small. Therefore, when such a solid electrolyte material having a small activation energy is used for an electrode layer , for example, a negative electrode layer , a change in ionic conductivity due to temperature fluctuation is also reduced, and variation in internal resistance in the electrode layer can be suppressed. It becomes possible to suppress deterioration of battery characteristics.

The present invention has been made on the basis of such knowledge. In the all solid state battery according to the present invention, the positive electrode layer and the negative electrode layer are provided on both main surfaces of the solid electrolyte layer, respectively . In addition, the negative electrode layer contains a second solid electrolyte material, and the first and second solid electrolyte materials have activation energy according to the Arrhenius plot and the first solid electrolyte material . solid the activation energy of the electrolyte material is characterized greater than the activation energy of the second solid electrolyte material.

  In the all solid state battery of the present invention, the activation energy of the first solid electrolyte material is preferably 50 kJ / mol or more.

  As a result, it becomes possible to obtain a large discharge capacity of 100 mAh / g or more, which has a further positive effect on storage stability, and has a desirable capacity characteristic even after being stored for a long time and having a desired capacity. An all-solid battery can be obtained.

  Furthermore, in the all solid state battery of the present invention, it is preferable that the activation energies of the first and second solid electrolyte materials are controlled by a crystal system in the same composition system.

  Thereby, the basic skeletons of the crystal structures of the first and second solid electrolyte materials are the same, and it is possible to ensure good interface bonding between the respective layers.

  In the all-solid-state battery of the present invention, the first solid electrolyte material mainly comprises a compound having a monoclinic crystal system or a triclinic crystal system, and the second solid electrolyte The material is preferably composed mainly of a compound having a rhombohedral system.

  Furthermore, in the all-solid-state battery of the present invention, it is more preferable that the first and second solid electrolyte materials have a basic skeleton of a crystal structure having a NASICON type structure.

  This makes it possible to easily move cations such as Li ions between the electrode layers.

  In the all solid state battery of the present invention, it is preferable that the first and second solid electrolyte materials include a phosphoric acid compound.

  In the all solid state battery of the present invention, the first solid electrolyte material is preferably a lithium-containing zirconium phosphate compound as a main component.

  In this case, in the lithium-containing zirconium phosphate compound, a part of the phosphorus element may be substituted with a silicon element.

Furthermore, in the all solid state battery of the present invention, the second solid electrolyte material has a main component of the general formula Li _x M1 _y M2 _z (PO ₄ ) ₃ (where M1 is selected from Ti, Ge, and Zr). Including at least one selected, and M2 includes at least one selected from Mg, Ca, Ba, Al, Cr, In, Sc, Y, and Hf). , Z preferably satisfy 0.5 ≦ x ≦ 4, 0.5 ≦ y ≦ 2, and 0 ≦ z ≦ 1.5, respectively.

In the all solid state battery of the present invention, the positive electrode layer contains the second solid electrolyte material, and the second solid electrolyte material contained in each of the positive electrode layer and the negative electrode layer is different from each other. preferable.

  Thereby, for example, the negative electrode layer contains the second solid electrolyte material giving priority to reduction resistance, and the positive electrode layer contains the second solid electrolyte material giving priority to ion conductivity, so that the desired charge can be obtained even at a low potential. It becomes possible to perform a discharge reaction.

According to the all solid state battery of the present invention, the positive electrode layer and the negative electrode layer are respectively provided on both main surfaces of the solid electrolyte layer, the first solid electrolyte material is contained in the solid electrolyte layer, and the first negative electrode layer contains the first solid electrolyte material. 2 of the solid electrolyte material is contained, the first and second solid electrolyte material, together with activated energy by Arrhenius plot, wherein the activation energy of the first solid electrolyte material, the second solid it is greater than the activation energy of the electrolyte material, while it is possible to obtain a greater ionic conductivity in a high temperature atmosphere, the ionic conductivity at low temperatures atmosphere becomes sufficiently small, at around room temperature can be less self-discharge It is possible to ensure good storage stability. Further, in the electrode layer, the change in ionic conductivity due to temperature fluctuation is also reduced, and variations in internal resistance can be suppressed, so that deterioration of battery characteristics can be suppressed.

  As described above, according to the present invention, it is possible to obtain an all-solid-state battery that has good capacity characteristics, a large capacity, good storage stability, and can suppress deterioration of battery characteristics.

