JP6666641B2 - All-solid secondary battery and method for manufacturing all-solid secondary battery - Google Patents

Description

  The present invention relates to an all-solid secondary battery using a nickel-containing transition metal oxide as a positive electrode active material.

  Conventionally, in an all-solid secondary battery using a compound having a layered rock salt structure as a positive electrode active material, when a battery reaction is performed in an atmosphere in which carbon dioxide or oxygen is present, a resistance component is generated at an interface between the positive electrode active material and the solid electrolyte. This causes a problem that the resistance of the battery is increased.

  Lithium nickelate as a positive electrode active material having a layered rock salt structure is noted for its high discharge capacity. However, lithium nickelate is chemically unstable, and therefore, in many cases, a part of nickel is replaced with another transition metal for use in batteries. Such a transition metal oxide can be generally synthesized by reacting lithium carbonate, lithium hydroxide, and a compound serving as a transition metal source. In this synthesis method, unreacted lithium hydroxide adheres to the surface of the product because lithium hydroxide is excessively added. That is, conventionally, the positive electrode active material is used in a state where lithium hydroxide is attached to the surface.

  Carbon dioxide and oxygen exist in the battery structure of the all-solid secondary battery. Therefore, lithium hydroxide adhering to the positive electrode active material reacts with carbon dioxide or the like, so that lithium carbonate is generated on the surface of the positive electrode active material. Lithium carbonate becomes a resistance component at the interface between the positive electrode active material and the solid electrolyte, and suppresses the discharge capacity of the secondary battery.

  That is, a transition metal oxide in which a part of lithium nickelate is replaced with a transition metal is a positive electrode active material that can be expected to have a stable and high capacity, but an interface resistance is easily generated at an interface with a solid electrolyte. . Therefore, when a transition metal oxide is used as the positive electrode active material, it is an issue to suppress the generation amount of the resistance component and improve the discharge capacity.

  In order to solve the above problems, a method for manufacturing an all-solid secondary battery in a regenerated argon atmosphere has been proposed (Patent Document 1). However, production in a regenerated argon atmosphere is not suitable for large-scale cell production or mass production because of the high capital investment costs. In addition, a solid-state battery element vacuum-sealed in a laminate film is proposed (Patent Document 2). However, the type and surface state of the positive electrode active material serving as a core for obtaining high energy have not been clarified, and it is expected that industrial production will be difficult.

JP 08-167425 A JP 2010-033937 A

  However, it is required to suppress the generation of lithium carbonate inside the battery structure and reflect the discharge capacity inherently provided in the positive electrode active material in the battery performance. An object of the present invention is to improve the function of lithium nickelate as a positive electrode active material by eliminating the cause of lithium carbonate generation, thereby providing an all-solid secondary battery having a high energy density.

The present invention provides, in a package, a positive electrode containing a transition metal oxide represented by the following formula (1) as a positive electrode active material, a negative electrode, and a solid electrolyte layer present between the positive electrode and the negative electrode. This is an all-solid-state secondary battery in which the total partial pressure of carbon dioxide and oxygen in the body is 200 Pa or less. In the formula (1), M is one or more elements selected from the group consisting of Co, Mn, Al and Mg. x, y, and z are values that satisfy all of 0.5 <x <1.2, 0.5 <y, 0 <z, and z = 1−y.

  Accordingly, in the present invention, the generation of lithium carbonate on the surface of the positive electrode active material during charge and discharge can be suppressed, and the electric resistance is suppressed.

  In the present invention, the total of the partial pressures of carbon dioxide and oxygen can be reduced to 200 Pa or less by replacing carbon dioxide and oxygen in the exterior body with an inert gas. The inert gas used is preferably at least one gas selected from the group consisting of helium, nitrogen, neon, argon, krypton, and xenon. In the case where carbon dioxide and oxygen in the exterior body are replaced with an inert gas, it is advantageous from the viewpoint of simplifying the process of reducing the total partial pressure of carbon dioxide and oxygen.

  The solid electrolyte constituting the solid electrolyte layer of the present invention contains sulfur (S) as the first element, lithium (Li) as the second element, and silicon (Si) and boron (B) as the third element. And at least one element selected from the group consisting of phosphorus (P). Since the above-mentioned solid electrolyte has high ionic conductivity, it contributes to the improvement of the energy density of the present invention.

