All-solid-state batteries

Abstract

This all-solid-state battery is characterized by comprising: a multilayer body which is obtained by stacking a plurality of positive electrode layers each containing a positive electrode active material, a plurality of solid electrolyte layers and a plurality of negative electrode layers each containing a negative electrode active material, and which has a first surface where one of the positive electrode layers is exposed and a second surface where one of the negative electrode layers is exposed; a first external electrode which is provided on the first surface and is connected to the positive electrode layer; and a second external electrode which is provided on the second surface and is connected to the negative electrode layer. This all-solid-state battery is also characterized in that the number of the positive electrode layers is different from the number of the negative electrode layers.　

Description

Technical Field

[0001] The present invention relates to all-solid-state batteries.

Background Art

[0002] In recent years, secondary batteries have been used in various fields. Although secondary batteries using an electrolyte solution have problems such as leakage of the electrolyte solution, all-solid-state batteries in which the electrolyte and other components are also made of solids have the advantage of having no problem of liquid leakage (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, small all-solid-state batteries mounted on a wiring board or the like have a small capacity, and there is room for improvement in increasing the capacity.

[0005] The present invention has been made in view of the above problems, and an object thereof is to increase the capacity of an all-solid-state battery.

Means for Solving the Problems

[0006] The all-solid-state battery according to the present invention includes a laminate in which a plurality of positive electrode layers each containing a positive electrode active material, a solid electrolyte layer, and negative electrode layers each containing a negative electrode active material are laminated, and the laminate includes a first surface on which the positive electrode layer is exposed and a second surface on which the negative electrode layer is exposed, a first external electrode provided on the first surface and connected to the positive electrode layer, and a second external electrode provided on the second surface and connected to the negative electrode layer, and the number of layers of the positive electrode layer is different from the number of layers of the negative electrode layer.

[0007] In the all-solid-state battery described above, when the positive electrode capacity determined by the ratio of the positive electrode active material in the positive electrode layer and the theoretical capacity per unit weight of the positive electrode active material is larger than the negative electrode capacity determined by the ratio of the negative electrode active material in the negative electrode layer and the theoretical capacity per unit weight of the negative electrode active material, the number of layers of the negative electrode layer may be larger than the number of layers of the positive electrode layer. When the positive electrode capacity is smaller than the negative electrode capacity, the number of layers of the negative electrode layer may be smaller than the number of layers of the positive electrode layer.

[0008] In the all-solid-state battery described above, a plurality of layers of either the positive electrode layer or the negative electrode layer and one layer of the other may be alternately stacked in multiple layers.

[0009] In the all-solid-state battery described above, each of the plurality of layers may be thinner than the one layer of the other.

[0010] In the all-solid-state battery described above, the laminate may have a third surface different from each of the first surface and the second surface and parallel to each of the positive electrode layer and the negative electrode layer, and may further include a cover layer covering the third surface and a marker provided on the cover layer for distinguishing the first external electrode and the second external electrode.

[0011] In the all-solid-state battery described above, the first interval between the marker and the first external electrode and the second interval between the marker and the second external electrode may be different.

[0012] In the all-solid-state battery described above, the shape of the marker may be asymmetric with respect to a straight line perpendicular to the direction from the first external electrode to the second external electrode.

Advantages of the Invention

[0013] According to the present invention, the capacity of the all-solid-state battery can be increased.