It is sectional drawing which shows typically one Embodiment of the all-solid-state battery which concerns on this invention. It is a figure which shows typically the Arrhenius plot which shows the relationship between ion conductivity (sigma) and temperature T. FIG. It is the figure which showed the X-ray spectrum of solid electrolyte material A-F produced in the Example with the crystal | crystallization type | system | group reference pattern. It is a figure which shows the capacity | capacitance characteristic of each sample of sample numbers 1-5. It is a figure which shows the initial stage capacity characteristic of sample number 1, and the capacity | capacitance characteristic after 30 days. It is a figure which shows the initial capacity characteristic of the sample number 2, and the capacity | capacitance characteristic after 30 days. It is a figure which shows the initial capacity characteristic of sample number 3, and the capacity | capacitance characteristic after 30 days. It is a figure which shows the initial capacity characteristic of the sample number 4, and the capacity | capacitance characteristic after 30 days. It is a figure which shows the initial stage capacity | capacitance characteristic of the sample number 5, and the capacity | capacitance characteristic after 30 days.

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

  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, electrode layers, that is, a positive electrode layer 5 and a negative electrode layer 6 are provided on both main surfaces of the solid electrolyte layer 4.

  The solid electrolyte layer 4 contains at least a first solid electrolyte material, and the electrode layers 5 and 6 contain at least an active material (positive electrode active material or negative electrode active material), a second solid electrolyte material, and a conductive agent. doing.

  The first and second solid electrolyte materials are selected so that the activation energy of the first solid electrolyte material is larger than the activation energy of the second solid electrolyte material.

  As a result, the ionic conductivity is temperature controlled via activation energy, so it has good capacity characteristics that can secure a large capacity even when used in a high-temperature atmosphere, has good storage characteristics, and deteriorates battery characteristics. It is possible to obtain a sintered all-solid battery that can suppress as much as possible.

  That is, it is known that the relationship between the ionic conductivity σ and the temperature T depends on the Arrhenius equation shown by the equation (1).

  Here, A is a frequency factor, R is a gas constant (= 8.314 J / K · mol), and Ea is activation energy.

  When the mathematical expression (1) is expressed in a logarithmic display, the mathematical expression (2) is obtained.

  FIG. 2 is an Arrhenius plot showing the relationship between the ionic conductivity σ and the temperature T, where the horizontal axis represents 1 / T and the vertical axis represents lnσ. The slope -Ea / R of the diagram is like P and Q in the figure according to the magnitude of the activation energy Ea.

  That is, when the activation energy Ea is large, as shown in the diagram P, the ionic conductivity σ increases as the temperature T increases, and the ionic conductivity σ increases as the temperature T decreases. Get smaller. Therefore, when a solid electrolyte material (first solid electrolyte material) having a large activation energy Ea is used for the solid electrolyte layer 4, the ion conductivity is sufficiently large even when used in a high temperature atmosphere (for example, 100 ° C. or higher). Thus, it is possible to ensure good capacity characteristics having a large capacity. In addition, in this case, since the ionic conductivity σ decreases at low temperatures, self-discharge can be reduced in a low-temperature atmosphere, and storage stability is improved when storing near room temperature (around 25 ° C.), and storage is performed for a long time. After that, it is possible to ensure a sufficient capacity even after reuse.

  On the other hand, when the activation energy Ea is small, as shown in the diagram Q, the change in the ion conductivity σ is small even if the temperature fluctuates, and the variation in the ion conductivity σ with respect to the temperature change can be suppressed. Therefore, by using such a solid electrolyte material (second solid electrolyte material) having a small activation energy Ea for the electrode layers 5 and 6, variation in ionic conductivity σ associated with temperature fluctuation can be suppressed. Since variations in the internal resistance of the electrode layers 5 and 6 can be suppressed, characteristic deterioration of the electrode layers 5 and 6 can be suppressed.

  Thus, the materials having different activation energies Ea are used for the solid electrolyte layer 4 and the electrode layers 5 and 6, and the activation energy Ea of the first solid electrolyte material is greater than the activation energy Ea of the second solid electrolyte material. By selecting and using a larger material, it has good capacity characteristics that can secure a large capacity even when used in a high-temperature atmosphere, and has good storage stability even when stored near room temperature, resulting in deterioration of battery characteristics. A sintered all-solid battery that can be suppressed as much as possible can be obtained.

  The activation energy Ea of the first solid electrolyte material is not particularly limited as long as it is greater than the activation energy Ea of the second solid electrolyte material, but is preferably 50 kJ / mol or more.

  When the first solid electrolyte material has an activation energy of 50 kJ / mol or more, a large discharge capacity of 100 mAh / g or more can be secured in a high temperature atmosphere, and good capacity characteristics can be obtained. Moreover, since such a large discharge capacity can be obtained, it has a further positive effect on the storage stability, and can be used with a sufficiently large capacity when reused after storage for a long time. It becomes.

