JP2024066801A - All-solid-state battery - Google Patents

Abstract

[Problem] To provide an all-solid-state battery capable of suppressing the occurrence of cracks. [Solution] The all-solid-state battery is an all-solid-state battery having a length L, and is characterized in that it comprises a laminated chip in which solid electrolyte layers and internal electrodes containing an electrode active material are alternately laminated to have a substantially rectangular parallelepiped shape, and in which the laminated internal electrodes are alternately exposed at two opposing end faces, and a first external electrode and a second external electrode provided on the two end faces, and in which, when the distances over which the first external electrode and the second external electrode extend in the direction of the length L are distances E1 and E2, respectively, 0.5L≦(E1+E2)≦0.8L is satisfied. [Selected Figure] Figure 5

Description

The present invention relates to an all-solid-state battery.

Stacked solid-state batteries are safe and easy to handle secondary batteries, as they do not pose the risk of fire or leakage and can be reflow soldered (see, for example, Patent Documents 1 to 4). A shift from lithium-ion batteries that use conventional electrolytes is being considered, and it is expected that they will be used in a wide range of fields.

International Publication No. 2018/186449 International Publication No. 2020/070989 International Publication No. 2021/070927 JP 2017-182945 A

However, there is a risk of cracks occurring in solid-state batteries when bending stress is applied.

The present invention has been developed in consideration of the above problems, and aims to provide an all-solid-state battery that can suppress the occurrence of cracks.

The all-solid-state battery according to the present invention is an all-solid-state battery having a length L, and is characterized in that it is provided with a laminated chip in which solid electrolyte layers and internal electrodes containing an electrode active material are alternately laminated to have a substantially rectangular parallelepiped shape, and in which the laminated internal electrodes are alternately exposed on two opposing end faces, and a first external electrode and a second external electrode provided on the two end faces, and in which, when the distances over which the first external electrode and the second external electrode extend in the direction of the length L are distances E1 and E2, respectively, 0.5L≦(E1+E2)≦0.8L is satisfied.

In the above all-solid-state battery, distance E1 and distance E2 may each be 0.15 L or more and 0.65 L or less.

In the above all-solid-state battery, the thickness of the first external electrode and the second external electrode may be 10 μm or more and 200 μm or less.

In the above all-solid-state battery, the main component of the first external electrode and the second external electrode may be Ag (silver), Cu (copper), Ni (nickel), Pd (palladium), C (carbon), Al (aluminum), or Au (gold).

The present invention provides an all-solid-state battery that can suppress the occurrence of cracks.

FIG. 1 is a schematic cross-sectional view showing a basic structure of an all-solid-state battery. FIG. 1 is an external view of a stacked-type all-solid-state battery in which a plurality of battery units are stacked. FIG. 1 is a schematic cross-sectional view of a stacked type all-solid-state battery. FIG. 2 is a schematic cross-sectional view of another stacked type all-solid-state battery. FIG. 4 is a diagram illustrating the dimensions of each part. FIG. 4 is a diagram illustrating the dimensions of each part. 10A and 10B are diagrams for explaining a method for measuring the thickness of an external electrode. FIG. 1 is a diagram illustrating a flow of a method for producing an all-solid-state battery. 1A and 1B are diagrams illustrating a lamination process.

The following describes the embodiment with reference to the drawings.

(Embodiment)
Fig. 1 is a schematic cross-sectional view showing the basic structure of an all-solid-state battery 200. As illustrated in Fig. 1, the all-solid-state battery 200 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. For example, the first internal electrode 10, the second internal electrode 20, and the solid electrolyte layer 30 are sintered bodies obtained by sintering powder materials.

When the all-solid-state battery 200 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.