Brief Description of the Drawings

[0014] [Figure 1] It is a schematic cross-sectional view showing the basic structure of an all-solid-state battery. [Figure 2] This is a top view of a solid-state battery. [Figure 3] This is a cross-sectional view of the laminate before the formation of the first and second external electrodes. [Figure 4] This is a cross-sectional view of a laminate where the number of negative electrode layers is greater than the number of positive electrode layers. [Figure 5] This is a cross-sectional view of a laminate with two negative electrode layers paired together. [Figure 6] This is a cross-sectional view of a laminated structure with two positive electrode layers paired together. [Figure 7] This is a top view showing another example of a solid-state battery. [Figure 8] This is a top view showing another example of an all-solid-state battery. [Figure 9] This is a flowchart of the manufacturing method for an all-solid-state battery according to this embodiment. [Modes for carrying out the invention]

[0015] The embodiments will be described below with reference to the drawings. (Embodiment) Figure 1 is a schematic cross-sectional view showing the basic structure of an all-solid-state battery 100. As shown in Figure 1, the all-solid-state battery 100 has a laminate 60 formed by stacking multiple solid electrolyte layers 11, positive electrode layers 12, and negative electrode layers 14. In the laminate 60, the solid electrolyte layer 11 is interposed between the positive electrode layer 12 and the negative electrode layer 14.

[0016] Of these, the positive electrode layer 12 is formed by laminating a first electrode layer 12c onto both main surfaces of the first current collector layer 12b, which is made of a conductive material. The material of the first electrode layer 12c is not particularly limited as long as it is a conductive layer containing a positive electrode active material. Here, a material having an olivine-type crystal structure is used as the positive electrode active material. For example, such a positive electrode active material is a phosphate containing a transition metal and lithium. The olivine-type crystal structure is the crystal structure found in natural olivine and can be identified by X-ray diffraction.

[0017] Examples of electrode active materials with an olivine-type crystal structure include LiCoPO4 containing Co. Phosphates in which the transition metal Co is replaced in this chemical formula may also be used. Here, the ratio of Li and PO4 may vary depending on the valency. Note that Co, Mn, Fe, Ni, etc. may be used as the transition metal.

[0018] Furthermore, the negative electrode layer 14 is formed by laminating a second electrode layer 14c onto both main surfaces of a second current collector layer 14b made of a conductive material. The material of the second electrode layer 14c is not particularly limited as long as it is a conductive layer containing a negative electrode active material. Here, titanium oxide, lithium titanium composite oxide, lithium titanium composite phosphate, carbon, and lithium vanadium phosphate are used as the negative electrode active material.

[0019] Furthermore, the second electrode layer 14c may contain an electrode active material having an olivine-type crystal structure. This can increase the discharge capacity or raise the operating potential associated with discharge.

[0020] Furthermore, when fabricating the first electrode layer 12c and the second electrode layer 14c, oxide-based solid electrolyte materials and conductive additives such as carbon and metals may be added to these electrode layers. Examples of conductive additive metals include Pd, Ni, Cu, and Fe. In addition, alloys of these metals may be used as conductive additives.

[0021] In this example, the positive electrode layer 12 is composed of a first current collector layer 12b and two layers of the first electrode layer 12c, but the positive electrode layer 12 may also be composed of only a single layer of the first current collector layer 12b containing the positive electrode active material. Similarly, the negative electrode layer 14 may be composed of only a single layer of the second current collector layer 14b containing the negative electrode active material.

[0022] On one hand, as the material of the solid electrolyte layer 11, there is, for example, a phosphate-based solid electrolyte having a NASICON structure. The phosphate-based solid electrolyte having a NASICON structure has high ionic conductivity and is chemically stable in the atmosphere. The phosphate-based solid electrolyte is not particularly limited, but here, a phosphate containing lithium is used. The phosphate is, for example, a composite lithium phosphate salt with Ti (LiTi2(PO4)3) as a base, and is a salt in which a part is substituted with a trivalent transition metal such as Al, Ga, In, Y, La, etc. to increase the Li content. Such salts include Li 1+x Al x Ge 2-x (PO4)3, Li 1+x Al x Zr 2-x (PO4)3, and Li 1+x Al x Ti 2-x (PO4)3 and other Li-Al-M-PO4-based phosphates (M is Ge, Ti, Zr, etc.).