  The method for controlling the activation energy Ea of the first and second solid electrolyte materials is not particularly limited, but is preferably controlled by a crystal system in the same composition system. The ionic conductivity depends strongly on the crystal system. In the case of the same composition system, since the basic skeleton of the crystal structure is the same, it is possible to obtain a bonding interface with good adhesion between the solid electrolyte layer 4 and the electrode layers 5 and 6, and a good battery. Characteristics can be secured.

  As such a crystal system, a compound having a monoclinic system or a triclinic system can be preferably used for the first solid electrolyte material having a large activation energy Ea, and the second solid electrolyte can be used. As the material, a compound having a rhombohedral system can be preferably used.

  In addition, these crystal systems should just hold | maintain a desired crystal system in an actual use temperature range (for example, 25-200 degreeC), and it is accept | permitted that a crystal system changes in a high temperature range. For example, the first solid electrolyte material may be a triclinic crystal system or a monoclinic crystal system in the actual use temperature region, and in the high temperature region exceeding the actual use temperature region, these crystal systems may be rhombohedral. It may be transferred to a crystal system or the like.

  Moreover, as a composition system, a compound having a basic skeleton of a crystal structure having a NASICON structure can be preferably used.

The NASICON structure can be represented by the general formula Y ₂ (XO ₄ ) ₃ (Y: transition metal, X: P, S, Mo, W, etc.), and the apex of the regular octahedron YO ₆ and the regular tetrahedron XO ₄ A medium for moving cations because it has a three-dimensionally arranged structure that is shared with the apex, has large voids in the crystal structure, and cations such as Li ions move easily As excellent. In particular, among the NASICON structure, a phosphoric acid compound in which the polyanion of regular tetrahedron XO ₄ is formed of PO ₄ is preferable because the solid electrolyte 4 and the electrode layers 5 and 6 can be densely and integrally sintered.

Of the solid electrolyte materials having such a NASICON structure, the first solid electrolyte material is preferably a lithium-containing zirconium phosphate compound in which the central metal is formed of Zr having good reduction resistance. Triclinic LiZr ₂ (PO ₄ ) ₃ and monoclinic Li _1.3 Zr ₂ (P _0.9 Si _0.1 O ₄ ) ₃ are more preferable because they have an activation energy Ea of 50 kJ / mol or more.

  Further, as the second solid electrolyte material, a lithium-containing phosphoric acid compound whose main component is represented by the general formula (A) can be preferably used.

Li _x M1 _y M2 _z (PO ₄ ) ₃ (A)
Here, M1 includes at least one selected from Ti, Ge, and Zr, and M2 is selected from Mg, Ca, Ba, Al, Cr, In, Sc, Y, and Hf. Including at least one species.

  Moreover, it is preferable that x, y, z in the general formula (A) satisfy the following mathematical formulas (3) to (5).

0.5 ≦ x ≦ 4 (3)
0.5 ≦ y ≦ 2 (4)
0 ≦ z ≦ 1.5 (5)
Specifically, as the second solid electrolyte material, LiTi (PO ₄ ) ₃ , Li _1.2 Ti _1.8 Al _0.2 (PO ₄ ) ₃ , Li _1.2 Ti _1.2 Al _0.2 (PO ₄ ) ₃ , Li _1.5 Ge _1.5 Al _0.5 (PO ₄ ) ₃ , Li _1.2 Zr _1.9 Ca _0.1 (PO ₄ ) ₃ or the like can be used.

Of these second solid electrolyte materials, the negative electrode layer 6 needed to be electrochemically stable against the low potential of the negative electrode, and therefore contained Zr having good reduction resistance as a central element. It is more preferable to use a lithium-containing phosphate compound, such as Li _1.2 Zr _1.9 Ca _0.1 (PO ₄ ) ₃ . On the other hand, the positive electrode layer 5 does not have such a restriction, and it is preferable to give priority to ionic conductivity. Therefore, LiTi (PO ₄ ) _{3 and} Li _1.2 Al _0.2 Ti containing Ti having a good ionic conductivity as a central element. _1.8 (PO ₄ ) ₃ or the like can be preferably used.

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

First, a first solid electrolyte material having a Nasicon type structure such as LiZr ₂ (PO ₄ ) ₃ having an activation energy Ea of preferably 50 kJ / mol or more, a binder resin such as polyvinyl acetal resin, and an organic solvent such as ethanol. Prepared and weighed so that these first solid electrolyte material, binder resin, and organic solvent have a predetermined weight ratio.