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. The phosphate-based solid electrolyte having a NASICON-type crystal structure has a high electrical 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 thereof include a composite lithium phosphate with Ti (for example, LiTi ₂ (PO ₄ ) ₃ ). Alternatively, Ti can be partially or completely replaced with a tetravalent transition metal such as Ge, Sn, Hf, or Zr. In order to increase the Li content, it may be partially replaced 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 (PO ₄ ) ₃ , Li _1+x Al _x Zr _2-x (PO ₄ ) ₃ , Li _1+x Al _x Ti _2-x (PO ₄ ) ₃ , etc. are listed. For example, Li-Al-Ge-PO 4 based material to which the same transition metal as the transition metal contained in the phosphate having an olivine type crystal structure contained in the first internal electrode 10 and the second internal electrode 20 is added in advance is preferable. For example, when the first internal electrode 10 and the second internal electrode 20 contain a phosphate containing Co and Li, it is _preferable that the Li-Al-Ge-PO ₄ based material to which Co is added in advance is contained in the solid electrolyte layer 30. In this case, the effect of suppressing the elution of the transition metal contained in the electrode active material into the electrolyte is obtained. When the first internal electrode 10 and the second internal electrode 20 contain a phosphate containing a transition element other than Co and Li, it is preferable that the solid electrolyte layer 30 contains a Li-Al-Ge-PO ₄ based material to which the transition metal has been added in advance.

The first internal electrode 10 used as the 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 that natural olivine has, and can be identified by X-ray diffraction.

A typical example of an electrode active material having an olivine crystal structure is _LiCoPO4 containing Co. Phosphates in which the transition metal Co is replaced in this chemical formula can also be used. Here, the ratio of Li and _PO4 can vary depending on the valence. Note that it is preferable to use Co, Mn, Fe, Ni, etc. as the transition metal.

The electrode active material having an olivine crystal structure acts as a positive electrode active material in the first internal electrode 10 acting as a positive electrode. For example, when only the first internal electrode 10 contains an electrode active material having an olivine 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 crystal structure, the second internal electrode 20 acting 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.

When both the first internal electrode 10 and the second internal electrode 20 contain an electrode active material having an olivine crystal structure, each electrode active material preferably contains a transition metal that may be the same or different from each other. "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 may contain 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 may contain 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. If the first internal electrode 10 and the second internal electrode 20 contain the same type of transition metal or contain an electrode active material of the same composition, the similarity of the compositions of the two internal electrode layers is increased, so that even if the terminals of the all-solid-state battery 200 are attached in the opposite direction, it has the effect of being able to withstand practical use without malfunction depending on the application.

The second internal electrode 20 contains a negative electrode active material. By containing the negative electrode active material in only one electrode, it becomes clear that the one electrode acts as a negative electrode and the other electrode acts as a positive electrode. It is also possible to contain a substance that is known as a negative electrode active material in both electrodes. For the negative electrode active material of the electrode, reference can be made to conventional techniques in secondary batteries as appropriate, and examples of the compound include titanium oxide, lithium titanium composite oxide, lithium titanium composite phosphate, carbon, and lithium vanadium phosphate.

In the preparation 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 and a conductive material (conductive assistant) are added. For these components, a paste for the internal electrodes can be obtained by uniformly dispersing a binder and a plasticizer in water or an organic solvent. The conductive assistant may contain a carbon material or the like. The conductive assistant may contain a metal. Examples of the metal of the conductive assistant include Pd, Ni, Cu, Fe, and alloys containing these. The solid electrolyte contained in the first internal electrode 10 and the second internal electrode 20 may be the same as the main solid electrolyte of the solid electrolyte layer 30, for example.

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 thickness of 10 different points on one layer.

2 is an external view of a stacked type all-solid-state battery 100 in which a plurality of battery units are stacked, with the all-solid-state battery 200 being a battery unit. As illustrated in FIG. 2, the all-solid-state battery 100 includes a stacked chip 70 having a substantially rectangular parallelepiped shape, and a first external electrode 40a and a second external electrode 40b provided on either of two opposing end faces of the stacked chip 70. Of the four faces of the stacked chip 70 other than the two end faces, the two faces other than the upper and lower faces in the stacking direction are referred to as side faces. The first external electrode 40a and the second external electrode 40b extend to the upper, lower and two side faces in the stacking direction of the stacked chip 70. However, the first external electrode 40a and the second external electrode 40b are spaced apart from each other. The size of the all-solid-state battery 100 is, for example, 4.1 mm to 4.9 mm in length, 2.9 mm to 3.5 mm in width, and 2.9 mm to 3.5 mm in height, but is not limited to these sizes. The length is the length in the direction in which the first external electrode 40a and the second external electrode 40b face each other. The height is the height in the stacking direction.