  The present invention relates to an entirety comprising a cathode including a transition metal oxide represented by the formula (1) as a cathode active material, an anode, and a solid electrolyte layer disposed between the cathode and the anode in an exterior body. The present invention also encompasses a method for manufacturing an all-solid secondary battery including a step of reducing the partial pressure of carbon dioxide and oxygen present in an outer package of the solid secondary battery.

  The step of reducing the partial pressure of carbon dioxide and oxygen is performed until the total partial pressure of carbon dioxide and oxygen in the exterior body of the all solid state secondary battery becomes 200 Pa or less. Thereby, the abundance of carbon dioxide and the like in the battery structure of the all solid state secondary battery can be reduced. As a result, it is possible to suppress the amount of lithium carbonate that is a resistance component. In the step of reducing the partial pressure of carbon dioxide and oxygen, the outer casing may be evacuated, or the step of reducing the partial pressure of carbon dioxide and oxygen in the outer casing may be performed by inactivating the carbon dioxide and oxygen in the outer casing. It may be performed by replacing with a gas.

  The present invention can improve the energy density of an all-solid secondary battery using lithium nickelate as a positive electrode active material.

1 is a schematic plan view showing an example of an all solid state secondary battery of the present invention. FIG. 1 is a schematic sectional view showing an example of an all solid state secondary battery of the present invention. 9 is a measurement result of an IR spectrum obtained by measuring the abundance of lithium carbonate in an outer package after a battery reaction of the all solid state secondary battery of the present invention.

[All-solid secondary battery]
The all-solid-state secondary battery of the present invention has a structure in which a positive electrode, a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode are provided in an outer package. FIG. 1 is a schematic plan view of an example of an all solid state secondary battery of the present invention, and FIG. 2 is a schematic sectional view of an example of an all solid state secondary battery of the present invention. 1 and 2, 100 is an all solid state secondary battery, 201 is a positive electrode, 202 is a current collector, 301 is a negative electrode, 302 is a current collector, 400 is a solid electrolyte layer, and 500 is an exterior body.

[Positive electrode]
The positive electrode constituting the present invention contains at least a positive electrode active material, a solid electrolyte, a conductive agent, and a binder. As the positive electrode active material, a transition metal oxide represented by the following formula (1) is used. In the following formula (1), M is one or more elements selected from the group consisting of Co, Mn, Al and Mg. Further, x, y, and z are values satisfying all of 0.5 <x <1.2, 0.5 <y, 0 <z, and z = 1−y.

  The above-mentioned predetermined transition metal compound has a layered rock salt type structure, and can reversibly store and release metal ions. “Layered” means a sheet. The “rock salt type structure” is a sodium chloride type structure, which is a kind of crystal structure, in which face-centered cubic lattices formed by cations and anions are shifted from each other by の of a unit cell edge. Refers to the structure. The transition metal compound having the component ratio represented by the formula (1) has high ionic conductivity. Therefore, the discharge capacity of the all solid state secondary battery of the present invention can be improved. The transition metal compound is chemically stable.

Specific examples of the transition metal oxide represented by the formula (1) include lithium nickel composite oxide (LiNiO ₂ ), lithium nickel cobalt composite oxide (LiNiCoO ₂ ), and lithium nickel cobalt manganese composite oxide (LiNiCoMnO ₂ ). And those obtained by substituting a part of the metal of these oxides with magnesium or aluminum. Preferably, LiNiCoAlO ₂ or LiNiCoMnO ₂ is used. These may be used alone or in combination.

The positive electrode active material of the present invention may be a commercially available one, or may be manufactured by a known synthesis method. As an example, when synthesizing LiNiCoAlO ₂ , aluminum hydroxide, lithium hydroxide, lithium carbonate, and cobalt hydroxide can be mixed and fired at 700 to 800 ° C. for synthesis. Since lithium hydroxide has high volatility, it is added in excess when mixing the starting materials. After calcination, the obtained product is pulverized until it has a particle diameter suitable as a positive electrode active material. In the present invention, from the viewpoint of securing a large interface with the solid electrolyte, it is preferable that the particle size of the positive electrode active material be small. A specific range of the particle diameter is preferably from 0.1 to 20 μm, more preferably from 1 to 10 μm.