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

  Next, a positive electrode active material, a conductive agent, and an activation energy Ea are smaller than those of the first solid electrolyte material, preferably a second solid electrolyte material having a NASICON type structure containing Ti in the central metal is prepared, A predetermined amount of these positive electrode active material, conductive agent, and second solid electrolyte material are weighed to obtain a positive electrode material.

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

Here, the positive electrode active material is not particularly limited. For example, phosphoric acid compounds such as Li ₃ V ₂ (PO ₄ ) ₃ , LiFePO ₄ , LiMnPO ₄ , LiCoO ₂ , LiCo _1/3 Ni _1/3. Cobalt compounds such as Mn _1/3 O ₂ and spinel type compounds such as LiMnO ₄ and LiNi _0.5 Mn _1.5 O ₄ can be used alone or in combination.

  In addition, the conductive agent is not particularly limited, for example, carbonaceous fine particles such as graphite, carbon black, acetylene black, carbon fibers such as vapor grown carbon fiber, carbon nanotube, carbon nanohorn, polyaniline, polypyrrole, Conductive polymers such as polythiophene, polyacetylene, and polyacene can be used.

  Next, a second solid electrolyte material having a negative active material, a conductive agent, and an activation energy Ea smaller than that of the first solid electrolyte material, and preferably having a NASICON type structure containing Zr in the central metal is prepared. A predetermined amount of these negative electrode active material, conductive agent, and second solid electrolyte material is weighed to obtain a negative electrode material.

Here, the negative electrode active material is not particularly limited. 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, as a electrically conductive agent, the thing similar to what was used with the positive electrode material can be used.

  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 processed. 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 After sequentially laminating a predetermined number of green sheets, thermocompression bonded at a predetermined pressure, sealed in a film container, and pressurized by a method such as hot isostatic pressing, cold isostatic pressing, hydrostatic pressing, etc. A laminated structure in which the solid electrolyte layer green sheet is sandwiched between the positive electrode layer green sheet and the negative electrode layer green sheet is prepared.

  Next, the laminated structure is degreased at a predetermined temperature and then subjected to a firing treatment, thereby producing a 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 4.

  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.

  As described above, in the present embodiment, the electrode layers 5 and 6 are provided on both main surfaces of the solid electrolyte layer 4, the first solid electrolyte material is contained in the solid electrolyte layer 4, and the electrode layers 5 and 6 are included in the electrode layers 5 and 6. Since the second solid electrolyte material is contained and the activation energy of the first solid electrolyte material is larger than the activation energy of the second solid electrolyte material, it is possible to obtain higher ionic conductivity in a high temperature atmosphere. On the other hand, ionic conductivity is sufficiently small in a low-temperature atmosphere, and self-discharge is also reduced, so that it is possible to ensure good storage stability near room temperature. Further, in the electrode layer, the change in ionic conductivity due to temperature fluctuation is also reduced, and variations in internal resistance can be suppressed, so that deterioration of battery characteristics can be suppressed.

  In addition, by setting the activation energy Ea of the first solid electrolyte material to 50 kJ / mol or more, it becomes possible to obtain a large discharge capacity of 100 mAh / g or more, which has a further positive effect on storage. An all-solid battery having a desired capacity and good capacity characteristics can be obtained even after reuse for a long time after storage.

  Further, the activation energies of the first and second solid electrolyte materials are controlled by the crystal system in the same composition system, so that the basic skeletons of the crystal structures of the first and second solid electrolyte materials are the same. Thus, it is possible to ensure good interface bonding between the respective layers.

  Furthermore, the first and second solid electrolyte materials can easily move cations such as Li ions between the electrode layers 5 and 6 because the basic skeleton of the crystal structure has a NASICON structure. .

  Further, the positive electrode layer 5 and the negative electrode layer 6 contain different second solid electrolyte materials, so that the negative electrode layer 6 uses a second solid electrolyte material containing Zr having good reduction resistance. The layer 5 can be made of a second solid electrolyte material containing Ti having good ion conductivity, and a desired charge / discharge reaction can be performed even at a low potential.

  As described above, according to the present invention, it is possible to obtain an all-solid-state battery that has good capacity characteristics, has a large capacity, has good storage stability, and can suppress deterioration of battery characteristics.

  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, in the above-described embodiment, the solid electrolyte layer 4 is formed of a single green sheet for a solid electrolyte layer, but may have a multilayer structure of two or more layers. In this case, the solid electrolyte layer 4 is contained in the electrode layers 5 and 6. A plurality of types of first solid electrolyte materials having different activation energies may be combined as long as the activation energy is larger than the activation energy of the second solid electrolyte layer.