Figure 3 is a cross-sectional view taken along line I-I in Figure 2. In the following description, components having the same composition range, thickness range, and particle size distribution range as the all-solid-state battery 200 are denoted by the same reference numerals and will not be described in detail.

In the all-solid-state battery 200, a plurality of first internal electrodes 10 and a plurality of second internal electrodes 20 are alternately stacked with a solid electrolyte layer 30 interposed therebetween. The edges of the plurality of first internal electrodes 10 are exposed to the first end face of the stacked chip 70, but are not exposed to the second end face. The edges of the plurality of second internal electrodes 20 are exposed to the second end face of the stacked chip 70, but are not exposed to the first end face. As a result, the first internal electrodes 10 and the second internal electrodes 20 are alternately conductive 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 100 has a structure in which a plurality of battery units are stacked.

A cover layer 50 is laminated on the upper surface of the laminate of the first internal electrode 10, the solid electrolyte layer 30, and the second internal electrode 20. The cover layer 50 is in contact with the uppermost internal electrode (either the first internal electrode 10 or the second internal electrode 20) and is in contact with a part of the solid electrolyte layer 30. A cover layer 50 is also laminated on the lower surface of the laminate. The cover layer 50 is in contact with the lowermost internal electrode (either the first internal electrode 10 or the second internal electrode 20) and is in contact with a part of the solid electrolyte layer 30. For example, the cover layer 50 is a sintered body obtained by sintering a powder material.

The first internal electrode 10 and the second internal electrode 20 may have a collector layer. For example, as illustrated in FIG. 4, a first collector layer 11 may be provided in the first internal electrode 10. A second collector layer 21 may be provided in the second internal electrode 20. The first collector layer 11 and the second collector layer 21 are mainly composed of a conductive material. For example, metal, carbon, etc. can be used as the conductive material of the first collector layer 11 and the second collector layer 21. The current collection efficiency is improved by connecting the first collector layer 11 to the first external electrode 40a and connecting the second collector layer 21 to the second external electrode 40b.

In a stacked-type all-solid-state battery such as the all-solid-state battery 100 in FIG. 3 or FIG. 4, cracks may occur when bending stress is applied. Therefore, in this embodiment, a configuration that can suppress the occurrence of cracks will be described.

As illustrated in FIG. 5, in the all-solid-state battery 100, the length in the direction in which the first external electrode 40a and the second external electrode 40b face each other is defined as length L. The extension distance of the first external electrode 40a on the upper surface, lower surface, and two side surfaces of the laminated chip 70 in the direction of length L is defined as distance E1. The extension distance of the second external electrode 40b on the upper surface, lower surface, and two side surfaces of the laminated chip 70 in the direction of length L is defined as distance E2. The distance E, which is the sum of the distances E1 and E2, satisfies the relationship of 0.5L≦distance E≦0.8L. By satisfying the relationship of 0.5L≦distance E, the first external electrode 40a and the second external electrode 40b are able to sufficiently wrap around the upper surface, lower surface, and two side surfaces of the laminated chip 70. As a result, the bending displacement of the all-solid-state battery 100 is suppressed by the first external electrode 40a and the second external electrode 40b, and the occurrence of cracks can be suppressed. As a result, it is possible to suppress the intrusion of moisture into the interior of the laminated chip 10. In addition, by satisfying the relationship of distance E≦0.8L, the distance between the first external electrode 40a and the second external electrode 40b becomes sufficiently large. This suppresses leakage current and suppresses deterioration of the cycle characteristics of the all-solid-state battery 100.

From the viewpoint of suppressing bending displacement of the all-solid-state battery 100, the distance E is preferably 0.5L or more, and more preferably 0.6L or more.

On the other hand, from the viewpoint of suppressing the occurrence of leakage current, it is preferable that the distance E is 0.8L or less, and more preferably 0.7L or less.

The distance E1 and the distance E2 may be equal to each other, and the first external electrode 40a and the second external electrode 40b may have a symmetrical shape. Or, as illustrated in FIG. 6, the distance E1 and the distance E2 may be different from each other, and the first external electrode 40a and the second external electrode 40b may have an asymmetrical shape. For example, as illustrated in FIG. 6, the distance E1 may be longer than the distance E2.

From the viewpoint of suppressing bending displacement of the all-solid-state battery 100, the distances E1 and E2 are each preferably 0.15L or more, more preferably 0.2L or more, and even more preferably 0.25L or more.