  As exemplified above, in the positive electrode active material of the present invention, as a result of excessive addition of lithium carbonate during its synthesis, unreacted lithium hydroxide tends to adhere to the product. It is presumed that the lithium hydroxide reacts with carbon dioxide and oxygen present in the exterior of the all-solid secondary battery during charge and discharge to generate a resistance component. The resistance component becomes an interface resistance between the positive electrode active material and the solid electrolyte, which causes a decrease in output of the all-solid secondary battery. Therefore, suppression of the generation amount of the resistance component is desired. The present invention reduces the amount of carbon dioxide and oxygen in the exterior body until a predetermined partial pressure is reached. Thereby, generation of the resistance component can be suppressed.

  In order to ensure a large area at the interface between the positive electrode active material and the solid electrolyte in the positive electrode, it is also preferable to include the solid electrolyte in the positive electrode. The solid electrolyte contained in the positive electrode may be the same as or different from the solid electrolyte constituting the solid electrolyte layer described later. Specific examples will be described in the description of the solid electrolyte layer.

  As the conductive agent contained in the positive electrode, a known material that contributes to improvement in conductivity can be used without limitation. Specific examples include Ketjen black, acetylene black, graphite, natural graphite, artificial graphite, and the like.

  As the binder contained in the positive electrode, a hydrocarbon polymer compound having a molecular weight of 100,000 to 100,000 is preferably used. Compounds having a molecular weight of less than 100 have poor binding properties and are not suitable as binders used in the present invention. A compound having a molecular weight of more than 100,000 increases the viscosity of the positive electrode mixture prepared when forming the positive electrode on the current collector, and thus reduces the coatability of the positive electrode slurry.

  Examples of the binder include styrene-based thermoplastic elastomers such as styrene-butadiene block polymer (SBS), styrene-ethylene-butadiene-styrene block polymer (SEBS), styrene- (styrene-butadiene) -styrene block polymer, and styrene-butadiene. Rubber (SBR), butadiene rubber (BR), natural rubber (NR), isoprene rubber (IR), ethylene-propylene-diene terpolymer (EPDM), and partially or completely hydrides thereof Can be Other examples include polystyrene, polyolefin, olefin-based thermoplastic elastomer, polycycloolefin, and silicone resin. A single binder may be used, or two or more binders may be used in combination.

  The method for forming the positive electrode of the present invention is not limited, but a preferred method is to apply a slurry-type positive electrode mixture onto a current collector and then dry it to remove the solvent. The current collector can be used without limitation as long as it is a conductive material. Examples include sheet or film copper, nickel, titanium, aluminum and the like. A non-polar solvent is selected as a solvent used for preparing the slurry-like positive electrode mixture. Specific examples include aromatic hydrocarbons such as toluene, xylene and ethylbenzene, and aliphatic hydrocarbons such as pentane, hexane and heptane. Thereby, the properties of the positive electrode mixture can be maintained in a slurry state.

  With respect to the content of the above components in 100 parts by mass of the positive electrode, the positive electrode active material is preferably 60 to 95 parts by mass, more preferably 70 to 90 parts by mass. The solid electrolyte is preferably from 5 to 40 parts by mass, more preferably from 10 to 30 parts by mass. By containing each component within the above preferred range, a positive electrode having good ion conductivity can be formed.

  The positive electrode mixture can be applied to the current collector using a die coater, a doctor blade, or the like. The positive electrode mixture applied on the current collector is heat-treated to remove the solvent. The heat treatment temperature is preferably 40 to 100 ° C., and the heat treatment time is preferably 10 to 30 minutes.

[Solid electrolyte layer]
The solid electrolyte layer of the present invention may contain a binder and a conductive agent in addition to the solid electrolyte. The same binder and conductive agent to be contained in the positive electrode can be used as the binder and the conductive agent.

  As the solid electrolyte used in the present invention, a conventionally known solid electrolyte such as a phosphoric acid-based solid electrolyte and a sulfide-based solid electrolyte can be used. Preferably, the first element contains sulfur (S), the second element contains lithium (Li), and the third element is selected from the group consisting of silicon (Si), boron (B), and phosphorus (P). A sulfide-based solid electrolyte containing at least one or more elements is used. In order to improve ionic conductivity, it is also preferable to include germanium (Ge) and the like in addition to the above elements.

