All-solid-state battery and evaluation method thereof

Abstract

To provide an all-solid-state battery in which initial failure can be detected while the occurrence of a short circuit is suppressed, a manufacturing method of the all-solid-state battery, and an evaluation method of the all-solid-state battery.SOLUTION: An all-solid-state battery includes a solid electrolyte layer, a first electrode layer which is provided on a first main surface of the solid electrolyte layer and contains an electrode active material, and a second electrode layer which is provided on a second main surface of the solid electrolyte layer and contains an electrode active material. When the all-solid-state battery is heated at a temperature increase rate of 20°C / min, per unit volume (cm3) of the all-solid-state battery, 30 mg or more and 53 mg or less of CO2 is generated externally from 550°C to 700°C, and 90 mg or more and 155 mg or less of CO2 is generated externally from 550°C to 750°C.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an all-solid-state battery and an evaluation method thereof. [Background technology]

[0002] All-solid-state batteries using oxide-based solid electrolytes are expected to be a technology that can provide safe secondary batteries that do not suffer from concerns about fires or the generation of toxic gases, which are common with organic electrolytes, sulfide-based solid electrolytes, etc. Because such all-solid-state batteries are small components, a technology is required to efficiently detect early defects. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 026009 Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, in order to detect initial defects such as minute cracks, structural defects, and internal cracks that cannot be detected by appearance, it is conceivable to detect gas generated from an all-solid-state battery when heated. For example, Patent Document 1 discloses a technique for impregnating an all-solid-state battery with water, and this technique could be used to detect moisture leaking as the temperature rises. However, if an all-solid-state battery contains water, there is a risk that certain components in the all-solid-state battery will leach out. Therefore, it is conceivable to use other gases. However, if a large amount of gas is contained in an all-solid-state battery, there is a risk of a short circuit occurring.

[0005] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide an all-solid-state battery and an evaluation method thereof that can detect initial defects while suppressing the occurrence of short circuits. [Means for solving the problem]

[0006] The all-solid-state battery according to the present invention is an all-solid-state battery comprising a solid electrolyte layer, a first electrode layer provided on a first main surface of the solid electrolyte layer and containing an electrode active material, and a second electrode layer provided on a second main surface of the solid electrolyte layer and containing an electrode active material, wherein when heated at a temperature rise rate of 20°C / min, the all-solid-state battery has a unit volume (cm 3 ) between 550°C and 700°C, and between 90mg and 155mg of CO2 are generated externally.

[0007] In the all-solid-state battery, the solid electrolyte layer may have voids therein that contain CO2.

[0008] In the all-solid-state battery, the solid electrolyte layer may have a thickness of 5 μm or more and 30 μm or less.

[0009] The method for evaluating an all-solid-state battery according to the present invention is characterized in that, when a charge-discharge test is performed on any of the all-solid-state batteries described above, CO is detected from the all-solid-state battery to the outside, thereby evaluating the all-solid-state battery. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an all-solid-state battery capable of detecting initial defects while suppressing the occurrence of short circuits, a method for manufacturing an all-solid-state battery, and a method for evaluating an all-solid-state battery. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic cross-sectional view showing the basic structure of an all-solid-state battery. [Figure 2] FIG. 1 is a schematic cross-sectional view of an all-solid-state battery according to an embodiment. [Figure 3] FIG. 1 is a schematic cross-sectional view of another all-solid-state battery. [Figure 4] FIG. 10 is a diagram illustrating the amount of CO2 externally generated from an all-solid-state battery when the temperature rise rate is set to 20° C. / min. [Figure 5] FIG. 2 is a diagram illustrating an SEM image of a cross section of a solid electrolyte layer according to an embodiment. [Figure 6] FIG. 1 is a diagram illustrating a flow of a method for manufacturing an all-solid-state battery. [Figure 7] 1(a) and 1(b) are diagrams illustrating the lamination process. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments will be described with reference to the drawings.

[0013] (Embodiment) Fig. 1 is a schematic cross-sectional view showing the basic structure of an all-solid-state battery 100. As illustrated in Fig. 1, the all-solid-state battery 100 has a structure in which a solid electrolyte layer 30 is sandwiched between a first internal electrode 10 (first electrode layer) and a second internal electrode 20 (second electrode layer). The first internal electrode 10 is formed on a first main surface of the solid electrolyte layer 30. The second internal electrode 20 is formed on a second main surface of the solid electrolyte layer 30.