  Moreover, you may use the mixed powder of a multiple types of material type also about the 1st and 2nd solid electrolyte material contained in the solid electrolyte layer 4 and the electrode layers 5 and 6, respectively.

  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.

<Evaluation of solid electrolyte material>
[Production of solid electrolyte material]
As raw materials, Li ₂ O ₃ , ZrO ₂ , CaCO ₃ , Al ₂ O ₃ , TiO ₂ , Ge ₂ O ₃ , SiO ₂ and NH ₄ H ₂ PO ₄ are prepared, and these raw materials are sintered. A predetermined amount was weighed so as to have the composition shown in Table 1.

  Next, these weighed materials are put into a polyethylene pot mill, mixed for 16 hours to obtain a mixed powder, then heat-treated at a temperature of 500 ° C. in an air atmosphere, further heat-treated at 800 ° C., and volatilized. Components were removed to obtain a raw material powder.

  Next, this raw material powder was put into a pot mill together with pure water and PSZ balls, pulverized for 16 hours, and then dried to remove moisture to obtain a dry powder.

  Subsequently, this dry powder was heat-treated at a temperature of 1200 ° C. in an air atmosphere, thereby producing solid electrolyte materials A to F.

  Next, polyvinyl acetal resin was prepared as the binder resin, and ethanol was prepared as the organic solvent.

  Then, the solid electrolyte material, the polyvinyl acetal resin, and ethanol were weighed so that the weight ratio of solid electrolyte material: polyvinyl acetal resin: ethanol = 100: 15: 140.

  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 a doctor blade method, a 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, The solid electrolyte green sheet was produced by cutting into 25 mm length and 25 mm width.

Next, the solid electrolyte green sheet was peeled from the PET film, and 10 sheets of the solid electrolyte green sheet were laminated. This was 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 pressurized with a 180 MPa hydrostatic press. Thus, a solid electrolyte laminate was produced.

Next, this solid electrolyte laminate 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 degreasing process at a temperature of 500 ° C. in a nitrogen atmosphere containing 1 vol% oxygen, a baking process is performed at a temperature of 900 ° C. for 2 hours in a nitrogen atmosphere, and the solid electrolyte materials A to F are sintered. A ligature was prepared.

[Identification of crystal system]
Solid electrolyte materials A to F as sintered bodies are put into a container made of Pt, and an angle measurement of 10 ° to 60 ° is performed at a scanning speed of 1.0 ° / min at room temperature using an X-ray diffractometer. X-ray spectra were measured over the range.

  FIG. 3 shows X-ray diffraction spectra of the solid electrolyte materials A to F together with reference patterns A ′ to F ′. The horizontal axis represents the diffraction angle 2θ (°), and the vertical axis represents the X-ray intensity (au).

Reference patterns A ′ to F ′ are crystal patterns of JCPDS (Joint Committee on Power Diffraction Standards) cards, and reference pattern A ′ is LiZr ₂ (PO ₄ ) ₃ (hereinafter referred to as “LZP”). The triclinic pattern (No. 01-074-2562) and the reference pattern B ′ are Li _1.3 Zr ₂ (P _0.9 Si _0.1 O ₄ ) ₃ (hereinafter referred to as “LZPS”) monoclinic pattern (No. .01-070-5819), the reference pattern C ′ is a monoclinic pattern (No. 01-070-5819) of Li _1.1 Zr _1.9 Al _0.1 (PO ₄ ) ₃ (hereinafter referred to as “LZAP”), reference pattern D 'is _{Li 1.2 Zr 1.9 Ca 0.1 (PO} 4) 3 (( hereinafter, referred to as "LZCP".) rhombohedral pattern (Nanba01-072-7742), the reference pattern E' is L _{1.2 Ti 1.9 Al 0.1 (PO 4} ) 3 ( hereinafter, referred to as "LTAP".) Rhombohedral pattern (Nanba01-072-6140), the reference pattern F 'is _{Li 1.5 Ge 1.5 Al 0.5 (PO} 4) ₃ (hereinafter referred to as “LGAP”) rhombohedral pattern (No. 01-080-1922).

  As is apparent from FIG. 3, the crystal system of the solid electrolyte material A substantially matches the triclinic pattern (reference pattern A ′) of LZP, and the crystal system of the solid electrolyte material A is triclinic. Was identified.

  Further, the crystal system of the solid electrolyte material B substantially coincides with the monoclinic pattern (reference pattern B ′) of LZPS, and the crystal system of the solid electrolyte material B was identified as the monoclinic system.

