Solid-state battery and production method thereof

Abstract

The present disclosure improves the reliability of a solid-state battery using a ceramic package. A solid-state battery (100) according to the present disclosure comprises a ceramic package (10) and a battery element (40). The battery element (40) is arranged in a cavity of the ceramic package (10). The ceramic package (10) is provided with a first bottom surface terminal (22), a second bottom surface terminal, a first side surface terminal (24), and a second side surface terminal. A first electrode layer (41) of the battery element (40) is in contact with the first bottom surface terminal (22) and the first side surface terminal (24), and a second electrode layer of the battery element (40) is in contact with the second bottom surface terminal and the second side surface terminal.

Description

Solid-state battery and method for manufacturing the same

[0001] The present disclosure relates to a solid-state battery and a method for manufacturing the same.

[0002] As a container for a solid-state battery, use of a ceramic package has been considered. Advantages of using a ceramic package include, for example, high airtightness inside the ceramic package, the ability to surface-mount a solid-state battery on a circuit board together with electronic components, and the ability to impart high heat resistance to the solid-state battery.

[0003] Patent Document 1 describes an all-solid-state battery provided with an elastic conductive member disposed between an electrode laminate and the inner bottom surface of a sealing body. The elastic conductive member is in conduction with the conductive path of a concave container. The electrode laminate is pressed toward the inner bottom surface of the concave container by the elastic conductive member.

[0004] Patent Document 2 describes that a positive electrode layer and a negative electrode layer are laminated in a direction in which the base portion of a case body extends. The solid-state battery of Patent Document 2 includes an insulating layer disposed between a battery laminate and a lid portion. Patent Document 2 further describes that bump layers formed of solder may be provided between the positive electrode layer and a positive electrode connection portion and between the negative electrode layer and a negative electrode connection portion, respectively.

[0005] International Publication No. 2024 / 018982 International Publication No. 2012 / 081366

[0006] In view of the reliability of a solid-state battery using a ceramic package, there is room for improvement with respect to the above prior art.

[0007] This disclosure comprises a ceramic package having a cavity formed therein having two pairs of sides parallel to each other when viewed from a first surface in plan view, and a battery element disposed within the cavity and having two pairs of sides parallel to each other when viewed from a plan view, wherein the battery element includes a first electrode layer, a solid electrolyte layer, and a second electrode layer, and the width direction is defined as the direction perpendicular to the stacking direction of the first electrode layer, the solid electrolyte layer, and the second electrode layer and the depth direction of the cavity, the stacking direction and the depth direction are perpendicular to each other, and the cavity includes an opening formed on the first surface, an internal bottom surface located opposite to the opening in the depth direction, a pair of first internal sides facing each other in the width direction, and a pair of second internal sides facing each other in the stacking direction. The ceramic package provides a solid-state battery comprising: a first bottom terminal provided on the inner bottom surface; a second bottom terminal provided on the inner bottom surface so as to be insulated from the first bottom terminal; a first side terminal provided on at least one of the pair of first inner sides and electrically connected to the first bottom terminal; and a second side terminal provided on at least one of the pair of first inner sides and electrically connected to the second bottom terminal, wherein the first electrode layer is in contact with the first bottom terminal and the first side terminal, and the second electrode layer is in contact with the second bottom terminal and the second side terminal.

[0008] The technology described herein can improve the reliability of solid-state batteries using ceramic packages.

[0009] Figure 1 is a cross-sectional view of the solid-state battery according to Embodiment 1 along line II. Figure 2 is a plan view of the solid-state battery with the cover removed. Figure 3 is a perspective view of the package body. Figure 4 is a perspective view of the battery element. Figure 5 is a manufacturing process diagram of the solid-state battery. Figure 6 is a cross-sectional view of the solid-state battery according to Embodiment 2 along line VI-VI. Figure 7 is a plan view of the solid-state battery with the cover removed. Figure 8 is a perspective view of the package body. Figure 9 shows other shapes of the protrusions.

[0010] (Knowledge forming the basis of this disclosure) One of the technical challenges when using ceramic packages as containers for solid-state batteries is to improve the reliability of the electrical connection between the ceramic package and the electrodes of the solid-state battery.

[0011] Solid-state batteries using ceramic packages are surface-mounted onto a circuit board via a solder reflow process along with electronic components. Considering the solder reflow process during surface mounting, it is technically difficult to provide bump layers between the positive electrode layer and the positive electrode connection, and between the negative electrode layer and the negative electrode connection, as in the solid-state battery described in Patent Document 2.

[0012] When considering surface mounting solid-state batteries using ceramic packages onto circuit boards, miniaturization of the solid-state battery is required. However, additional components such as the elastic conductive member described in Patent Document 1 hinder the miniaturization of solid-state batteries. For example, the ceramic package requires both the elastic conductive member and a special structure for fixing the elastic conductive member, which hinders the miniaturization and cost reduction of the solid-state battery. Furthermore, the electrode stack, which is the power generation component of the solid-state battery, tends to have large dimensional variations in the thickness direction, which is the stacking direction. Therefore, high dimensional accuracy and high assembly accuracy are required for the elastic conductive member in order to apply sufficient pressing force to the electrode stack. This increases the difficulty of manufacturing solid-state batteries and causes a decrease in yield during manufacturing.

[0013] In view of the above circumstances, this disclosure provides a technology for improving the reliability of electrical connections between a ceramic package and a battery element through a simple structure and simple manufacturing method.

[0014] In another aspect, this disclosure provides a technique for fixing a battery element inside a ceramic package using a simple structure and a simple manufacturing method.

[0015] The embodiments of this disclosure will be described below with reference to the drawings. This disclosure is not limited to the embodiments described below.

[0016] (Embodiment 1) Figure 1 is a cross-sectional view of a solid-state battery 100 according to Embodiment 1 along line II. The solid-state battery 100 comprises a ceramic package 10 and a battery element 40. The ceramic package 10 comprises a cavity CA. The battery element 40 is arranged in the cavity CA. The solid-state battery 100 can be surface-mounted to a circuit board by soldering.

[0017] The ceramic package 10 includes a package body 20 and a lid 30. The package body 20 is the portion in which the cavity CA is formed. The lid 30 is bonded to the package body 20 to seal the cavity CA.