[0014] When the all-solid-state battery 100 is used as a secondary battery, one of the first internal electrode 10 and the second internal electrode 20 is used as a positive electrode, and the other is used as a negative electrode. In this embodiment, as an example, the first internal electrode 10 is used as a positive electrode layer, and the second internal electrode 20 is used as a negative electrode layer.

[0015] The solid electrolyte layer 30 has a NASICON-type crystal structure and is mainly composed of an oxide-based solid electrolyte having ion conductivity. The solid electrolyte of the solid electrolyte layer 30 is, for example, an oxide-based solid electrolyte having lithium ion conductivity. The solid electrolyte is, for example, a phosphate-based solid electrolyte. A phosphate-based solid electrolyte having a NASICON-type crystal structure has high conductivity and is stable in the air. The phosphate-based solid electrolyte is, for example, a phosphate containing lithium. The phosphate is not particularly limited, but examples include composite lithium phosphate salts with Ti (e.g., LiTi2(PO4)3). Alternatively, Ti can be partially or completely substituted with a tetravalent transition metal such as Ge, Sn, Hf, or Zr. Furthermore, to increase the Li content, it may be partially substituted with a trivalent transition metal such as Al, Ga, In, Y, or La. More specifically, for example, Li 1+x Al x Ge 2-x (PO4)3 and Li 1+x Al x Zr 2-x (PO4)3, Li 1+x Al x Ti 2-x (PO4)3, etc. For example, a Li-Al-Ge-PO4-based material to which the same transition metal as that contained in the phosphate having an olivine crystal structure contained in the first internal electrode 10 and the second internal electrode 20 has been added in advance is preferred. For example, when the first internal electrode 10 and the second internal electrode 20 contain a phosphate containing Co and Li, it is preferred that the solid electrolyte layer 30 contain a Li-Al-Ge-PO4-based material to which Co has been added in advance. In this case, it is possible to obtain an effect of suppressing the elution of the transition metal contained in the electrode active material into the electrolyte. When the first internal electrode 10 and the second internal electrode 20 contain a phosphate containing Li and a transition element other than Co, it is preferred that the solid electrolyte layer 30 contain a Li-Al-Ge-PO4-based material to which the transition metal has been added in advance.

[0016] The first internal electrode 10 used as a positive electrode contains a substance having an olivine crystal structure as an electrode active material. It is preferable that the second internal electrode 20 also contains the electrode active material. An example of such an electrode active material is a phosphate containing a transition metal and lithium. The olivine crystal structure is a crystal possessed by natural olivine, and can be identified by X-ray diffraction.

[0017] A typical example of an electrode active material with an olivine crystal structure is LiCoPO4, which contains Co. Phosphates in which the transition metal Co is substituted in this chemical formula can also be used. The ratio of Li and PO4 can vary depending on the valence. It is preferable to use Co, Mn, Fe, Ni, etc. as the transition metal.

[0018] The electrode active material having an olivine-type crystal structure acts as a positive electrode active material in the first internal electrode 10 that acts as a positive electrode. For example, when only the first internal electrode 10 contains an electrode active material having an olivine-type crystal structure, the electrode active material acts as a positive electrode active material. When the second internal electrode 20 also contains an electrode active material having an olivine-type crystal structure, the second internal electrode 20 that acts as a negative electrode exhibits the effects of increasing the discharge capacity and increasing the operating potential with discharge, which are presumed to be based on the formation of a partial solid solution state with the negative electrode active material, although the mechanism of action is not fully understood.

[0019] When both the first internal electrode 10 and the second internal electrode 20 contain an electrode active material having an olivine crystal structure, the respective electrode active materials preferably contain transition metals that may be the same or different from each other. The phrase "may be the same or different from each other" means that the electrode active materials contained in the first internal electrode 10 and the second internal electrode 20 may contain the same type of transition metal or different types of transition metals. The first internal electrode 10 and the second internal electrode 20 may contain only one type of transition metal or two or more types of transition metals. Preferably, the first internal electrode 10 and the second internal electrode 20 contain the same type of transition metal. More preferably, the electrode active materials contained in both electrodes have the same chemical composition. The first internal electrode 10 and the second internal electrode 20 contain the same type of transition metal or electrode active material with the same composition, which increases the similarity of the compositions of the two internal electrode layers, has the effect of being able to withstand actual use without malfunctioning depending on the application, even if the terminals of the all-solid-state battery 100 are attached in reverse.