  Furthermore, the crystal system of the solid electrolyte material C substantially coincides with the monoclinic pattern (reference pattern C ′) of LZAP, and the crystal system of the solid electrolyte material C was identified as being monoclinic.

  Similarly, the crystal systems of the solid electrolyte materials D to F substantially match the rhombohedral pattern of LZCP, LTAP, and LGAP, respectively. The crystal systems of these solid electrolyte materials D to F are rhombohedral. Identified.

[Measurement of activation energy]
Sputtering was performed on both principal surfaces of the sintered bodies of the solid electrolyte materials A to F using Pt as a target substance, thereby forming a pair of electrode layers. And after drying this at 100 degreeC and removing the water | moisture content adsorb | sucked from atmosphere, it enclosed in the battery can of diameter 20mm and thickness 3.2mm.

  And about each sample of these solid electrolyte materials A-F, it arrange | positions to the thermostat kept at each temperature of 20-100 degreeC, and uses an impedance analyzer (The Solartron company make, 1255B), Measurement frequency 0.1-1MHz The impedance Z was measured by applying a voltage of 100 mV. Next, the ion conductivity σ (S / cm), which is the reciprocal of the impedance Z, and the temperature T (K) are plotted on a graph of lnσ to 1 / T, and the slope −Ea / R (R = 8.314 J / K). The activation energy Ea was determined from mol).

  Table 1 shows the composition, crystal system, and activation energy Ea of the solid electrolyte materials A to F.

  Sample numbers A to F are all phosphoric acid compounds having a NASICON structure and have the same composition, but it was found that the activation energy Ea can be controlled by different crystal systems.

<Evaluation of all solid state battery>
[Production of all-solid-state batteries]
(Preparation of green sheet for solid electrolyte layer)
First, solid electrolyte materials A to D and F were prepared, polyvinyl acetal resin as a binder resin, and ethanol as an organic solvent.

  Subsequently, these solid electrolyte materials, polyvinyl acetal resin, and ethanol were weighed so that the first solid electrolyte material: polyvinyl acetal resin: ethanol = 100: 15: 140 by weight ratio.

  Then, after dissolving polyvinyl acetal resin in ethanol to prepare an organic vehicle, the organic vehicle is put into a ball mill together with the first solid electrolyte material and the PSZ ball, mixed well, the PSZ ball is removed, and the sample Solid electrolyte slurries with numbers 1 to 5 were prepared.

  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. The sample was cut into a length of 25 mm and a width of 25 mm, thereby producing green sheets for solid electrolyte layers of sample numbers 1 to 5.

(Preparation of green sheet for positive electrode layer)
Li ₃ V ₂ (PO ₄ ) ₃ was prepared as a positive electrode active material, acetylene black, and solid electrolyte materials E and F were prepared as conductive agents.

  Next, these positive electrode active material, conductive agent, and solid electrolyte material were weighed so that the weight ratio of positive electrode active material: conductive agent: solid electrolyte material = 40: 10: 50 was used as the positive electrode material.

  Then, after preparing the organic vehicle in the same manner as described above so that the positive electrode material, the polyvinyl acetal resin, and ethanol are in the weight ratio of positive electrode material: polyvinyl acetal resin: ethanol = 100: 15: 140, the positive electrode material is pulverized into the medium. And it put into the pot mill with the said organic vehicle, fully mixed and grind | pulverized, and produced the positive electrode slurry of the sample numbers 1-5.

  Thereafter, using the same doctor blade method as described above, the positive electrode slurry of Sample Nos. 1 to 5 was subjected to a molding process to produce a positive electrode layer green sheet having a thickness of 35 μm.

(Preparation of negative electrode layer green sheet)
Nb ₂ O ₅ was prepared as the negative electrode active material, acetylene black, and solid electrolyte materials D and F were prepared as the conductive agent.

  Next, the negative electrode active material, the conductive agent, and the solid electrolyte material were weighed so that the negative electrode active material: conductive agent: solid electrolyte material = 40: 10: 50 by weight ratio, and this was used as the negative electrode material.

  And after preparing an organic vehicle so that a negative electrode material, polyvinyl acetal resin, and ethanol may become positive electrode material: polyvinyl acetal resin: ethanol = 100: 15: 140 by weight ratio, the said negative electrode material is grind | pulverized as above-mentioned. And it put into the pot mill with the said organic vehicle, fully mixed and grind | pulverized, and produced the negative electrode slurry of the sample numbers 1-5.