[0023] Also, a Li-Al-Ge-PO4-based phosphate in which a transition metal contained in the phosphate in the first electrode layer 12c is added in advance may be used as the material of the solid electrolyte layer 11. For example, when the first electrode layer 12c contains a phosphate containing either Co or Li, a Li-Al-Ge-PO4-based phosphate added with Co in advance may be contained in the solid electrolyte layer 11. Thereby, elution of the transition metal from the first electrode layer 12c to the solid electrolyte layer 11 can be suppressed.

[0024] Such a laminate 60 has a first surface 60a and a second surface 60b parallel to the stacking direction Z of the positive electrode layer 12 and the negative electrode layer 14. Among these, the solid electrolyte layer 11 and the positive electrode layer 12 are exposed on the first surface 60a. A first external electrode 40a is further provided on the first surface 60a, and the positive electrode layer 12 is connected to the first external electrode 40a.

[0025] On the other hand, the second surface 60b is opposite the first surface 60a, and the solid electrolyte layer 11 and the negative electrode layer 14 are exposed. A second external electrode 40b is provided on the second surface 60b, and the negative electrode layer 14 is connected to the second external electrode 40b.

[0026] Furthermore, the laminate 60 has a third surface 60c and a fourth surface 60d parallel to the positive electrode layer 12 and the negative electrode layer 14, respectively. The third surface 60c is the upper surface that faces upward when the all-solid-state battery 100 is mounted on the wiring board. The fourth surface 60d is the lower surface that faces downward when mounted.

[0027] In this example, a cover layer 19 is formed on the third surface 60c and the fourth surface 60d, respectively, to protect the positive electrode layer 12 and the negative electrode layer 14 from the atmosphere. The material of the cover layer 19 is not particularly limited, but the same material as the solid electrolyte layer 11 can be used for the cover layer 19.

[0028] In this embodiment, a visible marker 70 is provided on the cover layer 19 to distinguish between the first external electrode 40a and the second external electrode 40b. The thickness of the marker 70 is not particularly limited, but in this embodiment, for example, it is about 5 μm to 20 μm. This makes it possible to suppress cracking or peeling of the marker 70 when the marker 70 is fired. The marker 70 may be connected to either the first external electrode 40a or the second external electrode 40b, or it may not be connected to both external electrodes 40a and 40b.

[0029] Furthermore, in order to make the marker 70 easily recognizable by visual inspection or camera, it is preferable to make the marker 70 a different color from the cover layer 19. For example, if the cover layer 19 is white, adding carbon to the marker 70 to make it black will create a clear difference in brightness between the marker 70 and the cover layer 19, making it easy to see the marker 70 with a camera or by visual inspection. However, if the marker 70 is visible without adding carbon, it is not necessary to add carbon to the marker 70. In this example, the marker 70 is made of a material different from both the cover layer 19 and the external electrodes 40a and 40b. The marker 70 may also be formed of a material different from that of the positive electrode layer 12 and the negative electrode layer 14, respectively.

[0030] Alternatively, by forming the marker 70 with the same material as the positive electrode layer 12 and the negative electrode layer 14, the development costs for new materials for the marker 70 can be reduced, thereby suppressing the cost increase of the all-solid-state battery 100. Furthermore, the marker 70 may be formed with materials different from those used for the positive electrode layer 12 and the negative electrode layer 14, respectively. Figure 2 is a top view of the all-solid-state battery 100. As shown in Figure 2, in this embodiment, the marker 70 is positioned close to the first external electrode 40a in a top view, thereby indicating the first external electrode 40a. In this case, the distance L1 between the first external electrode 40a and the marker 70 is shorter than the distance L2 between the second external electrode 40b and the marker 70. Note that the marker 70 may be moved further away from each of the external electrodes 40a and 40b by setting the distances L1 and L2 to values ​​greater than 0.

[0031] Furthermore, the shape of the marker 70 is a rectangle symmetrical with respect to a straight line P perpendicular to the direction X from the first external electrode 40a to the second external electrode 40b.