[0020] The second internal electrode 20 contains a negative electrode active material. By including a negative electrode active material in only one electrode, it becomes clear that the one electrode functions as a negative electrode and the other electrode functions as a positive electrode. It is also possible to include a material known as a negative electrode active material in both electrodes. Regarding the negative electrode active material of the electrode, reference can be made to conventional secondary battery technology, and examples include compounds such as titanium oxide, lithium titanium composite oxide, lithium titanium composite phosphate, carbon, and lithium vanadium phosphate.

[0021] In the production of the first internal electrode 10 and the second internal electrode 20, in addition to these electrode active materials, a solid electrolyte having ion conductivity, a conductive material (conductive additive), etc. are added. For these components, an internal electrode paste can be obtained by uniformly dispersing a binder and a plasticizer in water or an organic solvent. A carbon material or the like may be included as the conductive additive. A metal may be included as the conductive additive. Examples of the metal for the conductive additive include Pd, Ni, Cu, Fe, and alloys containing these. The solid electrolyte included in the first internal electrode 10 and the second internal electrode 20 can be, for example, the same as the main solid electrolyte of the solid electrolyte layer 30.

[0022] The thickness of the solid electrolyte layer 30 is, for example, 5 μm to 30 μm, 7 μm to 25 μm, or 10 μm to 20 μm. The thickness of the first internal electrode 10 and the second internal electrode 20 is, for example, 5 μm to 50 μm, 7 μm to 45 μm, or 10 μm to 40 μm. The thickness of each layer can be measured, for example, as the average value of thicknesses at 10 different points on one layer.

[0023] 2 is a schematic cross-sectional view of a stacked-type all-solid-state battery 100a in which a plurality of battery units are stacked. The all-solid-state battery 100a includes a stacked chip 60 having a substantially rectangular parallelepiped shape. In the stacked chip 60, a first external electrode 40a and a second external electrode 40b are provided so as to contact two side surfaces, which are two of the four surfaces other than the top and bottom surfaces at the ends in the stacking direction. The two side surfaces may be two adjacent side surfaces or two side surfaces facing each other. In this embodiment, the first external electrode 40a and the second external electrode 40b are provided so as to contact two side surfaces facing each other (hereinafter referred to as two end surfaces).

[0024] In the following description, components having the same composition range, thickness range, and particle size distribution range as those of the all-solid-state battery 100 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0025] In the all-solid-state battery 100a, a plurality of first internal electrodes 10 and a plurality of second internal electrodes 20 are alternately stacked with solid electrolyte layers 30 interposed therebetween. The edges of the plurality of first internal electrodes 10 are exposed at the first end face of the laminated chip 60 but are not exposed at the second end face. The edges of the plurality of second internal electrodes 20 are exposed at the second end face of the laminated chip 60 but are not exposed at the first end face. As a result, the first internal electrodes 10 and the second internal electrodes 20 are alternately electrically connected to the first external electrode 40a and the second external electrode 40b. The solid electrolyte layer 30 extends from the first external electrode 40a to the second external electrode 40b. In this way, the all-solid-state battery 100a has a structure in which a plurality of battery units are stacked.

[0026] A cover layer 50 is laminated on the upper surface of the laminated structure of the first internal electrode 10, the solid electrolyte layer 30, and the second internal electrode 20 (in the example of FIG. 2, on the upper surface of the first internal electrode 10, which is the uppermost layer). In addition, a cover layer 50 is laminated on the lower surface of the laminated structure (in the example of FIG. 2, on the lower surface of the first internal electrode 10, which is the lowermost layer). The cover layer 50 is mainly composed of an inorganic material containing, for example, Al, Si, Zr, Ti, etc. (for example, Al2O3, SiO2, ZrO2, TiO2, etc.). The cover layer 50 may contain the main component of the solid electrolyte layer 30 as a main component.