Specific examples of the sulfide-based solid electrolyte include Li ₃ PS ₄ , Li ₄ P ₂ S ₇ , Li ₄ SiS ₄ , 50Li ₄ SiO ₄ , 50Li ₃ BO _{3 and the} like. The sulfide-based solid electrolyte may be any of amorphous, crystalline, glass, and glass-ceramic, but amorphous is preferably used because it tends to have high ionic conductivity. The ionic conductivity of the sulfide-based solid electrolyte used in the present invention is preferably 10 ^-2 to 10 ^-5 S / cm. When a solid electrolyte having an ionic conductivity lower than 10 ⁻⁵ S / cm is used, the charge / discharge capacity of the battery is significantly reduced.

  The method for forming the sulfide-based solid electrolyte layer is not limited, but includes a method in which a slurry-like solid electrolyte mixture is applied on a support made of polyethylene terephthalate and then dried to remove the solvent. The heat treatment temperature at the time of solvent removal is preferably 40 to 100 ° C., and the heat treatment time is preferably 10 to 30 minutes. The obtained solid electrolyte layer is separated from the support and incorporated into the secondary battery structure. As another method, there is a method in which the solid electrolyte powder and the binder powder are pressure-formed after stirring using a ball mill or the like.

  A binder and an inorganic compound are added to the above mixture in addition to the solid electrolyte. As the binder and the inorganic compound, those which can be added to the positive electrode mixture can be similarly used. The amount of the solid electrolyte added to 100 parts by mass of the solvent is preferably 90 to 99.9 parts by mass, and more preferably 95 to 99.5 parts by mass. The method for applying and drying the solid electrolyte mixture is the same as that for the positive electrode mixture.

As a method for producing a solid electrolyte, a mechanical milling method (MM method) can be applied. The MM method is a method in which the above-mentioned starting material and a ball mill or the like are placed in a reactor, vigorously stirred, and the starting material is atomized and mixed. In this case, it is preferable to mix Li ₂ S and P ₂ S ₅ as starting materials in a mixing ratio of 60:40 to 80:20. When the mixing amount of Li ₂ S is less than a predetermined range, an ion conductivity suitable for use in an all-solid secondary battery cannot be obtained.

  The solid electrolyte mixture applied to the support is subjected to a heat treatment to remove the solvent. By vacuum-drying the solid electrolyte mixed solution after the heat treatment, the solid electrolyte layer used in the present invention can be obtained. The vacuum drying is preferably performed at 30 to 100 ° C, more preferably at 40 to 80 ° C. The above-mentioned solid electrolyte layer is used after being separated from the support. The thickness is preferably 50 to 300 μm.

[Negative electrode]
The negative electrode constituting the present invention preferably contains at least a negative electrode active material and a binder, and also contains a solid electrolyte. By including the solid electrolyte, the area of the interface between the negative electrode active material and the solid electrolyte can be increased, and a large number of ion conduction paths can be secured. Examples of the negative electrode active material include artificial graphite, natural graphite, a mixture of artificial graphite and natural graphite, and natural graphite coated with artificial graphite. As the solid electrolyte, a known solid electrolyte can be used. The same or different solid electrolytes may be used as the solid electrolytes contained in the solid electrolyte layer.

  Although a method for forming the negative electrode is not limited, a method similar to the method for forming the positive electrode can be applied. That is, it can be formed by preparing a slurry mixture to which a negative electrode active material, a binder, a conductive agent, a solid electrolyte and the like are added, coating the negative electrode mixture on a current collector, and drying. With respect to the content of each component in 100 parts by mass of the negative electrode, the negative electrode active material is preferably 60 to 95 parts by mass, more preferably 75 to 90 parts by mass. The solid electrolyte is preferably 5 to 40 parts by mass, more preferably 10 to 25 parts by mass. By containing each component within the above preferred range, a negative electrode having good ion conductivity can be formed. The method for applying and drying the negative electrode mixture is the same as that for the positive electrode mixture.

[Method of manufacturing all solid state secondary battery]
In the method for manufacturing an all-solid secondary battery according to the present invention, first, a solid electrolyte layer is disposed between the above-described positive electrode and negative electrode, and this is molded under pressure to assemble the cell. The cell is installed in an exterior body. After the cell is installed, the partial pressure of carbon dioxide and oxygen is reduced from the exterior body, and the exterior body is sealed by heat compression or the like. As the outer package, a laminate pack of aluminum, stainless steel, or the like, or a cylindrical or square metal container is preferable.