[0032] Figure 3 is a cross-sectional view of the laminate 60 before the formation of the first external electrode 40a and the second external electrode 40b. As shown in Figure 3, in this embodiment, the negative electrode layer 14 has n layers, while the positive electrode layer 12 has n+1 layers, meaning that the number of layers in the positive electrode layer 12 and the negative electrode layer 14 are different. This allows for a larger positive electrode layer 12 and thus a larger capacity for the all-solid-state battery 100 compared to the case where the number of layers in the positive electrode layer 12 is the same as the negative electrode layer 14, which is n layers.

[0033] However, if the number of positive electrode layers 12 is increased indiscriminately, the capacitance of the positive electrode side will become too large compared to that of the negative electrode side, resulting in a capacitance imbalance between the positive and negative electrodes. To avoid this, the number of positive electrode layers 12 or negative electrode layers 14 to be increased should be determined based on the theoretical capacitance value, as follows.

[0034] First, let the theoretical capacity per unit weight of the positive electrode active material be c p (Ah / g), the density of the positive electrode active material is ρ p (g / cm 3 ) Also, the thickness of the positive electrode layer 12 is T p (cm), area S p (cm 2 ) Furthermore, the ratio of the area occupied by the positive electrode active material in the positive electrode layer 12 is A p (%). At this time, the positive electrode capacitance C per positive electrode layer 12 is p (Ah / g) is c p ×ρ p ×T p ×S p ×A p This is the result. Note that the thickness T of the positive electrode layer 12. p While not particularly limited, it is, for example, 10 μm to 20 μm. Note that ratio A p This can be calculated by observing a cross-section of the positive electrode layer 12 parallel to the stacking direction Z (see Figure 1) using SEM (Scanning Electron Microscope)-EDS (Energy Dispersive X-ray Spectroscopy) mapping and identifying the proportion of elements specific to the positive electrode active material that occupy that cross-section.

[0035] Similarly, the theoretical capacity per unit weight of the negative electrode active material is c n (Ah / g), the density of the negative electrode active material is ρ n (g / cm 3 ) Also, the thickness of the negative electrode layer 14 is T n (cm), area S n (cm 2 ) Furthermore, the ratio of the area occupied by the negative electrode active material in the negative electrode layer 14 is A n (%). At this time, the negative electrode capacitance C per single negative electrode layer 14 is n (Ah / g) is c n ×ρ n ×T n ×S n ×A n This is the result. Note that the thickness T of the negative electrode layer 14. n While not particularly limited, it is, for example, 10 μm to 20 μm. Note that ratio A n This can be calculated by observing the cross-section of the negative electrode layer 14 parallel to the stacking direction Z (see Figure 1) using SEM-EDS mapping, and identifying the proportion of elements specific to the negative electrode active material that occupy that cross-section.

[0036] The positive electrode capacitance C was determined in this way. p The negative electrode capacitance C n If the value is smaller than the given value, the difference in capacitance between the positive and negative electrodes can be reduced by decreasing the number of negative electrode layers 14 compared to the number of positive electrode layers 12, as shown in Figure 3, thereby reducing the capacitance imbalance between the positive and negative electrodes.

[0037] On the other hand, positive electrode capacitance C p The negative electrode capacitance C n If the value is greater than the given value, the difference in capacitance between the positive and negative electrodes can be reduced by increasing the number of negative electrode layers 14 compared to the number of positive electrode layers 12, thereby reducing the capacitance imbalance between the positive and negative electrodes. Figure 4 is a cross-sectional view of the laminate 60 when the number of negative electrode layers 14 is greater than the number of positive electrode layers 12.