[0027] The first internal electrode 10 and the second internal electrode 20 may each include a current collector layer. For example, as illustrated in FIG. 3, a first current collector layer 11 may be provided within the first internal electrode 10. Furthermore, a second current collector layer 21 may be provided within the second internal electrode 20. The first current collector layer 11 and the second current collector layer 21 are mainly composed of a conductive material. For example, metal, carbon, or the like can be used as the conductive material for the first current collector layer 11 and the second current collector layer 21. Connecting the first current collector layer 11 to the first external electrode 40a and connecting the second current collector layer 21 to the second external electrode 40b improves current collection efficiency.

[0028] Because all-solid-state batteries are generally small components, technology is required to efficiently detect initial defects. Examples of initial defects include minute cracks, structural defects, and internal cracks that cannot be detected by appearance. If an all-solid-state battery experiencing an initial defect contains gas components inside, when a charge-discharge test is performed, the gas components will be emitted (leaked) from the all-solid-state battery to the outside. Therefore, by determining whether or not the gas components are detected when conducting a charge-discharge test of an all-solid-state battery, it becomes possible to determine whether or not an all-solid-state battery has an initial defect.

[0029] Therefore, for example, it is conceivable to incorporate a predetermined amount of moisture into the all-solid-state battery and detect the moisture that is generated from the all-solid-state battery to the outside when heated. However, if moisture is contained in the all-solid-state battery, there is a risk that specific components in the all-solid-state battery will leach into the moisture. Therefore, in this embodiment, attention is focused on CO2 (carbon dioxide).

[0030] In this embodiment, CO2 gas is contained in the all-solid-state battery 100a by containing CO2 gas in voids inside the solid electrolyte layer 30. With this structure, if the all-solid-state battery 100a has an initial defect such as a minute crack, a structural defect, or an internal crack that cannot be detected by appearance, when a charge-discharge test is performed on the all-solid-state battery 100a, CO2 is generated from the all-solid-state battery 100a to the outside due to a rise in temperature. Therefore, by performing a charge-discharge test and determining whether or not CO2 is detected, it becomes possible to determine whether or not an initial defect has occurred in the all-solid-state battery 100a.

[0031] However, if the amount of CO2 contained in the all-solid-state battery 100a is small, there is a risk that CO2 generation will not be detected during a charge-discharge test even if an initial defect occurs. Therefore, it is preferable to set a lower limit for the amount of CO2 to be contained in the all-solid-state battery 100a. Since it is difficult to measure the amount of CO2 contained in the all-solid-state battery 100a at room temperature, the amount of CO2 generated outside from the all-solid-state battery 100a when the all-solid-state battery 100a is heated is specified.

[0032] 4 is a diagram illustrating the amount of CO2 generated externally from the all-solid-state battery 100a when the temperature rise rate is 20°C / min. As illustrated in FIG. 4, when the all-solid-state battery 100a is heated, CO2 is generated when the temperature exceeds about 550°C, the rate of increase slows when the temperature exceeds about 650°C, and the amount of CO2 generated tends to increase sharply from above 700°C to about 750°C. The increase in the amount of CO2 generated from above 700°C to about 750°C is thought to be due to the release of CO2 as the solid electrolyte crystallizes.

[0033] Therefore, in this embodiment, when the temperature rise rate is set to 20°C / min, the amount of CO2 contained in the all-solid-state battery 100a is specified in two stages: the amount of CO2 generated from 550°C to 700°C, and the amount of CO2 generated from 550°C to 750°C. Specifically, when the all-solid-state battery 100a is heated, the amount of CO2 generated from 550°C to 700°C is 30 mg / cm. 3 More than 90 mg / cm2 of CO2 is generated between 550 and 750°C. 3 The all-solid-state battery 100a contains CO2 so that the above CO2 is generated. From the viewpoint of more reliably detecting CO2 generation during charge / discharge tests, the CO2 content is set to 60 mg / cm2 from 550°C to 700°C. 3 More than 160 mg / cm2 of CO2 is generated between 550 and 750°C. 3 It is preferable that CO2 is generated at a rate of 80 mg / cm between 550 and 700 °C. 3 More than 200 mg / cm2 of CO2 is generated between 550 and 750°C. 3 It is more preferable that the amount of CO2 generated is more than this.

[0034] The above CO2 emissions are calculated in mg / cm 3 " is the unit volume (cm ) of the all-solid-state battery 100a 3 ) means the amount of CO2 generated (mg) per unit of space.