[0018] Figure 2 is a plan view of the solid battery 100 with the cover 30 removed. Figure 3 is a perspective view of the package body 20. Figure 4 is a perspective view of the battery element 40.

[0019] As shown in Figure 2, the package body 20 has two pairs of sides that are parallel to each other when viewed from the first surface. The first surface is the top surface of the package body 20. The cavity CA also has two pairs of sides that are parallel to each other when viewed from the top. The battery element 40 also has two pairs of sides that are parallel to each other when viewed from the top. In each of the package body 20, cavity CA, and battery element 40, one pair of sides is perpendicular to the other pair of sides.

[0020] For example, if a ceramic package has two pairs of parallel sides when viewed from above, and a circular cavity is provided in that cavity, and a circular battery element is placed in that cavity, the ratio of the area of ​​the battery element to the area of ​​the ceramic package is small. In other words, the volumetric efficiency and energy density of the solid-state battery are low.

[0021] In contrast, according to this embodiment, a cavity CA having two pairs of parallel sides is provided in a package body 20 having two pairs of parallel sides, and a battery element 40 having two pairs of parallel sides is arranged in the cavity CA. With this configuration, the ratio of the area of ​​the battery element 40 to the area of ​​the ceramic package 10 is large. In other words, according to this embodiment, the volumetric efficiency and energy density of the solid battery 100 can be improved.

[0022] In this disclosure, the shape having two pairs of parallel sides when viewed from above with respect to the outside of the package body 20, the cavity CA side, and the battery element 40 includes both cases where a radius or chamfer is provided at the corner where two adjacent sides of the shape connect, and cases where the corners intersect.

[0023] As shown in Figures 2 and 3, the cavity CA includes an internal bottom surface 20b, a pair of opposing first internal sides 20p, and a pair of opposing second internal sides 20q. The cavity CA includes an opening formed on the first surface (top surface) of the package body 20. In the depth direction of the cavity CA, the internal bottom surface 20b is located on the opposite side of the opening. The ceramic package 10 includes a first bottom terminal 22, a second bottom terminal 23, a pair of first side terminals 24, and a pair of second side terminals 25. The first bottom terminals 22 and the second bottom terminals 23 are terminals provided on the internal bottom surface 20b. Each of the first bottom terminals 22 and the second bottom terminals 23 constitutes a part of the internal bottom surface 20b. Each of the first side terminals 24 and the second side terminals 25 constitutes a part of the first internal side surface 20p. The second bottom terminals 23 are insulated from the first bottom terminals 22. The first side terminals 24 are provided on each of the pair of first internal side surfaces 20p and are electrically connected to the first bottom terminals 22. The second side terminals 25 are provided on each of the pair of first internal side surfaces 20p and are electrically connected to the second bottom terminals 23.

[0024] As shown in Figure 1, the package body 20 includes a via conductor 28 and a first external terminal 29. The first external terminal 29 is provided on the outer bottom surface of the package body 20. The via conductor 28 penetrates the bottom of the package body 20 and extends from the inner bottom surface 20b to the outer bottom surface of the package body 20. The via conductor 28 connects the first bottom terminal 22 and the first external terminal 29. The first external terminal 29 is connected to the circuit board via solder.

[0025] Although not shown in Figure 1, a similar structure is also provided on the side of the second bottom terminal 23. That is, the package body 20 includes a via conductor and a second external terminal. The second external terminal is provided on the external bottom surface of the package body 20. The via conductor penetrates the bottom of the package body 20 and extends from the internal bottom surface 20b to the external bottom surface of the package body 20. The second bottom terminal 23 and the second external terminal are connected by the via conductor. The second external terminal is connected to the circuit board via solder.

[0026] The package body 20 is made of a ceramic material such as alumina ceramic or aluminum nitride ceramic. The first bottom terminal 22, the second bottom terminal 23, the pair of first side terminals 24, the pair of second side terminals 25, the via conductor 28, and the external terminals (first external terminal and second external terminal) are made of a metallic material such as W, Mo, Cu, Ag, Cu alloy, or Ag alloy. The surfaces of the first bottom terminal 22, the second bottom terminal 23, the pair of first side terminals 24, the pair of second side terminals 25, and the external terminals (first external terminal and second external terminal) are plated with Ni and Au. The lid 30 is made of a metallic material with a low coefficient of thermal expansion, such as Kovar. The lid 30 may also be made of an insulating material such as ceramic.

[0027] As shown in Figures 2 and 4, the battery element 40 includes a first electrode layer 41, a solid electrolyte layer 43, and a second electrode layer 42. The first electrode layer 41 is, for example, a positive electrode layer. The second electrode layer 42 is, for example, a negative electrode layer. The direction perpendicular to the stacking direction SD of the first electrode layer 41, the solid electrolyte layer 43, and the second electrode layer 42 is defined as the width direction FD. The stacking direction SD and the width direction FD are perpendicular to the depth direction of the cavity CA. A pair of first internal sides 20p are located in the width direction FD. The orientation of the battery element 40 in the cavity CA is determined such that the first electrode layer 41 is in contact with the first bottom terminal 22 and the first side terminal 24, and the second electrode layer 42 is in contact with the second bottom terminal 23 and the second side terminal 25. The battery element 40 is constrained by the ceramic package 10 in the width direction FD. In other words, the first electrode layer 41 of the battery element 40 is pressed against a pair of first side terminals 24. The second electrode layer 42 of the battery element 40 is pressed against a pair of second side terminals 25. The solid electrolyte layer 43 of the battery element 40 is pressed against a pair of first internal side surfaces 20p. This fixes the battery element 40 to the ceramic package 10. The solid battery 100 can be manufactured by placing the battery element 40 in a cavity CA and then expanding the battery element 40.