[0038] Furthermore, the positive electrode capacitance C of all positive electrode layers 12 p Total value C p_all And the negative electrode capacitance C of all negative electrode layers 14 n Total value Cn_all The number of layers in the positive electrode layer 12 and the negative electrode layer 14 can be adjusted so that the difference ΔC is as small as possible. For example, if ΔC is C p_all The capacitance imbalance between the positive and negative electrode sides may be reduced by adjusting the number of layers in the positive electrode layer 12 and the negative electrode layer 14 so that the imbalance is ±15% or less, more preferably ±5% or less.

[0039] Furthermore, if the number of positive electrode layers 12 is greater than the number of negative electrode layers 14, it is possible to provide the effect of improving the capacity change during repeated charging and discharging, also known as the charge-discharge cycle characteristics.

[0040] However, if the marker 70 is formed on the cover layer 19 as in this embodiment, the marker 70 will be exposed, and may peel off due to external impacts or the like. When this happens, the marker 70 cannot be seen by camera or visual inspection, and it becomes impossible to distinguish between the first external electrode 40a and the second external electrode 40b.

[0041] Even if the marker 70 peels off in this way, as long as the external electrodes 40a and 40b are not yet formed, the polarity can be distinguished by visually observing the difference in the number of layers of the positive electrode layer 12 exposed on the first surface 60a and the number of layers of the negative electrode layer 14 exposed on the second surface 60b, by a person or camera.

[0042] In the examples shown in Figures 3 and 4, the positive electrode layer 12 and the negative electrode layer 14 are stacked alternately in one layer each, but this embodiment is not limited to this. Figure 5 is a cross-sectional view of the laminate 60 when two negative electrode layers 14 are paired. In this case, two negative electrode layers 14 and one positive electrode layer 12 are stacked alternately. As a result, when the number of layers in the positive electrode layer 12 is n, the number of layers in the negative electrode layer 14 becomes twice that, 2n layers. Therefore, the difference in the number of layers of the positive electrode layer 12 exposed on the first surface 60a and the number of layers of the negative electrode layer 14 exposed on the second surface 60b is larger than in the case of Figure 4. Consequently, it becomes easier for people and cameras to distinguish the difference in the number of layers between the positive electrode layer 12 and the negative electrode layer 14, making it easier to determine the polarity of the all-solid-state battery 100.

[0043] In this case, it is preferable to make the negative electrode layer 14 thinner than the positive electrode layer 12. For example, the thickness T of the positive electrode layer 12 p If the thickness is 20 μm to 30 μm, then the thickness T of the negative electrode layer 14 n It is preferable to set the thickness to 5 μm to 10 μm. This prevents the negative electrode layer 14, which has more layers than the positive electrode layer 12, from having an excessively large capacitance on the negative electrode side compared to the positive electrode side, thus preventing an imbalance in the cell.

[0044] Furthermore, while the example in Figure 5 uses two negative electrode layers 14 paired together, two positive electrode layers 12 may also be paired together, as shown in the cross-sectional view in Figure 6. Additionally, three or more positive electrode layers 12 and one negative electrode layer 14 may be alternately stacked, or three or more negative electrode layers 14 and one positive electrode layer 12 may be alternately stacked.

[0045] Figure 7 is a top view showing another example of an all-solid-state battery. In the example in Figure 7, the marker 70 points to the second external electrode 40b by making the spacing L2 smaller than the spacing L1.

[0046] Figure 8 is a top view showing another example of an all-solid-state battery. In the example in Figure 8, a triangular marker 70 is placed approximately in the center of the all-solid-state battery 100 in a top view. The vertex 70a of the marker 70 is pointed towards the first external electrode 40a, thereby indicating the first external electrode 40a with the marker 70.

[0047] In this case, the shape of the marker 70 is asymmetric with respect to a straight line P perpendicular to the direction X from the first external electrode 40a to the second external electrode 40b. This asymmetry allows a person or camera to distinguish between the first external electrode 40a and the second external electrode 40b.