[0035] On the other hand, if the amount of CO2 contained in the all-solid-state battery 100a is large, the insulation resistance of the solid electrolyte decreases, which may cause a short circuit. Therefore, it is preferable to set an upper limit on the amount of CO2 contained in the all-solid-state battery 100a. Specifically, when the all-solid-state battery 100a is heated, the CO2 content is 53 mg / cm3 from 550°C to 700°C. 3 The following CO2 is generated: 155 mg / cm between 550 and 750 °C. 3 The all-solid-state battery 100a contains CO2 so that the following CO2 is generated: 40 mg / cm2 from 550°C to 700°C from the viewpoint of further suppressing the occurrence of short circuits. 3 The following CO2 is generated: 80 mg / cm between 550 and 750°C. 3 It is preferable that CO2 be generated at a rate of 20 mg / cm between 550 and 700 °C. 3 The following CO2 is generated: 50 mg / cm between 550 and 750 °C. 3 It is more preferable that the following CO2 is generated:

[0036] For example, a plurality of voids are formed in the solid electrolyte layer 30, and CO2 is contained in the voids. Fig. 5 is a diagram illustrating an SEM image of a cross section of the solid electrolyte layer 30. The cross section is, for example, a cross section along the stacking direction of the first internal electrode 10, the solid electrolyte layer 30, and the second internal electrode 20. As illustrated in Fig. 5, a plurality of voids 31 are formed in the solid electrolyte layer 30. CO2 is contained in each void 31.

[0037] Next, a description will be given of a method for manufacturing the all-solid-state battery 100a illustrated in Fig. 2. Fig. 6 is a diagram illustrating a flow of the method for manufacturing the all-solid-state battery 100a.

[0038] (Process for producing raw material powder for solid electrolyte layer) First, raw material powder for the solid electrolyte layer that constitutes the solid electrolyte layer 30 described above is prepared. For example, raw materials, additives, etc. are mixed and a solid-phase synthesis method or the like is used to prepare a solid electrolyte material for an oxide-based solid electrolyte. The obtained solid electrolyte material can be pulverized in the presence of an organic solvent to adjust the average particle size to a desired value. For example, the desired average particle size is adjusted using a planetary ball mill with 5 mm diameter ZrO2 balls. By pulverizing in the presence of an organic solvent, organic groups with oxygen (O), such as ethoxy groups and propyl groups, chemically bond to dangling bonds on the surface of the raw material powder. The organic group with oxygen (O) is, for example, an alkoxy group expressed by an R-O bond (R is an alkyl group, etc.).

[0039] (Cover layer raw material powder production process) First, a ceramic raw material powder for the cover layer 50 is prepared. For example, raw materials, additives, etc. are mixed and solid-phase synthesis is used to prepare the raw material powder for the cover layer. The obtained raw material powder can be adjusted to a desired average particle size by dry milling. For example, the desired average particle size is adjusted using a planetary ball mill with 5 mm diameter ZrO2 balls. If the solid electrolyte layer 30 and the cover layer 50 have the same composition, the raw material powder for the solid electrolyte layer can be used instead.

[0040] (Internal electrode paste manufacturing process) Next, an internal electrode paste for producing the first internal electrode 10 and the second internal electrode 20 is prepared. For example, the internal electrode paste can be obtained by uniformly dispersing a conductive additive, an electrode active material, a solid electrolyte material, a sintering additive, a binder, a plasticizer, etc. in water or an organic solvent. The solid electrolyte material may be the above-mentioned solid electrolyte paste. A carbon material or the like may be used as the conductive additive. A metal may be used as the conductive additive. Examples of the metal conductive additive include Pd, Ni, Cu, Fe, and alloys containing these. Pd, Ni, Cu, Fe, alloys containing these, and various carbon materials may also be used. If the first internal electrode 10 and the second internal electrode 20 have different compositions, a paste for each internal electrode may be prepared separately.

[0041] The sintering aid of the internal electrode paste contains one or more glass components such as Li-BO based compounds, Li-Si-O based compounds, Li-CO based compounds, Li-SO based compounds, and Li-PO based compounds.

[0042] (External electrode paste manufacturing process) Next, an external electrode paste for producing the first external electrode 40a and the second external electrode 40b is prepared. For example, the external electrode paste can be obtained by uniformly dispersing a conductive material, glass frit, a binder, a plasticizer, etc. in water or an organic solvent.