[Step of reducing the partial pressure of carbon dioxide and oxygen]
In the present invention, the partial pressures of carbon dioxide and oxygen are reduced until the total partial pressure of carbon dioxide and oxygen in the exterior body after this step becomes 200 Pa or less. The total value of the above partial pressures is more preferably 20 Pa or less, and the smaller the better, the better. Thereby, the production of lithium carbonate due to the reaction between lithium hydroxide, carbon dioxide, and oxygen that occur in the outer package during charging and discharging of the all-solid secondary battery can be suppressed.

  In the present invention, a predetermined transition metal oxide is used as a positive electrode active material. This transition metal oxide may be used in a state where lithium hydroxide as its starting material is adhered. However, according to the present invention, since the total partial pressure of carbon dioxide and oxygen is reduced to the above-described predetermined value in the exterior body, even if a transition metal oxide to which lithium hydroxide is attached is used as the positive electrode active material, The amount of lithium carbonate generated can be reduced, and the interface resistance between the positive electrode active material and the solid electrolyte can be reduced.

  Preferred methods for reducing the partial pressure between carbon dioxide and oxygen include evacuating the exterior body or replacing carbon dioxide and oxygen with an inert gas. When evacuation is performed, a vacuum machine can be used. An inert gas may be introduced into the package after evacuation. In addition, if the cell is manufactured and the cell is placed in the outer package in an inert atmosphere, the evacuation process can be omitted, and the manufacturing cost can be reduced. As the inert gas, at least one gas selected from the group consisting of helium, nitrogen, neon, argon, krypton, and xenon is preferably used.

  FIG. 3 is a measurement result of an IR spectrum of lithium carbonate in a case after one cycle of an all-solid secondary battery in which a cell having the following cell configuration is sealed in a case made of an aluminum laminate. In FIG. 3, a solid line shows a case where the step of reducing the partial pressure of carbon dioxide and oxygen is performed by evacuation. The broken line shows the case where the step of reducing the partial pressure of carbon dioxide and oxygen is performed by evacuating and replacing with argon gas. The dashed line indicates the case where the step of reducing the partial pressure of carbon dioxide and oxygen was not performed. The step of reducing the partial pressure of carbon dioxide and oxygen was performed until the total partial pressure of carbon dioxide and oxygen reached 20 Pa.

[Cell configuration]
(Current collector) Al / (Positive electrode) LiNi _0.8 Co _0.15 Al _0.05 / (Solid electrolyte layer) Li ₂ SP ₂ S ₅ / (Negative electrode) Graphite / (Current collector) Cu

[Diffuse reflection method IR spectrum measurement method]
Disassemble the all-solid-state secondary battery in an argon box, fill the sample holder with the shaved cathode active material, and transfer it to Jasco FT / IR-6200 using a vacuum chamber so that it does not come into contact with the atmosphere. Diffuse reflection IR measurement was performed.

As shown in FIG. 3, when the step of reducing the partial pressure of carbon dioxide and oxygen is not performed, a peak is observed in the range of 1400 to 1600 cm ⁻¹ . From this measurement result, it can be read that lithium carbonate is remarkably present in the exterior body. On the other hand, in the case where the predetermined step of reducing the partial pressure of carbon dioxide and oxygen according to the present invention is performed, no peak is observed within the above range. That is, it can be seen that the amount of lithium carbonate present in the exterior body was extremely small, and the amount of lithium carbonate generated by the reaction between lithium hydroxide and carbon dioxide or the like adhering to the positive electrode active material was suppressed. That is, according to the present invention, by reducing the partial pressure of carbon dioxide and oxygen in the outer package, the lithium carbonate generation reaction can be suppressed, and the resistance at the interface between the positive electrode active material and the solid electrolyte can be reduced.

  The present invention will be further described with reference to examples. However, the present invention is not limited to the following examples.

[Example 1]
(Preparation of positive electrode structure)
Ternary powder as a positive electrode active material, Li ₂ SP ₂ S ₅ (80:20 mol%) amorphous powder as a sulfide-based solid electrolyte, and gas phase as a positive electrode conductive material (conductive auxiliary) The growth carbon fiber powder was weighed at a mass ratio of 60: 35: 5, and mixed using a rotation and revolution mixer.