  Thereafter, using the same doctor blade method as described above, the negative electrode slurry of Sample Nos. 1 to 5 was subjected to a molding process, and negative electrode layer green sheets of Sample Nos. 1 to 5 having a thickness of 20 μm were produced.

(Production of laminated sintered body)
Next, the solid electrolyte layer green sheet, the positive electrode layer green sheet, and the negative electrode layer green sheet are peeled off from the PET film, respectively, and five positive electrode layer green sheets are formed on one positive electrode layer green sheet. A green sheet and one green sheet for a negative electrode layer were sequentially laminated. This was 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 pressurized at a hydrostatic pressure of 180 MPa. Pressurized with a press, thereby producing a laminated structure in which the solid electrolyte layer green sheet was sandwiched between the positive electrode layer green sheet and the negative electrode layer green sheet.

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 degreasing process at a temperature of 500 ° C. in a nitrogen atmosphere containing 1 vol% oxygen, a baking process was performed at a temperature of 900 ° C. for 2 hours in a nitrogen atmosphere. A laminated sintered body was produced.

(Completion of all-solid battery)
Sputtering is performed on the laminated sintered body using Pt as a target material, and a positive electrode current collector and a negative electrode current collector are formed on both main surfaces of the laminated sintered body, respectively, and then dried at 100 ° C. from the atmosphere. After removing the adsorbed water, it was sealed in a battery can having a diameter of 20 mm and a thickness of 3.2 mm, thereby producing all-solid batteries of sample numbers 1 to 5.

[All-solid battery evaluation]
(Measurement of capacitance characteristics)
Each sample of sample numbers 1 to 5 was placed in a thermostatic bath maintained at 100 ° C. The battery is charged with a constant current of 40 μA until it reaches a voltage of 3.25 V, held at this 3.25 V for 5 hours, then rested for 3 hours, and then discharged with a constant current of 40 μA until the voltage becomes 0 V. The capacity characteristics were measured after a pause. A current of 40 μA corresponds to a current of about 0.1 C with respect to the weight of the positive electrode active material (1 C is a current amount at which charging or discharging is completed in one hour).

(Room temperature storage)
Each sample of sample numbers 1 to 5 was placed in a thermostatic bath maintained at 100 ° C. The battery is charged with a constant current of 40 μA until it reaches a voltage of 3.25 V, held at this 3.25 V for 5 hours, then rested for 3 hours, and then discharged with a constant current of 40 μA until the voltage becomes 0 V. The initial capacity characteristics at 100 ° C. were measured after a time rest.

  After that, the battery is charged again with a constant current of 40 μA until it reaches a voltage of 3.25 V, held at this 3.25 V for 5 hours, then maintained in a charged state, the temperature of the thermostat is adjusted to 25 ° C., and the thermostat Stored for 30 days. And after storage, the thermostat was again adjusted to 100 ° C., discharged at a constant current of 40 μA until the voltage became 0 V, paused for 3 hours, and the capacity characteristics after 30 days at 100 ° C. were measured.

  And based on Numerical formula (6), capacity | capacitance retention rate (eta) was computed from the initial stage capacity | capacitance C1 in 100 degreeC, and the capacity | capacitance C2 after 30 days.

η = C2 / C1 × 100 (6)
(Evaluation of measurement results)
Table 2 shows each composition of the positive electrode layer, the solid electrolyte layer, and the negative electrode layer, the discharge capacity, and the capacity retention rate of each sample of sample numbers 1 to 5.

  FIG. 4 shows the capacity characteristics at 100 ° C. of the samples of sample numbers 1 to 5. The horizontal axis is capacity (mAh / g), the vertical axis is voltage (V), sample numbers 1 to 3 indicated by solid lines are the present invention samples, and sample numbers 4 and 5 indicated by broken lines are the samples outside the present invention. .

  As apparent from Table 2 and FIG. 4, in Sample No. 4, the solid electrolyte material contained in the solid electrolyte layer and the solid electrolyte material contained in the negative electrode layer are formed of the same material. Since the activation energy was the same between the solid electrolyte material and the second solid electrolyte material, the discharge capacity was as low as 86 mAh / g.

  In Sample No. 5, the solid electrolyte material contained in the solid electrolyte layer and the solid electrolyte material contained in the positive electrode layer and the negative electrode layer are all formed of the same material. Since the activation energy was the same between the solid electrolyte material and the second solid electrolyte material, the discharge capacity was as low as 84 mAh / g.