[0043] (Solid electrolyte green sheet manufacturing process) The raw material powder for the solid electrolyte layer is uniformly dispersed in an aqueous or organic solvent along with a binder, dispersant, plasticizer, etc., and then wet-pulverized to obtain a solid electrolyte slurry with a desired average particle size. This process can be performed using a bead mill, wet jet mill, various kneaders, high-pressure homogenizers, etc., with the bead mill being preferred because it allows for simultaneous adjustment of particle size distribution and dispersion. A binder is added to the resulting solid electrolyte slurry to obtain a solid electrolyte paste. The resulting solid electrolyte paste can be coated to produce a solid electrolyte green sheet 51. The coating method is not particularly limited, and can include slot die coating, reverse coating, gravure coating, bar coating, doctor blade coating, etc. The particle size distribution after wet-pulverization can be measured, for example, using a laser diffraction measurement device using laser diffraction scattering.

[0044] (Lamination process) As shown in FIG. 7( a), an internal electrode paste 52 is printed on one side of a solid electrolyte green sheet 51. The thickness of the internal electrode paste 52 is equal to or greater than the thickness of the solid electrolyte green sheet 51. A reverse pattern 53 is printed on the area of ​​the solid electrolyte green sheet 51 where the internal electrode paste 52 is not printed. The reverse pattern 53 may be the same as the solid electrolyte green sheet 51. Multiple printed solid electrolyte green sheets 51 are stacked with an alternating offset. As shown in FIG. 7( b), a laminate is obtained by pressing cover sheets 54 from above and below in the stacking direction. In this case, a laminate having a substantially rectangular parallelepiped shape is obtained so that the internal electrode paste 52 is exposed alternately on two end faces of the laminate. The cover sheet 54 can be formed by coating raw material powder for the cover layer using a method similar to the solid electrolyte green sheet preparation process. The cover sheet 54 is formed thicker than the solid electrolyte green sheet 51. The thickness may be increased during coating, or by stacking multiple coated sheets.

[0045] Next, external electrode paste 55 is applied to each of the two end faces by dipping or the like and then dried, thereby obtaining a molded body for forming the all-solid-state battery 100a.

[0046] (Firing process) Next, the obtained laminate is fired. The firing conditions are not particularly limited, and may be in an oxidizing atmosphere or a non-oxidizing atmosphere, with the maximum temperature preferably being 400°C to 1000°C, more preferably 500°C to 900°C. A step of maintaining the temperature in an oxidizing atmosphere at a temperature lower than the maximum temperature may be provided in order to thoroughly remove the binder before the maximum temperature is reached. In order to reduce process costs, it is desirable to fire at as low a temperature as possible. After firing, a re-oxidation treatment may be performed. Through the above steps, an all-solid-state battery 100a is produced.

[0047] In addition, by sequentially stacking the internal electrode paste, the current collector paste containing a conductive material, and the internal electrode paste, a current collector layer can be formed within the first internal electrode 10 and the second internal electrode 20.

[0048] In the manufacturing method according to this embodiment, organic groups interposed by oxygen, such as ethoxy groups and propyl groups, are chemically bonded to the surface of the raw material powder for the solid electrolyte layer. Because the organic groups interposed by oxygen are stably bonded, they tend to remain even when the raw material powder begins to sinter and densify. The organic groups interposed by oxygen are desorbed and gasified in the firing process after the ambient temperature exceeds the sintering initiation temperature. In this case, since the solid electrolyte is densified around the organic groups interposed by oxygen, the gas is not released to the outside but becomes spherical. The spherical gas forms voids 31. The gasified organic groups interposed by oxygen are oxidized to CO2.

[0049] For example, the amount of CO2 contained in the solid electrolyte layer 30 can be adjusted by adjusting the firing conditions such as the average particle size of the raw material powder for the solid electrolyte layer, the firing temperature in the firing step, and the firing time in the firing step.