[0028] In the solid-state battery 100 of this embodiment, the battery element 40 is fixed to the ceramic package 10 by a restraining force from the ceramic package 10. Therefore, in the solid-state battery 100 of this embodiment, other members such as elastic conductive members for pressing can be omitted, and soldering between the battery element 40 and the ceramic package 10 can also be omitted. This is advantageous for miniaturizing the solid-state battery 100, reducing costs, and improving volumetric energy density. According to this embodiment, the battery element 40 can be fixed inside the ceramic package 10 with a simple structure. In addition, not only the first bottom terminal 22 and the second bottom terminal 23, but also the first side terminal 24 and the second side terminal 25 are in contact with the battery element 40. This improves the reliability of the electrical connection between the ceramic package 10 and the battery element 40. As a result, the electrical characteristics of the solid-state battery 100, such as rate characteristics, are improved or stabilized.

[0029] The battery element 40 is in contact with the first bottom terminal 22 and the second bottom terminal 23 in such a way that it is pressed against them. In other words, on both the side and bottom surfaces of the ceramic package 10, the battery element 40 is in contact with the internal terminals of the ceramic package 10.

[0030] The stacking direction SD and width direction FD of the first electrode layer 41, the solid electrolyte layer 43, and the second electrode layer 42 are perpendicular to the depth direction of the cavity CA.

[0031] As shown in Figure 3, the first bottom terminal 22 and the second bottom terminal 23 each have a short side and a long side when viewed from the first surface in a plan view. On the internal bottom surface 20b, the first bottom terminal 22 and the second bottom terminal 23 are arranged parallel to each other. The length of the long side of the first bottom terminal 22 and the length of the long side of the second bottom terminal 23 are equal to, for example, the distance between the first internal surface 20p and the first internal surface 20p. The length of the short side of the first bottom terminal 22 may be equal to, shorter than, or longer than the dimension (thickness) of the first electrode layer 41 in the stacking direction SD. Preferably, the length of the short side of the first bottom terminal 22 is equal to or longer than the dimension (thickness) of the first electrode layer 41 in the stacking direction SD. Even if the length of the shorter side of the first bottom terminal 22 is longer than the dimensions of the first electrode layer 41 in the stacking direction SD, the first bottom terminal 22 does not fundamentally overlap with the solid electrolyte layer 43, but it may overlap. The length of the shorter side of the second bottom terminal 23 may be equal to the dimensions (thickness) of the second electrode layer 42 in the stacking direction SD, shorter than it, or longer than it. It is desirable that the length of the shorter side of the second bottom terminal 23 is equal to or longer than the dimensions (thickness) of the second electrode layer 42 in the stacking direction SD. Even if the length of the shorter side of the second bottom terminal 23 is longer than the dimensions of the second electrode layer 42 in the stacking direction SD, the second bottom terminal 23 does not fundamentally overlap with the solid electrolyte layer 43, but it may overlap. The shape and dimensions of the second bottom terminal 23 may be equal to the shape and dimensions of the first bottom terminal 22.

[0032] The first bottom terminal 22 and the second bottom terminal 23 may each have no short side and long side when viewed from the first surface, and their side lengths may be the same. The side lengths of the first bottom terminal 22 and the second bottom terminal 23 in the width direction FD are, for example, equal to the distance between the first internal surface 20p and the first internal surface 20p. The side length of the first bottom terminal 22 in the stacking direction SD may be equal to, shorter than, or longer than the dimension (thickness) of the first electrode layer 41 in the stacking direction SD. It is desirable that the side length of the first bottom terminal 22 in the stacking direction SD be equal to or longer than the dimension (thickness) of the first electrode layer 41 in the stacking direction SD. Even when the side length of the first bottom terminal 22 in the stacking direction SD is longer than the dimension of the first electrode layer 41 in the stacking direction SD, the first bottom terminal 22 does not basically overlap with the solid electrolyte layer 43, but it may overlap. The length of the side of the second bottom terminal 23 in the stacking direction SD is preferably equal to or longer than the dimension (thickness) of the second electrode layer 42 in the stacking direction SD. Even if the length of the side of the second bottom terminal 23 in the stacking direction SD is longer than the dimension of the second electrode layer 42 in the stacking direction SD, the second bottom terminal 23 does not fundamentally overlap with the solid electrolyte layer 43, but it may overlap. The shape and dimensions of the second bottom terminal 23 may be equal to the shape and dimensions of the first bottom terminal 22.

[0033] As shown in Figure 3, the first side terminal 24 extends in the depth direction of the cavity CA and is in contact with the short side of the stacking direction SD of the first bottom terminal 22. The second side terminal 25 extends in the depth direction of the cavity CA and is in contact with the short side of the stacking direction SD of the second bottom terminal 23. The shape of the first side terminal 24 may be the same as or different from the shape of the second side terminal 25. The dimensions of the first side terminal 24 may be equal to or different from the dimensions of the second side terminal 25. The depth dimensions of the first side terminal 24 and the second side terminal 25 may be equal to, lower than, or higher than the dimensions (height) of the paired first electrode layer 41 and second electrode layer 42, respectively. The depth dimensions of the first side terminal 24 and the second side terminal 25 may be equal to, or preferably higher than, the dimensions (height) of the paired first electrode layer 41 and second electrode layer 42, respectively.

[0034] In this embodiment, the first side terminal 24 is provided on each of the pair of first internal side surfaces 20p. The second side terminal 25 is provided on each of the pair of first internal side surfaces 20p. With this configuration, the reliability of the electrical connection between the ceramic package 10 and the battery element 40 can be further improved. However, the first side terminal 24 may be provided on only one of the pair of first internal side surfaces 20p. The second side terminal 25 may be provided on only one of the pair of first internal side surfaces 20p.

[0035] As shown in Figure 2, the pair of second internal surfaces 20q are positioned in a direction parallel to the stacking direction SD of the battery element 40. In the direction parallel to the stacking direction SD, a gap 34 exists between at least one of the pair of second internal surfaces 20q and the battery element 40. In this embodiment, a gap 34 exists between each of the pair of second internal surfaces 20q and the battery element 40.