[0048] As described above, in this embodiment, as shown in Figure 3, the number of layers in the positive electrode layer 12 is made n+1 and the number of layers in the negative electrode layer 14 is made n, so that the number of layers in the positive electrode layer 12 and the negative electrode layer 14 are different. Therefore, compared to the case where both the positive electrode layer 12 and the negative electrode layer 14 have n layers, the number of layers in the positive electrode layer 12 is increased, and the capacity of the all-solid-state battery 100 can be increased.

[0049] Furthermore, since the all-solid-state battery 100 is equipped with a marker 70, the first external electrode 40a and the second external electrode 40b can be distinguished by visually inspecting the marker 70 using a camera or by eye. Therefore, it is possible to prevent the all-solid-state battery 100 from being mounted on the wiring board with the opposite polarity, thereby preventing malfunctions and overheating accidents in electronic devices.

[0050] Furthermore, even if the marker 70 peels off due to impact or the like, the polarity of the all-solid-state battery 100 can be determined by a camera or a person recognizing the difference between the number of layers of the positive electrode layer 12 exposed on the first surface 60a and the number of layers of the negative electrode layer 14 exposed on the second surface 60b.

[0051] Next, the method for manufacturing the all-solid-state battery according to this embodiment will be described. Figure 9 is a flowchart of the method for manufacturing the all-solid-state battery according to this embodiment.

[0052] (Ceramic raw material powder production process) First, a powder of the phosphate-based solid electrolyte constituting the solid electrolyte layer 11 is prepared. For example, the powder of the phosphate-based solid electrolyte constituting the solid electrolyte layer 11 can be prepared by mixing raw materials and additives and using a solid-phase synthesis method. The obtained powder can be adjusted to the desired average particle size by dry grinding. For example, the desired average particle size can be adjusted using a planetary ball mill with 5 mmφ ZrO2 balls.

[0053] The additives include sintering aids. As sintering aids, for example, any of the glass components of Li-BO, Li-Si-O, Li-CO, Li-SO, and Li-PO compounds may be used.

[0054] (Green sheet manufacturing process) Next, the obtained powder is uniformly dispersed in an aqueous solvent or organic solvent together with a binder, dispersant, and plasticizer, etc., and wet grinding is performed to obtain a solid electrolyte slurry having the desired average particle size. At this time, a bead mill, wet jet mill, various kneaders, high-pressure homogenizer, etc. can be used, and a bead mill is preferred from the viewpoint that particle size distribution adjustment and dispersion can be performed simultaneously.

[0055] Then, a binder is added to the obtained solid electrolyte slurry to obtain a solid electrolyte paste. By coating with the solid electrolyte paste, a green sheet for the solid electrolyte layer 11 is obtained. A green sheet for the cover layer 19 can be prepared in the same manner. The coating method is not particularly limited, and methods such as slot die method, reverse coat method, gravure coat method, bar coat method, and doctor blade method can be used. The particle size distribution after wet grinding can be measured, for example, using a laser diffraction measuring device that employs laser diffraction scattering.

[0056] (Process for preparing electrode layer paste) Next, an electrode layer paste is prepared for creating the first electrode layer 12c and the second electrode layer 14c. For example, the electrode active material and solid electrolyte material are highly dispersed using a bead mill or the like to produce a ceramic paste consisting only of ceramic particles. Alternatively, a carbon paste containing carbon particles such as carbon black may be prepared and mixed with the ceramic paste.

[0057] (Process for preparing paste for current collectors) Next, a current collector paste is prepared for creating the first current collector layer 12b and the second current collector layer 14b described above. For example, a current collector paste can be obtained by uniformly dispersing Pd powder, a binder, a dispersant, and a plasticizer in water or an organic solvent.

[0058] (Marker paste preparation process) Next, a marker paste is prepared for making the marker 70 described above. Here, the marker paste is prepared by kneading carbon particles such as carbon black with ceramic particles.