  To this mixed powder, a dehydrated xylene solution in which SBR as a binder was dissolved was added so that SBR was 5.0% by mass with respect to the total mass of the mixed powder, to produce a primary mixed solution. Further, an appropriate amount of dehydrated xylene for adjusting the viscosity was added to the primary mixed solution to form a secondary mixed solution. Further, in order to improve the dispersibility of the mixed powder, a zirconia ball having a diameter of 5 mm is added to the secondary mixed liquid so that the space, the mixed powder, and the zirconia ball each occupy 1/3 of the total volume of the kneading vessel. I put it in. The generated tertiary mixed solution was charged into a rotation and revolution mixer, and stirred at 3000 rpm for 3 minutes to produce a positive electrode mixture.

  An aluminum foil current collector having a thickness of 15 μm was prepared as a positive electrode current collector, the positive electrode current collector was placed on a desktop screen printer, and a positive electrode mixture was applied on a sheet using a 150 μm metal mask. Thereafter, the sheet coated with the positive electrode mixture was dried on a hot plate at 60 ° C. for 30 minutes, and then vacuum-dried at 80 ° C. for 12 hours. Thus, a positive electrode was formed on the positive electrode current collector. The total thickness of the dried positive electrode current collector and the positive electrode was about 165 μm.

  A positive electrode structure was produced by rolling a sheet including the positive electrode current collector and the positive electrode using a roll press having a roll gap of 10 μm. The thickness of the positive electrode structure was around 120 μm.

[Preparation of negative electrode structure]
Graphite powder (which was vacuum-dried at 80 ° C. for 24 hours) as a negative electrode active material and PVdF as a binder were weighed at a mass ratio of 95.0: 5.0. Then, these materials and an appropriate amount of NMP were put into a rotation and revolution mixer, stirred at 3000 rpm for 3 minutes, and then subjected to defoaming treatment for 1 minute to produce a negative electrode coating liquid.

  A copper foil current collector having a thickness of 16 μm was prepared as a negative electrode current collector, and a negative electrode coating solution was applied on the copper foil current collector using a blade. The thickness (gap) of the negative electrode coating solution on the copper foil current collecting member was about 150 μm. The sheet coated with the negative electrode coating liquid was stored in a dryer heated to 80 ° C., and dried for 15 minutes. Further, the dried sheet was vacuum dried at 80 ° C. for 24 hours. Thus, a negative electrode structure was produced. The thickness of the positive electrode structure was around 140 μm.

[Preparation of electrolyte layer]
Dehydrated xylene solution in which SBR is dissolved in Li ₂ SP ₂ S ₅ (80:20 mol%) amorphous powder as a sulfide-based solid electrolyte so that SBR becomes 2.0 mass% with respect to the total mass of the mixed powder. To form a primary mixture. Further, an appropriate amount of dehydrated xylene for adjusting the viscosity was added to the primary mixed solution to form a secondary mixed solution. Further, in order to improve the dispersibility of the mixed powder, a zirconia ball having a diameter of 5 mm is added to the tertiary mixed liquid such that the space, the mixed powder, and the zirconia ball each occupy 1/3 of the total volume of the kneading vessel. I put it in. The tertiary mixed liquid thus generated was put into a rotation and revolution mixer, and stirred at 3000 rpm for 3 minutes to generate an electrolyte layer coating liquid.

  The negative electrode structure was placed on a desktop screen printer, and a coating liquid for an electrolyte layer was applied on the negative electrode structure using a 500 μm metal mask. Thereafter, the sheet coated with the electrolyte layer coating solution was dried on a hot plate at 40 ° C. for 10 minutes, and then vacuum dried at 40 ° C. for 12 hours. Thus, an electrolyte layer was formed on the negative electrode structure. The total thickness of the dried electrolyte layer was about 300 μm.

[Assembly of all solid state secondary battery]
The negative electrode structure, the solid electrolyte layer sheet, and the positive electrode structure are each punched out with a Thomson blade, and the electrolyte layer of the sheet and the positive electrode of the positive electrode structure are bonded by a dry lamination method using a roll press having a roll gap of 150 μm. Then, a single cell of a solid battery was assembled.