[0036] As shown in Figure 4, the battery element 40 has a rectangular parallelepiped shape. Three layers, a first electrode layer 41, a solid electrolyte layer 43, and a second electrode layer 42, are stacked along the stacking direction SD. The dimensional accuracy of the battery element 40 in the width direction FD, which is perpendicular to the stacking direction SD, is higher than the dimensional accuracy of the battery element 40 in the stacking direction SD. This is because the dimensions of the battery element 40 in the width direction FD are controlled with high precision by the dimensions of the molding die. On the other hand, the dimensions of the battery element 40 in the stacking direction SD reflect the thickness variation due to the mass variation of the battery element 40. Therefore, the dimensional variation of the battery element 40 in the stacking direction SD is large. The orientation of the battery element 40 in the cavity CA is determined so that both end faces of the battery element 40 in the width direction FD are in contact with the ceramic package 10. Therefore, the restraining force from the ceramic package 10 can be reliably applied to the battery element 40. Furthermore, since a gap 34 is provided between each of the end faces of the battery element 40 in the stacking direction SD and at least one of the pair of second internal side surfaces 20q, dimensional variations of the battery element 40 in the stacking direction SD can be absorbed by the gap 34.

[0037] In Figure 4, the first electrode layer 41, solid electrolyte layer 43, and second electrode layer 42 of the battery element 40 have the same dimensions (width) in the width direction FD. However, at least one selected from the first electrode layer 41 and the second electrode layer 42 may be larger than the solid electrolyte layer 43 in the width direction FD. With this configuration, it is easier to apply a restraining force from the ceramic package 10 using at least one selected from the first electrode layer 41 and the second electrode layer 42.

[0038] Each of the first electrode layer 41 and the second electrode layer 42 may have a pair of parallel short sides and a pair of parallel long sides when viewed from above in the depth direction of the cavity CA, or the pair of parallel sides and the pair of parallel sides may be of the same length. When there are short sides and long sides, it is desirable that the stacking direction SD is parallel to the short side and the width direction FD is parallel to the long side. In the width direction FD parallel to the long side, at least one selected from the first electrode layer 41, the second electrode layer 42, and the solid electrolyte 43 may be constrained by the ceramic package 10. This is because the change in dimensions when the battery element 40 is expanded is greatest in the width direction FD. Also, in the case of sides of the same length without short sides and long sides, at least one selected from the first electrode layer 41, the second electrode layer 42, and the solid electrolyte 43 may be constrained by the ceramic package 10 in the width direction FD.

[0039] In the battery element 40, if the first electrode layer 41 is the positive electrode layer, the first electrode layer 41 includes materials such as a positive electrode active material, a conductive material, and a solid electrolyte. The first electrode layer 41 may also include a binder. If the second electrode layer 42 is the negative electrode layer, the second electrode layer 42 includes materials such as a negative electrode active material, a conductive material, and a solid electrolyte. The second electrode layer 42 may also include a binder.

[0040] The positive electrode active material may be a material that has the ability to intercept and release metal ions such as lithium ions. Examples of positive electrode active materials include lithium-containing transition metal oxides, lithium-containing transition metal phosphates, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal oxysulfides, and transition metal oxynitrides. Examples of lithium-containing transition metal oxides include lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, and lithium nickel manganese oxide. Examples of lithium-containing transition metal phosphates include lithium iron phosphate, lithium vanadium phosphate, lithium cobalt phosphate, and lithium nickel phosphate.

[0041] The negative electrode active material may be a material that has the ability to intercept and release metal ions such as lithium ions. Examples of negative electrode active materials include carbon materials, materials capable of forming alloys with metal ions, and oxide-based materials. An example of a carbon material is graphite. Examples of materials capable of forming alloys with lithium include silicon, silicon-containing oxides, tin, zinc alloys, bismuth, germanium, aluminum, and other materials capable of forming alloys with lithium. Examples of oxide-based materials include titanium oxide, lithium titanium oxide, niobium oxide, titanium niobium oxide, silicon-containing oxides, tin-containing oxides, iron oxides, zinc oxides, molybdenum oxide, vanadium oxide, and lithium-containing vanadium oxide. One of these negative electrode active materials may be used, or two or more may be used in combination.

[0042] Examples of conductive materials include carbon materials, conductive polymer compounds, and metals. Examples of carbon materials include carbon black, graphite, acetylene black, carbon nanotubes, carbon nanofibers, graphene, fullerenes, and graphite oxide. Examples of conductive polymer compounds include polyaniline, polypyrrole, and polythiophene. Examples of metals include aluminum and nickel.

[0043] Examples of the binder include polymer materials such as polyvinylidene fluoride, vinylidene fluoride - hexafluoropropylene copolymer, vinylidene fluoride - tetrafluoroethylene copolymer, polytetrafluoroethylene, carboxymethyl cellulose, polyacrylic acid, styrene - butadiene copolymer rubber, polypropylene, polyethylene, and polyimide. Examples of the binder also include inorganic materials such as silicate - based, phosphate - based, and cement - based materials.

[0044] Examples of the solid electrolyte include halide solid electrolyte, sulfide solid electrolyte, oxide solid electrolyte, polymer solid electrolyte, complex hydride solid electrolyte, and the like.

[0045] The solid electrolyte layer 43 is disposed between the first electrode layer 41 and the second electrode layer 42. Examples of the solid electrolyte contained in the solid electrolyte layer 43 include halide solid electrolyte, sulfide solid electrolyte, oxide solid electrolyte, polymer solid electrolyte, complex hydride solid electrolyte, and the like. One kind selected from these solid electrolytes may be used, or two or more kinds may be used in combination. The solid electrolyte contained in the first electrode layer 41 may have the same composition as the solid electrolyte contained in the solid electrolyte layer 43, or may have a different composition. The solid electrolyte contained in the second electrode layer 42 may have the same composition as the solid electrolyte contained in the solid electrolyte layer 43, or may have a different composition. The solid electrolyte contained in the first electrode layer 41 may have the same composition as the solid electrolyte contained in the second electrode layer 42, or may have a different composition. The first electrode layer 41 may contain two or more kinds of solid electrolytes. The second electrode layer 42 may contain two or more kinds of solid electrolytes. Further, instead of only the solid electrolyte, an electrolyte mixture containing the solid electrolyte and a binder used for the electrode layer may be used for the solid electrolyte layer 43.