[0059] (Lamination process) First, electrode layer paste, current collector paste, and electrode layer paste are printed on one main surface of a green sheet in that order. Next, a laminate 60 is obtained by stacking multiple printed green sheets alternately with a slight offset. Then, multiple green sheets for the cover layer 19 are stacked on the third surface 60c and the fourth surface 60d of the laminate 60, and paste for the marker 70 is printed on the topmost green sheet.

[0060] (Firing process) Next, the laminate 60 is fired in a firing atmosphere containing oxygen. To suppress the loss of carbon material contained in the electrode layer paste, the oxygen partial pressure of the firing atmosphere is set to 2 × 10⁻⁶. -13 It is preferable to keep the oxygen partial pressure below atm. On the other hand, in order to suppress the melting of phosphate-based solid electrolytes, the oxygen partial pressure should be 5 × 10⁻⁶. -22 It is preferable to set it to atm or higher.

[0061] Subsequently, metal paste is applied to each surface 60a and 60b of the laminate 60 and baked to form the first external electrode 40a and the second external electrode 40b. Alternatively, the first external electrode 40a and the second external electrode 40b may be formed by sputtering or plating. With this, the basic structure of the all-solid-state battery 100 is completed. [Examples]

[0062] A solid-state battery was fabricated according to the following embodiment, and its characteristics were investigated.

[0063] (Example 1) Co3O4, Li2CO3, ammonium dihydrogen phosphate, Al2O3, and GeO2 are mixed to form a solid electrolyte material powder containing a predetermined amount of Co. 1.3 Al 0.3 Ge 1.7(PO4)3 was prepared by solid-phase synthesis. The obtained powder was pulverized to prepare a solid electrolyte slurry. A binder was added to the obtained slurry to obtain a solid electrolyte paste, and a green sheet was prepared. LiCoPO4, Li containing a predetermined amount of Co. 1.3 Al 0.3 Ti 1.7 (PO4)3 was synthesized by solid-phase synthesis in the same manner as described above, and a slurry was prepared by wet mixing and dispersion. A binder and Pd paste were then added to prepare a paste for the electrode layer.

[0064] On a green sheet, electrode layer paste, current collector paste, and electrode layer paste were each printed to a thickness of 2 μm using screen printing. Five of the printed green sheets were stacked, offset so that the electrodes were pulled out to the left and right, to create a laminate 60. Three of the five green sheets were for the positive electrode layer 12, and the remaining two were for the negative electrode layer 14.

[0065] Multiple green sheets were attached to the top and bottom of the laminate 60 as cover layers 19. Furthermore, a marker 70 was printed on the top layer of green sheet. After that, the green sheets were pressed together using a heat press, and the laminate 60 was cut to the specified size using a dicer.

[0066] The cut laminated material 60 was degreased by heat treatment at 300°C to 500°C, and then sintered by heat treatment at 900°C or lower.

[0067] (Example 2) Of the five green sheets, two were used for the positive electrode layer 12, and the remaining three were used for the negative electrode layer 14. All other aspects were the same as in Example 1.

[0068] (Example 3) A laminate 60 was fabricated by stacking nine green sheets. Three of the nine green sheets were used for the positive electrode layer 12, and the remaining six were used for the negative electrode layer 14. Furthermore, by stacking two of the six green sheets for the negative electrode layer 14, a structure was obtained in which two negative electrode layers 14 and one positive electrode layer 12 were alternately stacked, as shown in Figure 5. The rest of the procedure was the same as in Example 1.

[0069] (Comparative Example 1) A laminate 60 was fabricated by stacking four green sheets. Two of the four green sheets were used as the positive electrode layer 12, and the remaining two were used as the negative electrode layer 14. All other aspects were the same as in Example 1.

[0070] Next, the capacity of the all-solid-state batteries was investigated for Examples 1-3 and Comparative Example 1. Furthermore, it was investigated whether the polarity of the all-solid-state battery could be determined by the difference in the number of layers of the positive electrode layer 12 exposed on the first surface 60a and the number of layers of the negative electrode layer 14 exposed on the second surface 60b when the marker 70 peeled off. The results are shown in Table 1.