On the other hand, from the viewpoint of suppressing the occurrence of leakage current, it is preferable that the distances E1 and E2 are each 0.65L or less, more preferably 0.525L or less, and even more preferably 0.4L or less.

From the viewpoint of suppressing bending displacement of the all-solid-state battery 100, it is preferable that the first external electrode 40a and the second external electrode 40b are formed thick. In this embodiment, the thickness of the first external electrode 40a and the second external electrode 40b is preferably 10 μm or more, more preferably 20 μm or more, and even more preferably 50 μm or more.

The thickness of the first external electrode 40a and the second external electrode 40b can be measured as an average of the thicknesses at nine different points. For example, as illustrated in FIG. 7, the thickness of the second external electrode 40b can be measured at nine points: the end (1), corner (3), the midpoint (2) between the end (1) and the corner (3) on the upper surface of the laminated chip 70, the end (9), corner (7), the midpoint (8) between the end (9) and the corner (7) on the lower surface of the laminated chip 70, and three equally spaced points (4) to (6) between the corner (3) and the corner (7). The thickness of the first external electrode 40a can be measured in a similar manner.

On the other hand, if the first external electrode 40a and the second external electrode 40b are too thick, there is a risk of a decrease in capacity density. Therefore, it is preferable to set an upper limit on the thickness of the first external electrode 40a and the second external electrode 40b. In this embodiment, the thickness of the first external electrode 40a and the second external electrode 40b is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less.

The main components of the first external electrode 40a and the second external electrode 40b are, for example, Ag (silver), Cu (copper), Ni (nickel), Pd (palladium), C (carbon), Al (aluminum), Au (gold), etc.

Next, a method for manufacturing the all-solid-state battery 100 illustrated in FIG. 2 will be described. FIG. 8 is a diagram illustrating the flow of the method for manufacturing the all-solid-state battery 100.

(Process for preparing raw material powder for solid electrolyte layer)
First, a raw material powder for the solid electrolyte layer constituting the above-mentioned solid electrolyte layer 30 is prepared. For example, raw materials, additives, etc. are mixed, and a solid-phase synthesis method or the like is used to prepare raw material powder for an oxide-based solid electrolyte. The obtained raw material powder can be dry-milled to adjust to a desired average particle size. For example, the desired average particle size is adjusted using a planetary ball mill using 5 mmφ _ZrO2 balls.

(Cover layer raw material powder preparation process)
First, a ceramic raw material powder is prepared to form the above-described cover layer 50. For example, raw materials, additives, etc. are mixed, and the raw material powder for the cover layer can be prepared by using a solid phase synthesis method or the like.

(Electrode layer paste preparation process)
Next, the internal electrode paste for producing the first internal electrode 10 and the second internal electrode 20 is separately produced. For example, the internal electrode paste can be obtained by uniformly dispersing a conductive assistant, an electrode active material, a solid electrolyte material, a sintering assistant, a binder, a plasticizer, and the like in water or an organic solvent. The above-mentioned solid electrolyte paste may be used as the solid electrolyte material. A carbon material or the like is used as the conductive assistant. A metal may be used as the conductive assistant. Examples of the metal of the conductive assistant include Pd, Ni, Cu, Fe, and alloys containing these. Pd, Ni, Cu, Fe, alloys containing these, and various carbon materials may also be used.

The sintering aid in the internal electrode paste contains one or more glass components, such as Li-B-O compounds, Li-Si-O compounds, Li-C-O compounds, Li-S-O compounds, and Li-P-O compounds.

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

(Solid electrolyte green sheet manufacturing process)
The raw material powder for the solid electrolyte layer is uniformly dispersed in an aqueous or organic solvent together with a binder, a dispersant, a plasticizer, etc., and wet-pulverized to obtain a solid electrolyte slurry having a desired average particle size. At this time, a bead mill, a wet jet mill, various kneaders, a high-pressure homogenizer, etc. can be used, and it is preferable to use a bead mill from the viewpoint of simultaneously adjusting the particle size distribution and dispersing. A binder is added to the obtained solid electrolyte slurry to obtain a solid electrolyte paste. The obtained solid electrolyte paste is coated to produce a solid electrolyte green sheet 51. The coating method is not particularly limited, and a slot die method, a reverse coat method, a gravure coat method, a bar coat method, a doctor blade method, etc. can be used. The particle size distribution after wet-pulverization can be measured, for example, using a laser diffraction measurement device using a laser diffraction scattering method.