  In contrast, in Sample Nos. 1 to 3, the activation energy Ea of the solid electrolyte material (first solid electrolyte material) contained in the solid electrolyte layer is contained in the electrode layers (positive electrode layer and negative electrode layer). It was larger than the activation energy Ea of the solid electrolyte material (second solid electrolyte material), and as a result, a good result was obtained with a discharge capacity of 100 mAh / g or more.

  5-9 show the initial capacity characteristics and the capacity characteristics after 30 days of Sample Nos. 1-5. 5 shows sample number 1, FIG. 6 shows sample number 2, FIG. 7 shows sample number 3, FIG. 8 shows sample number 4, and FIG. 9 shows initial capacity characteristics and sample capacity characteristics after 30 days. Yes. The horizontal axis represents capacity (mAh / g), and the vertical axis represents voltage (V).

  In sample No. 4, the second solid electrolyte material contained in the negative electrode layer is formed of the same material as the first solid electrolyte material contained in the solid electrolyte layer, and the second solid electrolyte material is activated. Since the energy Ea is too large, as shown in FIG. 8, the discharge capacity was initially 86 mAh / g, but after 30 days it was about 60 mAh / g, the capacity retention decreased to 70%, and the storage stability It was found that the battery characteristics deteriorated.

  In Sample No. 5, the second solid electrolyte material contained in the positive electrode layer and the negative electrode layer is formed of the same material as the first solid electrolyte material contained in the solid electrolyte layer. As in Sample No. 4, the activation energy Ea of the second solid electrolyte material is too large as shown in Sample No. 4, so the discharge capacity was 84 mAh / g at the beginning, but after about 30 days, it became about 54 mAh / g. It was found that the capacity retention rate was reduced to 64%, the storage stability was poor, and the battery characteristics were deteriorated.

  In contrast, in Sample Nos. 1 to 3, the activation energy Ea of the second solid electrolyte material contained in the electrode layers (positive electrode layer and negative electrode layer) is the first solid electrolyte contained in the solid electrolyte layer. It is smaller than the activation energy Ea of the material, it is possible to secure a discharge capacity of 97 mAh / g or more even after 30 days, a capacity retention rate of 87% or more, and it is found that the storage property is good and the deterioration of the battery characteristics can be suppressed. It was.

  By controlling the ionic conductivity, it is possible to obtain a large capacity even when used in a high-temperature atmosphere, and it has good storage stability even when stored at room temperature. It is possible to realize a sintered all solid state battery capable of suppressing the above.

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

Claims (10)

The positive electrode layer and negative electrode layer are provided on both main surfaces of the solid electrolyte layer,
The solid electrolyte layer contains a first solid electrolyte material, and the negative electrode layer contains a second solid electrolyte material,
The first and second solid electrolyte materials have activation energy according to an Arrhenius plot,
Wherein the activation energy of the first solid electrolyte material, all solid state battery and greater than the activation energy of the second solid electrolyte material.   2. The all solid state battery according to claim 1, wherein the activation energy of the first solid electrolyte material is 50 kJ / mol or more.   3. The all solid state battery according to claim 1, wherein the activation energies of the first and second solid electrolyte materials are controlled by a crystal system in the same composition system. The first solid electrolyte material is mainly composed of a compound having a crystal system of either monoclinic system or triclinic system,
The all-solid-state battery according to any one of claims 1 to 3, wherein the second solid electrolyte material is mainly composed of a compound having a rhombohedral system.   5. The all-solid-state battery according to claim 1, wherein the first and second solid electrolyte materials have a basic skeleton of a crystal structure having a NASICON structure.   6. The all-solid-state battery according to claim 1, wherein the first and second solid electrolyte materials include a phosphoric acid compound.   The all-solid-state battery according to claim 5 or 6, wherein the first solid electrolyte material is composed mainly of a lithium-containing zirconium phosphate compound.   8. The all-solid-state battery according to claim 7, wherein in the lithium-containing zirconium phosphate-based compound, part of the phosphorus element is substituted with a silicon element. It said second solid electrolyte material, the main component is the general formula _{Li x M1 y M2 z (PO} 4) 3 ( however, M1 comprises Ti, Ge, and at least one selected from among Zr, M2 is , Mg, Ca, Ba, Al, Cr, In, Sc, Y, and Hf.).
X, y, z are 0.5 ≦ x ≦ 4,
0.5 ≦ y ≦ 2,
0 ≦ z ≦ 1.5
The all-solid-state battery according to any one of claims 6 to 8, wherein the all-solid battery is satisfied. Wherein with the positive electrode layer contains the second solid electrolyte material, the positive electrode layer and the claims 1 to wherein said contained in each of the negative electrode layer a second solid electrolyte material and being different from each other 9 All-solid-state battery in any one of.

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