[Enclosure of all solid state secondary batteries]
The assembled single cell was placed in an aluminum laminated film to which terminals were attached, evacuated to 100 Pa with a vacuum machine, and heat-sealed to pack. The total value of the partial pressures of oxygen and carbon dioxide in the outer package after evacuation was 20 Pa.

[Measurement of pressure inside solid state battery]
The solid battery was immersed in oil, the aluminum laminate film was broken, and the amount of gas coming out of the battery was examined. From the comparison between the internal volume of the battery and the amount of generated gas, the pressure inside the battery was determined.

[Method for measuring atmosphere inside solid state battery]
The gas in the aluminum laminate film was sampled using a syringe, and the components of the gas were measured using gas chromatography to determine the proportions of oxygen and carbon dioxide in the battery.

[Partial pressure inside solid state battery]
The partial pressures of oxygen and carbon dioxide were calculated from the pressure inside the battery and the ratios of oxygen and carbon dioxide in the battery determined above.

[Example 2-7, Comparative example 1-11]
A positive electrode structure, a negative electrode structure, and a solid electrolyte layer were prepared in the same manner as in Example 1, except that the positive electrode active material was changed to a material described in Table 1 or Table 2, and was included in an aluminum laminate film package. Was. Thereafter, a step of reducing the partial pressure of carbon dioxide and oxygen was performed by the method described in Table 1, heat sealing was performed, and the resultant was packed to obtain Example 2-7 and Comparative Example 1-11.

  With respect to Example 1-7 and Comparative Example 1-11, the atmosphere, the single cell capacity, and the discharge capacity retention rate of the package were measured. Tables 1 and 2 show the measurement results.

[Evaluation method for single cell capacity]
The capacity (Ah) of the single cell was measured by a charge / discharge evaluation device TOSCAT-3100 manufactured by Toyo System. In Tables 1 and 2, the capacitance values of Example 2-7 and Comparative Example 1-11 were indexed by setting the capacitance value of Example 1 to 100.

[Calculation method of discharge capacity retention rate]
A constant current charge / discharge cycle test of 0.05 C at room temperature was performed. The discharge capacity at the first cycle was compared. The rate of decrease in the discharge capacity at the 50th cycle with respect to the discharge capacity at the first cycle was calculated as the maintenance rate of the discharge capacity.

100 All-solid secondary battery 201 Positive electrode 202 Current collector 301 Negative electrode 302 Current collector 400 Solid electrolyte layer 500 Outer body

Claims (3)

A package containing a positive electrode containing a transition metal oxide represented by the following formula (1) as a positive electrode active material, a negative electrode, and a solid electrolyte layer existing between the positive electrode and the negative electrode; The sum of the partial pressures of carbon dioxide and oxygen is 200 Pa or less,
The outer body contains at least one or more inert gases selected from the group consisting of helium, nitrogen, neon, argon, krypton, and xenon,
An all-solid secondary battery in which the positive electrode includes a positive electrode active material having lithium hydroxide attached to its surface .
(In the above formula (1), M is one or more elements selected from the group consisting of Co, Mn, Al, and Mg. X, y, and z are 0.5 <x <1.2 and 0.5 <y; It is a value that satisfies all of 0 <z and z = 1−y.) Solid electrolyte forming the solid electrolyte layer, first element, which contains the second element and third element, a sulfur (S) as the first element, lithium (Li as the secondary element ) containing silicon (Si) as the third element, boron (B), all-solid secondary of claim 1 containing at least one or more elements selected from the group consisting of phosphorus (P) battery. A package comprising a positive electrode containing a transition metal oxide represented by the formula (1) as a positive electrode active material having lithium hydroxide attached to its surface , a negative electrode, and a solid electrolyte layer disposed between the positive electrode and the negative electrode The step of reducing the total partial pressure of carbon dioxide and oxygen present in the outer casing of the all solid state secondary battery to be set to 200 Pa or less,
The step of reducing the total partial pressure of carbon dioxide and oxygen to 200 Pa or less, the carbon dioxide and the oxygen in the outer casing, helium, nitrogen, neon, argon, krypton, at least selected from the group consisting of xenon Replacing with one or more inert gases.
A method for manufacturing an all-solid secondary battery.
(In the above formula (1), M is one or more elements selected from the group consisting of Co, Mn, Al, and Mg. X, y, and z are 0.5 <x <1.2 and 0.5 <y; It is a value that satisfies all of 0 <z and z = 1−y.)