(Lamination process)
As illustrated in FIG. 9(a), the internal electrode paste 52 is printed on one side of the solid electrolyte green sheet 51. In the area on the solid electrolyte green sheet 51 where the internal electrode paste 52 is not printed, a reverse pattern 53 is printed. The reverse pattern 53 can be the same as the solid electrolyte green sheet 51. A plurality of printed solid electrolyte green sheets 51 are alternately shifted and stacked. As illustrated in FIG. 9(b), a laminate is obtained by pressing the cover sheet 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 for the first internal electrode 10 is exposed on one end face of the laminate and the internal electrode paste 52 for the second internal electrode 20 is exposed on the other end face of the laminate. The cover sheet 54 can be formed by applying the raw material powder for the cover layer in the same manner as in the solid electrolyte green sheet preparation process. The cover sheet 54 is formed thicker than the solid electrolyte green sheet 51. It may be made thicker during coating, or it may be made thicker by stacking multiple coated sheets.

Next, the external electrode paste 55 is applied to each of the two end faces by a dipping method or the like and then dried. This results in a molded body for forming the all-solid-state battery 100.

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

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

Example 1
A laminated all-solid-state battery was produced according to the above embodiment. A first internal electrode paste for a first internal electrode layer (positive electrode layer) was applied and formed on a first solid electrolyte green sheet by a screen printing method. A margin layer paste for a first margin layer was printed around the first internal electrode paste on the first solid electrolyte green sheet. A second internal electrode paste for a second internal electrode layer (negative electrode layer) was applied and formed on a second solid electrolyte green sheet by a screen printing method. A margin layer paste for a second margin layer was printed around the second internal electrode paste on the second solid electrolyte green sheet. The first internal electrode paste for a positive electrode layer and the second internal electrode paste for a negative electrode layer were made to have the same thickness. A plurality of first solid electrolyte green sheets and a plurality of second solid electrolyte green sheets were laminated so that the positive electrode layer and the negative electrode layer were alternately drawn out to the left and right. The green chip of a laminated all-solid-state battery was obtained by cutting to a predetermined size. The green chip was degreased and fired to sinter it, and a paste for external electrodes was applied and hardened to form a first external electrode and a second external electrode, thereby obtaining a stacked solid-state battery. Ag (silver) was used as the first external electrode, and Cu (copper) was used as the material for the second external electrode. The thickness of the first external electrode was 30 μm, and the thickness of the second external electrode was 50 μm.

The distance E1 at the first external electrode was 0.3L. The distance E2 at the second external electrode was 0.3L. The distance E = E1 + E2 was 0.6L.

Example 2
In Example 2, the distance E1 in the first external electrode was set to 0.4 L. The distance E2 in the second external electrode was set to 0.2 L. The distance E = E1 + E2 was 0.6 L. The other conditions were the same as those in Example 1.

Example 3
In Example 3, the distance E1 in the first external electrode was set to 0.15 L. The distance E2 in the second external electrode was set to 0.35 L. The distance E = E1 + E2 was 0.5 L. The other conditions were the same as those in Example 1.

Example 4
In Example 4, the distance E1 in the first external electrode was set to 0.25 L. The distance E2 in the second external electrode was set to 0.25 L. The distance E = E1 + E2 was 0.5 L. The other conditions were the same as those in Example 1.

Example 5
In Example 5, the distance E1 in the first external electrode was set to 0.15 L. The distance E2 in the second external electrode was set to 0.65 L. The distance E = E1 + E2 was 0.8 L. The other conditions were the same as those in Example 1.

Example 6
In Example 6, the distance E1 in the first external electrode was set to 0.4 L. The distance E2 in the second external electrode was set to 0.4 L. The distance E = E1 + E2 was 0.8 L. The other conditions were the same as those in Example 1.

(Comparative Example 1)
In Comparative Example 1, the distance E1 in the first external electrode was set to 0.1 L. The distance E2 in the second external electrode was set to 0.1 L. The distance E = E1 + E2 was 0.2 L. The other conditions were the same as those in Example 1.