[0046] In this embodiment, the battery element 40 does not have a metal current collector. The first electrode layer 41 can be the molded body of the positive electrode mixture itself. The second electrode layer 42 can be the molded body of the negative electrode mixture itself. The solid electrolyte layer 43 can be the molded body of the solid electrolyte or the electrolyte mixture itself. When the solid electrolyte layer 43 has a thin film shape, the solid electrolyte layer 43 may be formed by a coating process. In the solid battery 100, the first electrode layer 41 is directly in contact with the first bottom terminal 22 and the first side terminal 24. The second electrode layer 42 is directly in contact with the second bottom terminal 23 and the second side terminal 25. According to such a configuration, when the battery element 40 is disposed in the cavity CA and expanded, the reliability of the electrical connection between the battery element 40 and the ceramic package 10 can be enhanced. However, the first electrode layer 41 may have a metal current collector, and the second electrode layer 42 may have a metal current collector.

[0047] As shown in FIG. 1, only the space 32 exists between the battery element 40 and the lid body 30. In the depth direction of the cavity CA, no load is applied to the battery element 40. According to such a configuration, neither the elastic conductive material member for pressing nor the special structure for fixing the member is required for the ceramic package 10. This advantageously contributes to the miniaturization, cost reduction, and improvement of the volume energy density of the solid battery 100. Further, not only the clearance 34 but also the space 32 can absorb the volume expansion accompanying the charge and discharge of the battery element 40. Also, an insulating sheet may be provided on the surface of the battery element 40 between the lid body 30 and the battery element 40 while maintaining the space 32. According to such a configuration, the occurrence of an internal short circuit due to the movement of foreign matters such as fine powder and metal powder through the space 32 can be prevented.

[0048] Note that the solid battery of the present disclosure may further include an elastic conductive member for pressing or an elastic conductive member for pressing and a special structure for fixing the member to the ceramic package. By providing the pressing member, the vertical pressing in the depth direction of the cavity CA is also applied to the battery element 40, and the electrical characteristics of the solid battery become more stable.

[0049] Next, a method for manufacturing the solid battery 100 will be described.

[0050] Figure 5 is a diagram illustrating the manufacturing process of a solid-state battery 100. In step S1, the battery element 40 is manufactured. In step S2, the ceramic package 10 is manufactured. Specifically, the package body 20 and the lid 30 are manufactured. The order of steps S1 and S2 is not limited.

[0051] The battery element 40 is manufactured such that its dimensions in the width direction FD are shorter than the distance between the first internal side surfaces 20p, the distance between the first side terminals 24, and the distance between the second side terminals 25. With this configuration, the battery element 40 can be smoothly inserted into the cavity CA. In order to ensure a gap 34, the dimensions of the battery element 40 in the stacking direction SD are shorter than the distance between the second internal side surfaces 20q.

[0052] The package body 20 can be manufactured by known methods. Specifically, multiple ceramic green sheets are laminated to form a laminate, and the internal via wiring is created. After firing the laminate, nickel plating is applied to the terminal portions of the fired product. A brazing material for joining the lid 30 to the package body 20 is placed on the open end face of the fired product. Then, Au plating is applied over the nickel plating. Each side electrode inside the package body 20 can be manufactured in the same way as the external electrodes and bottom electrodes. Alternatively, other conventional methods for manufacturing shellac packages may be used.

[0053] After fabricating the battery element 40 and the ceramic package 10, as shown in step S3 in Figure 5, the battery element 40 is placed in the cavity CA such that the first electrode layer 41 is in contact with the first bottom terminal 22 and the second electrode layer 42 is in contact with the second bottom terminal 23.

[0054] As shown in step S4, the battery element 40 is expanded in the width direction FD such that the first electrode layer 41 and the first side terminal 24 and the second electrode layer 42 and the second side terminal 25 come into contact in the width direction FD, and a restraining force from the ceramic package 10 (specifically the package body 20) acts on the battery element 40. As a result, the battery element 40 is fixed to the package body 20, and the first electrode layer 41 comes into contact with the first bottom terminal 22 and the first side terminal 24, and the second electrode layer 42 comes into contact with the second bottom terminal 23 and the second side terminal 25, thereby ensuring electrical connection. According to the method of this embodiment, the battery element 40 can be fixed to the ceramic package 10 without using means such as an elastic conductive member for pressing or soldering, and the reliability of the electrical connection between the ceramic package 10 and the battery element 40 can be improved.

[0055] Step S4 specifically includes charging the battery element 40. For example, in a solid-state battery, the positive and negative electrodes each expand by a few percent in volume during charging and discharging. Once a solid-state battery expands, it tends not to shrink back to its original dimensions and maintains its expanded dimensions. Therefore, after placing the battery element 40 in the cavity CA, charging the battery element 40 causes it to expand and make close contact with the first internal side surface 20p of the package body 20. Since the first side terminal 24 and the second side terminal 25 are provided, the first electrode layer 41 makes close contact with the first side terminal 24, and the second electrode layer 42 makes close contact with the second side terminal 25. As a result, the battery element 40 makes electrical contact with the first bottom terminal 22, the second bottom terminal 23, the first side terminal 24, and the second side terminal 25, respectively, making it possible to realize a low-resistance solid-state battery 100. Furthermore, this method does not require any special process to fix the battery element 40 to the ceramic package 10. To improve the adhesion between the battery element 40 and the first side terminal 24, it is desirable that the initial gap between the battery element 40 and the first side terminal 24 before the battery element 40 expands is smaller than the amount of expansion of the first electrode layer 41. Similarly, to improve the adhesion between the battery element 40 and the second side terminal 25, it is desirable that the initial gap between the battery element 40 and the second side terminal 25 before the battery element 40 expands is smaller than the amount of expansion of the second electrode layer 42. With such a configuration, the resistance of the solid battery 100 can be stabilized.

[0056] Alternatively, the battery element 40 may be expanded by heating. In other words, the thermal expansion properties of the electrode material and solid electrolyte constituting the battery element 40 can be applied. A common indicator is the coefficient of linear expansion. In particular, the expansion amount of the electrode layer, which includes conductive materials with a large coefficient of linear expansion and binders with a large coefficient of linear expansion, tends to be large. The battery element 40 is manufactured by tablet molding a molded body including the electrode layer and the solid electrolyte layer. When the heating of the battery element 40 is finished and the temperature drops, the gaps between particles are difficult to fill. Therefore, once the battery element 40 expands, it is difficult to contract. The solid electrolyte also expands in volume, so heating is more desirable from the viewpoint of constraining the battery element 40 and the ceramic package. A batch furnace, tunnel furnace, etc., can be used to heat the battery element 40. Alternatively, the solder reflow process for mounting the solid battery 100 on a circuit board may be combined with heating. With such a method, no special process is required to fix the battery element 40 to the ceramic package 10. If the heating temperature of the battery element 40 is lower than the reflow temperature in the solder reflow process, the restraining force will increase further after the solder reflow process for mounting the solid battery 100 onto the circuit board.