[0071] [Table 1] In Table 1, "the larger of the positive electrode capacity and the negative electrode capacity" is the positive electrode capacity C mentioned above. p and negative electrode capacitance C n This indicates which of the two is larger. Furthermore, for "polarity determination by appearance," a "○" is used if the polarity can be determined based on the difference between the number of layers of the positive electrode layer 12 exposed on the first surface 60a and the number of layers of the negative electrode layer 14 exposed on the second surface 60b, and a "×" is used if this is not possible.

[0072] The "capacity" was calculated as follows: First, the discharge capacity Q (mAh) at A-0.5(V) was measured. Next, charging was performed with a constant current I, and the voltage change ΔV between each external electrode 40a and 40b immediately after the start of charging was measured. The value obtained by multiplying the resistance R (=ΔV / I) by the discharge capacity Q was taken as the capacity C (mAh·Ω). If the capacity C was 2500mAh·Ω or more, it was marked "○", if the capacity C was 1000mAh·Ω or more but less than 2500, it was marked "△", and if the capacity C was less than 1000mAh·Ω, it was marked "×".

[0073] Furthermore, the "Overall Evaluation" was marked as "×" if at least one of "Polarity Discrimination by Appearance" or "Capacity" was marked as "×". Also, if neither "Polarity Discrimination by Appearance" nor "Capacity" was marked as "×", but neither of them was marked as "〇", the "Overall Evaluation" was marked as "△". Finally, if both "Polarity Discrimination by Appearance" and "Capacity" were marked as "〇", the "Overall Evaluation" was also marked as "〇".

[0074] As shown in Table 1, in all three examples (1-3), both "polarity determination by appearance" and "capacity" were rated "○", and the "overall evaluation" was also rated "○".

[0075] On the other hand, in Comparative Example 1, the number of layers in both the positive electrode layer 12 and the negative electrode layer 14 was the same, so the "polarity determination by appearance" was "×". Furthermore, in Comparative Example 1, the combined number of layers in both the positive electrode layer 12 and the negative electrode layer 14 was less than in Examples 1 to 3, resulting in a "△" for capacity. As a result, the "overall evaluation" of Comparative Example 1 was "×".

[0076] Although embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention as described in the claims. [Explanation of Symbols]

[0077] 11: Solid electrolyte layer 12: Positive electrode layer 14: Negative electrode layer 19: Cover layer 40a: First external electrode 40b: Second external electrode 60: Laminate 70: Marker 100: All-solid-state battery

Claims

1. A laminate comprising a plurality of positive electrode layers containing a positive electrode active material and a plurality of negative electrode layers containing a negative electrode active material, which are alternately laminated with a solid electrolyte layer in between, and having a first surface from which the plurality of positive electrode layers are drawn out and a second surface from which the plurality of negative electrode layers are drawn out, A first external electrode provided on the first surface and connected to the plurality of positive electrode layers, It has a second external electrode provided on the second surface and connected to the plurality of negative electrode layers, The number of layers in the negative electrode layer is greater than the number of layers in the positive electrode layer. An all-solid-state battery characterized in that the positive electrode capacity per positive electrode layer is greater than the negative electrode capacity per negative electrode layer.

2. The laminate has a third surface that is different from each of the first and second surfaces and is parallel to each of the positive electrode layer and the negative electrode layer. A cover layer covering the third surface, The all-solid-state battery according to claim 1, further comprising a marker provided on the cover layer for distinguishing the first external electrode from the second external electrode.

3. The all-solid-state battery according to claim 2, characterized in that the first distance between the marker and the first external electrode and the second distance between the marker and the second external electrode are different.

4. The all-solid-state battery according to claim 2, characterized in that the shape of the marker is asymmetrical with respect to a straight line perpendicular to the direction from the first external electrode to the second external electrode.

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