(Comparative Example 2)
In the comparative example 2, the distance E1 in the first external electrode was set to 0.45 L. The distance E2 in the second external electrode was set to 0.45 L. The distance E = E1 + E2 was 0.9 L. The other conditions were the same as those in the example 1.

(Cycle characteristic test)
A cycle characteristic test was performed on each of the all-solid-state batteries of Examples 1 to 6 and Comparative Examples 1 and 2. In the cycle characteristic test, a charge/discharge cycle test was performed at 0.2 C in an environment of 25° C. with an upper limit voltage of 3.3 V and a lower limit voltage of 2.0 V.

As a result of the cycle characteristic test, if the discharge capacity retention rate after 2000 cycles relative to the 1st cycle was 85% or more and 100% or less, it was judged as passing (◯); if it was 60% or more and less than 85%, it was judged as somewhat good (△); and if it was less than 60%, it was judged as failing (×). In Examples 1 to 6 and Comparative Example 1, the cycle characteristic test was judged as passing (◯). This is thought to be because the condition E≦0.8L was satisfied and the leakage current was suppressed.

(Bending test of printed circuit board)
A bending test of a printed circuit board was conducted for each of the all-solid-state batteries of Examples 1 to 6 and Comparative Examples 1 and 2. In the bending test of a printed circuit board, a test board on which an element was mounted was placed in a bending tester and gradually bent at a speed of 1.0 mm/s ±0.5 mm/s until the bending depth reached 1 mm, 2 mm, 3 mm, and 4 mm. The test board was held in the bent state for 20 seconds ±1 second. The aforementioned cycle test was conducted on the elements after the bending test, and the retention rate of the discharge capacity was evaluated.

As a result of the printed circuit board bending test, if the discharge capacity retention rate after 2000 cycles was 85% or more and 100% or less compared to the 1st cycle, it was judged as passing (◯); if it was 60% or more and less than 85%, it was judged as somewhat good (△); and if it was less than 60%, it was judged as failing (×). In Examples 1 to 6 and Comparative Example 2, the printed circuit board bending test was judged as passing (◯). This is thought to be because the condition 0.5L≦E was satisfied and bending was suppressed.

If neither the cycle characteristic test nor the bending property test for a printed circuit board was judged to be a failure, the overall evaluation was judged to be a pass "O". If either the cycle characteristic test or the bending property test for a printed circuit board was judged to be a failure, the overall evaluation was judged to be a failure "X". In Examples 1 to 6, the overall evaluation was judged to be a pass "O". This is thought to be because the condition 0.5L≦E≦0.8L was satisfied. On the other hand, in Comparative Examples 1 and 2, the overall evaluation was judged to be a failure "X". This is thought to be because the condition 0.5L≦E≦0.8L was not satisfied.

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

REFERENCE SIGNS LIST 10 First internal electrode 20 Second internal electrode 30 Solid electrolyte layer 40a First external electrode 40b Second external electrode 50 Cover layer 51 Solid electrolyte green sheet 52 Internal electrode paste 53 Reverse pattern 54 Cover sheet 55 External electrode paste 70 Laminated chip 100 All-solid-state battery

Claims (4)

An all-solid-state battery having a length L,
a laminated chip having a substantially rectangular parallelepiped shape in which solid electrolyte layers and internal electrodes containing an electrode active material are alternately laminated, the laminated chip being formed so that a plurality of the laminated internal electrodes are alternately exposed on two opposing end surfaces;
a first external electrode and a second external electrode provided on the two end surfaces,
When the distances over which the first external electrode and the second external electrode extend in the direction of the length L are distances E1 and E2, respectively, the relationship 0.5L≦(E1+E2)≦0.8L is satisfied. The all-solid-state battery according to claim 1, characterized in that distance E1 and distance E2 are each 0.15 L or more and 0.65 L or less. The all-solid-state battery according to claim 1 or 2, characterized in that the thickness of the first external electrode and the second external electrode is 10 μm or more and 200 μm or less. 3. The all-solid-state battery according to claim 1, wherein a main component of the first external electrode and the second external electrode is Ag (silver), Cu (copper), Ni (nickel), Pd (palladium), C (carbon), Al (aluminum), or Au (gold).

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