[0057] To expand the battery element 40, it is more effective to charge the battery element 40 while heating it. For example, the battery element 40 may be charged in a temperature environment of 85°C, 100°C, 125°C, or 150°C. Heating also reduces the resistance of the battery element 40, and the charging time can be significantly shortened compared to room temperature, thus greatly improving work efficiency. In addition, the battery element 40 may be heated after charging, or heated before charging. Furthermore, heating and charging of the battery element 40 may be performed simultaneously. Note that "heating and charging simultaneously" does not necessarily mean that the start and end times of heating coincide with the start and end times of charging, but rather that at least a portion of the heating process overlaps with the charging process.

[0058] Step S4 may be performed before joining the lid 30 to the package body 20, or after joining the lid 30 to the package body 20.

[0059] (Embodiment 2) Figure 6 is a cross-sectional view of the solid battery 200 according to Embodiment 2 along the line VI-VI. Figure 7 is a plan view of the solid battery 200 with the cover 30 removed. Figure 8 is a perspective view of the package body 20S.

[0060] The solid-state battery 200 comprises a ceramic package 10S and a battery element 40. The ceramic package 10S further comprises electrically insulating protrusions 27 provided on each of a pair of first internal sides 20p. The protrusions 27 are located facing the solid electrolyte layer 43 of the battery element 40. That is, the protrusions 27 are located between the first side terminal 24 and the second side terminal 25. The solid electrolyte layer 43 of the battery element 40 is in contact with one or both of the pair of protrusions 27. Except for the protrusions 27, the structure of the ceramic package 10S is the same as that of the ceramic package 10 described in Embodiment 1.

[0061] As explained earlier, the battery element 40 expands due to charging or heating. However, the solid electrolyte layer 43 hardly expands with charging. Therefore, with the ceramic package 10 of Embodiment 1, a small gap may occur between the solid electrolyte layer 43 and the first internal side surface 20p of the ceramic package 10. In contrast, with the ceramic package 10S, the solid electrolyte layer 43 can be supported by the protrusions 27. Combined with the restraining force acting from the ceramic package 10S on the first electrode layer 41 and the second electrode layer 42, the battery element 40 can be fixed inside the ceramic package 10S by the protrusions 27. Furthermore, the protrusions 27 are provided at a position facing the solid electrolyte layer 43. Since the solid electrolyte layer 43 also expands when heating or charging while heating is performed, the effect of fixing the battery element 40 inside the ceramic package 10S by the protrusions 27 is further enhanced. In addition, the protrusions 27 prevent the first electrode layer 41 and the second electrode layer 42 from wrapping around the side surface of the solid electrolyte layer 43 when the battery element 40 expands. Therefore, the projection 27 can prevent internal short circuits between the first electrode layer 41 and the second electrode layer 42 that occur when the battery element 40 expands during charging and discharging.

[0062] One of the challenges associated with charging and discharging solid-state batteries is internal short circuits caused by cracks occurring in the electrode layer or at the interface between the electrode layer and the solid electrolyte layer at the ends of the battery element in the width direction FD. According to this embodiment, by providing the protrusion 27, internal short circuits between the first electrode layer 41 and the second electrode layer 42 can be prevented.

[0063] The ceramic package 10S includes a package body 20S. Except for the protrusions 27, the structure of the package body 20S is the same as that of the package body 20 described in Embodiment 1.

[0064] In this embodiment, the projection 27 is a ceramic portion integrally formed on the package body 20S. With this configuration, no additional steps or additional parts are required to form the projection 27.

[0065] The projection 27 is located within the range where the solid electrolyte layer 43 exists in the stacking direction SD of the battery element 40. The dimensions (width) of the projection 27 in the stacking direction SD may be equal to, smaller than, or larger than the dimensions (thickness) of the solid electrolyte layer 43 in the stacking direction SD. Preferably, the dimensions (width) of the projection 27 in the stacking direction SD are equal to or smaller than the dimensions (thickness) of the solid electrolyte layer 43 in the stacking direction SD. The "projection height" of the projection 27 refers to the projection height from the first internal side surface 20p. The projection height is at least equal to or greater than the first side terminal 24 or the second side terminal 25.

[0066] In this embodiment, the projections 27 are provided on each of the pair of first internal surfaces 20p. With this configuration, both end faces of the solid electrolyte layer 43 can be supported by the projections 27. However, the projections 27 may be in contact with only one of the two end faces of the solid electrolyte layer 43. Also, the projections 27 may be provided on only one of the pair of first internal surfaces 20p.

[0067] As shown in Figure 7, after expansion in step S4 of the manufacturing process, the first electrode layer 41 is in contact with the first side terminal 24, the second electrode layer 42 is in contact with the second side terminal 25, and the solid electrolyte layer 43 is in contact with the projection 27. The dimensions of the width direction FD in Figure 4 may be determined in advance, taking into account the amount of expansion of the electrode layers and solid electrolyte of the battery element 40, and at least one selected from the first electrode layer 41 and the second electrode layer 42 may be larger than the solid electrolyte layer 43 in the width direction FD. If the electrode layer is larger than the solid electrolyte layer 43, an effect such as preventing misalignment of the stacking direction SD of the ceramic package cavity CA during insertion can be expected. In addition, the restraining force from the ceramic package 10S can be easily applied by at least one selected from the first electrode layer 41 and the second electrode layer 42.

[0068] The projection 27 preferably extends from the inner bottom surface 20b to the upper end surface of the package body 20S, but it does not have to extend to the upper end surface. If it does not extend to the upper end surface, it is preferable that the dimension (height) of the projection 27 in the depth direction of the cavity CA is greater than the dimension (height) of the battery element 40. With this configuration, the projection 27 can support the solid electrolyte layer 43, and the effect of preventing internal short circuits between the first electrode layer 41 and the second electrode layer 42 is also enhanced.