[0050] The method for incorporating CO2 into the solid electrolyte layer 30 is not limited to the above. For example, CO2 can be incorporated into the solid electrolyte layer 30 by heating the all-solid-state battery 100a in an atmosphere containing a large amount of CO2 gas. As an example, CO2 can be incorporated into the solid electrolyte layer 30 by heating it to about 700°C in an atmosphere of 90% N2 gas and 10% CO2 gas. Thereafter, CO2 is generated from the solid electrolyte layer 30 by heating it in a reduced pressure atmosphere, and the amount of CO2 in the solid electrolyte layer 30 can be adjusted. [Example]

[0051] An all-solid-state battery with 170 solid electrolyte layers was fabricated, with the structure shown in Figure 2. The dimensions of the all-solid-state battery were 4.5 mm x 3.2 mm x 3.2 mm.

[0052] Example 1 In Example 1, each sample was heated to 700°C in an atmosphere of 90% by volume of N2 gas and 10% by volume of CO2 gas to allow CO2 gas to be contained in the solid electrolyte layer. 3 The amount of CO2 gas in the solid electrolyte layer was adjusted by heating it to 700°C in an electric furnace controlled at Pa.

[0053] Example 2 In Example 2, each sample was heated to 700°C in an atmosphere of 90% by volume of N2 gas and 10% by volume of CO2 gas to allow CO2 gas to be contained in the solid electrolyte layer. 4 The amount of CO2 gas in the solid electrolyte layer was adjusted by heating up to 700°C in an electric furnace controlled at Pa. By increasing the pressure in the electric furnace compared to Example 1, the amount of CO2 gas remaining in the solid electrolyte layer was increased.

[0054] Example 3 In Example 3, each sample was heated to 700°C in an atmosphere of 90% by volume of N2 gas and 10% by volume of CO2 gas to allow CO2 gas to be contained in the solid electrolyte layer.4 The amount of CO2 gas in the solid electrolyte layer was adjusted by heating to 600°C in an electric furnace controlled at Pa. By lowering the temperature in the electric furnace compared to Example 2, the amount of CO2 gas remaining in the solid electrolyte layer was increased.

[0055] (Comparative Example 1) In Comparative Example 1, each sample was heated to 700°C in an atmosphere of 90% by volume of N2 gas and 10% by volume of CO2 gas to allow CO2 gas to be contained in the solid electrolyte layer. 2 The amount of CO2 gas in the solid electrolyte layer was adjusted by heating up to 700°C in an electric furnace controlled at Pa. By lowering the pressure in the electric furnace compared to Example 1, the amount of CO2 gas remaining in the solid electrolyte layer was reduced.

[0056] (Comparative Example 2) In Comparative Example 2, each sample was heated to 700°C in an atmosphere of 90% by volume of N2 gas and 10% by volume of CO2 gas to incorporate CO2 gas into the solid electrolyte layer. The sample was then heated to 600°C in an air atmosphere to adjust the amount of CO2 gas in the solid electrolyte layer. By heating under a higher pressure than in Example 3, the amount of CO2 gas remaining in the solid electrolyte layer was increased.

[0057] (Comparative Example 3) In Comparative Example 3, each sample was heated to 700°C in an atmosphere of 90% by volume of N gas and 10% by volume of CO gas, thereby containing CO gas in the solid electrolyte layer. By not adjusting the amount of CO gas in the solid electrolyte layer, the amount of CO gas remaining in the solid electrolyte layer was greater than in Comparative Example 2.

[0058] For each of Examples 1 to 3 and Comparative Examples 1 to 3, heating was performed at a temperature increase rate of 20°C / min, and the amount of CO2 (mg / cm) generated from 550°C to 700°C was measured. 3 ) and the amount of CO2 generated from 550 to 750°C (mg / cm 3 In Example 1, the amount of CO2 generated from 550°C to 700°C was 30 mg / cm 3The amount of CO2 generated between 550 and 750°C was 90 mg / cm 3 In Example 2, the amount of CO2 generated from 550°C to 700°C was 45 mg / cm 3 The amount of CO2 generated from 550 to 750°C was 125 mg / cm 3 In Example 3, the amount of CO2 generated from 550°C to 700°C was 53 mg / cm 3 The amount of CO2 generated from 550 to 750°C was 155 mg / cm 3 In Comparative Example 1, the amount of CO2 generated from 550°C to 700°C was 15 mg / cm 3 The amount of CO2 generated between 550 and 750°C was 45 mg / cm 3 In Comparative Example 2, the amount of CO2 generated from 550°C to 700°C was 60 mg / cm 3 The amount of CO2 generated from 550 to 750°C was 185 mg / cm 3 In Comparative Example 3, the amount of CO2 generated from 550°C to 700°C was 75 mg / cm 3 The amount of CO2 generated from 550 to 750°C was 215 mg / cm 3 The amount of CO2 was measured using gas chromatography.