[0069] In the examples shown in Figures 7 and 8, the projection 27 has the shape of a rectangular prism. However, the shape of the projection 27 is not particularly limited. Figure 9 shows other shapes of the projection 27.

[0070] As shown in Figure 9(a), the projection 27 may have a triangular prism shape. With the projection 27 shown in Figure 9(a), the tip of the projection 27 is a point. Therefore, compared to a projection 27 with a rectangular prism shape, it becomes easier to insert the battery element 40 into the package body 20S, and the gap between the solid electrolyte layer 43 and the projection 27 can be made smaller. Furthermore, the projection 27 shown in Figure 9(a) is desirable because it can secure space that can accommodate irregular volume changes between the end of the solid electrolyte layer 43 and the end of the first electrode layer 41 or the second electrode layer 42 in the width direction FD.

[0071] As shown in Figure 9(b), the projection 27 may have a semi-cylindrical shape. With the projection 27 shown in Figure 9(b), the tip of the projection 27 becomes a point. Therefore, compared to a projection 27 with a rectangular prism shape, it becomes easier to insert the battery element 40 into the package body 20S, and the gap between the battery element 40 and the projection 27 can be made smaller. Furthermore, the projection 27 shown in Figure 9(b) is desirable because it can accommodate irregular volume changes between the end of the solid electrolyte layer 43 and the end of the first electrode layer 41 or the second electrode layer 42 in the width direction FD with a curved surface.

[0072] As shown in Figure 9(c), the projection 27 may have the shape of a trapezoidal column.

[0073] As shown in Figures 9(d), (e), and (f), the projection 27 may be composed of a plurality of parts 27a aligned in the stacking direction SD. When the projection 27 is composed of a plurality of parts 27a, the projection 27 is provided such that the solid electrolyte layer 43 is in contact with at least one of the parts 27a. When the projection 27 is provided such that some or all of the plurality of parts 27a are in contact with the solid electrolyte layer 43, in addition to fixing the solid electrolyte layer 43, the effect of preventing internal short circuits is further enhanced. When the projection 27 is composed of a plurality of parts 27a, it is not necessary for all of the plurality of parts 27a to have the same dimensions. For example, the projection 27 may be designed such that the central part 27a has the largest projection height. By arranging the part 27a with the largest projection height to be in contact with the solid electrolyte layer 43, the solid electrolyte layer 43 can be fixed more securely, and the effect of preventing internal short circuits is further enhanced. Furthermore, although not shown in the figures, if the projection 27 is composed of multiple parts 27a, the projection 27 may be made up of two or more parts selected from a triangular prism, a semi-cylinder, and a trapezoidal prism.

[0074] (Other Embodiments) (Note) The above description of embodiments discloses the following technologies.

[0075] (Technology 1) A ceramic package having a cavity formed thereon having two pairs of sides parallel to each other when viewed from a first surface in plan view, and a battery element disposed within the cavity and having two pairs of sides parallel to each other when viewed from a plan view, wherein the battery element includes a first electrode layer, a solid electrolyte layer, and a second electrode layer, and when the direction perpendicular to the stacking direction of the first electrode layer, the solid electrolyte layer, and the second electrode layer and the depth direction of the cavity are defined as the width direction, the stacking direction and the depth direction are perpendicular, and the cavity includes an opening formed on the first surface, an internal bottom surface located opposite to the opening in the depth direction, a pair of first internal sides facing each other in the width direction, and a pair of second internal sides facing each other in the stacking direction. Solid-state battery comprising: a ceramic package having a first bottom terminal provided on the inner bottom surface; a second bottom terminal provided on the inner bottom surface so as to be insulated from the first bottom terminal; a first side terminal provided on at least one of the pair of first inner sides and electrically connected to the first bottom terminal; and a second side terminal provided on at least one of the pair of first inner sides and electrically connected to the second bottom terminal, wherein the first electrode layer is in contact with the first bottom terminal and the first side terminal, and the second electrode layer is in contact with the second bottom terminal and the second side terminal.

[0076] According to this disclosure, a simple structure can be used to improve the reliability of the electrical connection between the ceramic package and the battery element.

[0077] (Technical 2) The solid battery according to Technical 1, wherein the first side terminals are provided on each of the pair of first internal side surfaces, and the second side terminals are provided on each of the pair of first internal side surfaces. With this configuration, the reliability of the electrical connection between the ceramic package and the battery element can be further improved.

[0078] (Technology 3) A solid-state battery according to Technology 1 or 2, wherein the pair of second internal surfaces are located in a direction parallel to the stacking direction, and a gap exists between at least one of the pair of second internal surfaces and the battery element in a direction parallel to the stacking direction. Such a gap can absorb dimensional variations of the battery element in the stacking direction.

[0079] (Technical 4) A solid-state battery according to any one of Technical 1 to 3, wherein at least one of the pair of first internal surfaces is provided with an electrically insulating projection at a position facing the solid electrolyte layer. Internal short circuits can be prevented.

[0080] (Technology 5) The solid battery according to Technology 4, wherein the solid electrolyte layer is in contact with the protrusion. With this configuration, the battery element can be firmly fixed to the ceramic package, so that the characteristics of the battery are stable. The effect of suppressing internal short circuits is also further improved.

[0081] (Technical 6) A method for manufacturing a solid-state battery, the solid-state battery comprising: a ceramic package having a cavity formed thereon having a pair of sides parallel to each other and a pair of other sides parallel to each other when viewed from a first surface in plan view; and a battery element disposed within the cavity of the ceramic package and having a pair of sides parallel to each other and a pair of other sides parallel to each other when viewed from a plan view, the battery element comprising a first electrode layer, a solid electrolyte layer, and a second electrode layer, the width direction defined as the direction perpendicular to the stacking direction of the first electrode layer, the solid electrolyte layer, and the second electrode layer and the depth direction of the cavity, the stacking direction and the depth direction being perpendicular to each other, the cavity comprising an opening formed on the first surface, an internal bottom surface located opposite to the opening in the depth direction, a pair of first internal sides facing each other in the width direction, and a pair of second internal sides facing each other in the stacking direction, The ceramic package comprises a first bottom terminal provided on the inner bottom surface, a second bottom terminal provided on the inner bottom surface so as to be insulated from the first bottom terminal, a first side terminal provided on at least one of the pair of first inner sides and electrically connected to the first bottom terminal, and a second side terminal provided on at least one of the pair of first inner sides and electrically connected to the second bottom terminal, and the manufacturing method comprises: manufacturing the battery element such that its dimensions in the width direction are shorter than the distance between the first inner sides; arranging the battery element in the cavity such that the first electrode layer is in contact with the first bottom terminal and the second electrode layer is in contact with the second bottom terminal; and expanding the battery element in the width direction such that a restraining force from the ceramic package acts on the battery element in the width direction, the method for manufacturing a solid battery.

[0082] According to this disclosure, it is possible to manufacture a solid-state battery with improved reliability of the electrical connection between the ceramic package and the battery element.

[0083] (Technical 7) A method for manufacturing a solid battery according to Technical 6, wherein expanding the battery element includes at least one selected from charging the battery element and heating the battery element. With such a method, no special steps are required to fix the battery element in the ceramic package, and manufacturing is simplified.

[0084] (Technical 8) A method for manufacturing a solid battery according to Technical 6 or 7, wherein expanding the battery element includes heating the battery element after charging, charging the battery element after heating, or heating and charging the battery element simultaneously. Performing the two processes of charging and heating simultaneously is more effective from the viewpoint of expanding the battery element. Furthermore, when charging while heating the battery element, the resistance of the battery element decreases due to heating, and the charging time can be significantly shortened compared to room temperature, which is desirable from the viewpoint of productivity of solid batteries.

[0085] The technology disclosed herein is useful for solid-state batteries equipped with ceramic packages.

[0086] 10, 10S Ceramic package 20, 20S Package body 20b Internal bottom surface 20p First internal side surface 20q Second internal side surface 22 First bottom terminal 23 Second bottom terminal 24 First side terminal 25 Second side terminal 27 Protrusion 28 Via conductor 29 External terminal 30 Cover 32 Space 34 Gap 40 Battery element 41 First electrode layer 42 Second electrode layer 43 Solid electrolyte layer 100, 200 Solid battery CA Cavity SD Stacking direction FD Width direction

Claims

1. A ceramic package having a cavity formed therein, having two pairs of sides parallel to each other when viewed from a first surface in plan view; and a battery element disposed within the cavity and having two pairs of sides parallel to each other when viewed from a plan view, wherein the battery element includes a first electrode layer, a solid electrolyte layer, and a second electrode layer, and the width direction is defined as the direction perpendicular to the stacking direction of the first electrode layer, the solid electrolyte layer, and the second electrode layer and the depth direction of the cavity, the stacking direction and the depth direction are perpendicular to each other, and the cavity includes an opening formed on the first surface, an internal bottom surface located opposite to the opening in the depth direction, a pair of first internal sides facing each other in the width direction, and a pair of second internal sides facing each other in the stacking direction. Solid-state battery comprising: a ceramic package having a first bottom terminal provided on the inner bottom surface; a second bottom terminal provided on the inner bottom surface so as to be insulated from the first bottom terminal; a first side terminal provided on at least one of the pair of first inner sides and electrically connected to the first bottom terminal; and a second side terminal provided on at least one of the pair of first inner sides and electrically connected to the second bottom terminal, wherein the first electrode layer is in contact with the first bottom terminal and the first side terminal, and the second electrode layer is in contact with the second bottom terminal and the second side terminal.

2. The solid battery according to claim 1, wherein the first side terminal is provided on each of the pair of first internal side surfaces, and the second side terminal is provided on each of the pair of first internal side surfaces.

3. The solid battery according to claim 1, wherein the pair of second internal surfaces are located in a direction parallel to the stacking direction, and a gap exists between at least one of the pair of second internal surfaces and the battery element in a direction parallel to the stacking direction.

4. The solid battery according to claim 1, wherein at least one of the pair of first internal surfaces is provided with an electrically insulating projection at a position facing the solid electrolyte layer.

5. The solid battery according to claim 4, wherein the solid electrolyte layer is in contact with the protrusion.

6. A method for manufacturing a solid-state battery, wherein the solid-state battery comprises a ceramic package having a cavity formed thereon having a pair of sides parallel to each other and a pair of other sides parallel to each other when viewed from a first surface in plan view, and a battery element disposed within the cavity of the ceramic package and having a pair of sides parallel to each other and a pair of other sides parallel to each other when viewed from a plan view, wherein the battery element includes a first electrode layer, a solid electrolyte layer, and a second electrode layer, and the width direction is defined as the direction perpendicular to the stacking direction of the first electrode layer, the solid electrolyte layer, and the second electrode layer and the depth direction of the cavity, the stacking direction and the depth direction are perpendicular to each other, and the cavity includes an opening formed on the first surface, an internal bottom surface located opposite to the opening in the depth direction, a pair of first internal sides facing each other in the width direction, and a pair of second internal sides facing each other in the stacking direction. The ceramic package comprises a first bottom terminal provided on the inner bottom surface, a second bottom terminal provided on the inner bottom surface so as to be insulated from the first bottom terminal, a first side terminal provided on at least one of the pair of first inner sides and electrically connected to the first bottom terminal, and a second side terminal provided on at least one of the pair of first inner sides and electrically connected to the second bottom terminal, and the manufacturing method comprises: manufacturing the battery element such that its dimensions in the width direction are shorter than the distance between the first inner sides; arranging the battery element in the cavity such that the first electrode layer is in contact with the first bottom terminal and the second electrode layer is in contact with the second bottom terminal; and expanding the battery element in the width direction such that a restraining force from the ceramic package acts on the battery element in the width direction, the method for manufacturing a solid battery.

7. The method for manufacturing a solid battery according to claim 6, wherein expanding the battery element includes at least one selected from charging the battery element and heating the battery element.

8. The method for manufacturing a solid battery according to claim 6, wherein expanding the battery element includes heating the battery element after charging it, charging the battery element after heating it, or heating and charging the battery element simultaneously.

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