[0059] One hundred samples of each of Examples 1 to 3 and Comparative Examples 1 to 3 were examined for the presence or absence of short circuits. The short circuit rate (%) was calculated by counting the number of short circuits among the 100 samples. The results are shown in Table 1. For Examples 1 to 3 and Comparative Examples 1 to 3, if the short circuit rate was 10% or less, it was judged as pass "◯", if the short circuit rate was 15% or less it was judged as somewhat good "△", and if the short circuit rate was more than 15%, it was judged as fail "×". Examples 1 to 3 and Comparative Example 1 were judged as pass "◯", while Comparative Examples 2 and 3 were judged as fail "×". This is because in Examples 1 to 3 and Comparative Example 1, the amount of CO2 generated between 550°C and 700°C was 53 mg / cm 3 The amount of CO2 generated between 550°C and 750°C was 155 mg / cm 3 This is thought to be because: [Table 1]

[0060] For each of Examples 1 to 3 and Comparative Examples 1 to 3, a cut was made to cause an initial defect, and then charging and discharging were performed, and it was determined whether CO2 could be detected by a CO2 detector during charging and discharging. The CO2 detector used was a carbon dioxide concentration measuring instrument CD-1000 manufactured by GASTEC. For Examples 1 to 3 and Comparative Examples 1 to 3, if CO2 was detected it was judged as passing (good), and if CO2 was not detected it was judged as failing (bad). The results are shown in Table 1. Examples 1 to 3 and Comparative Examples 2 and 3 were judged as passing (good), and Comparative Example 1 was judged as failing (bad). This is because in Examples 1 to 3 and Comparative Examples 2 and 3, the amount of CO2 generated between 550°C and 700°C was 30 mg / cm3. 3 The amount of CO2 generated between 550℃ and 750℃ was 90mg / cm 3 It is thought that this was because of the above.

[0061] For Examples 1 to 3 and Comparative Examples 1 to 3, if neither the short circuit rate nor the CO2 detection was a failure "x", the overall judgment was a pass "o". If at least one of the short circuit rate and the CO2 detection was a failure "x", the overall judgment was a failure "x". The results are shown in Table 1. While all of Comparative Examples 1 to 3 were a failure "x", all of Examples 1 to 3 were a pass "o". This is because the amount of CO2 generated from 550°C to 700°C in Examples 1 to 3 was 53 mg / cm 3 The amount of CO2 generated between 550°C and 750°C was 155 mg / cm 3 The amount of CO2 generated between 550°C and 700°C is less than 30 mg / cm 3 The amount of CO2 generated between 550℃ and 750℃ was 90mg / cm 3 It is thought that this was because of the above.

[0062] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0063] 10 1st internal electrode 11 First current collector layer 20 Second internal electrode 21 Second current collector layer 30 Solid electrolyte layer 31 void 40a First external electrode 40b 2nd external electrode 50 cover layers 51 Solid electrolyte green sheet 52 Internal electrode paste 53 Reverse pattern 54 Cover Sheet 55 External electrode paste 60 stacked chips 100,100a solid state battery

Claims

1. An all-solid-state battery comprising: a solid electrolyte layer; a first electrode layer provided on a first main surface of the solid electrolyte layer and including an electrode active material; and a second electrode layer provided on a second main surface of the solid electrolyte layer and including an electrode active material, When heated at a temperature rising rate of 20°C / min, the unit volume (cm ３ ) 30 mg to 53 mg of CO between 550 °C and 700 °C ２ is generated externally, and 90 mg to 155 mg of CO is generated between 550 °C and 750 °C. ２ An all-solid-state battery characterized by the external generation of

2. The solid electrolyte layer has CO ２ The all-solid-state battery according to claim 1, further comprising a void containing

3. 3. The all-solid-state battery according to claim 1, wherein the thickness of the solid electrolyte layer is 5 μm or more and 30 μm or less.

4. When a charge / discharge test is performed on the all-solid-state battery according to any one of claims 1 to 3, CO is released from the all-solid-state battery to the outside. ２ and evaluating the all-solid-state battery by detecting the

Images