All-solid-state battery

Abstract

The all-solid-state battery of the present invention comprises: a stack formed by stacking a positive electrode having a positive electrode collector layer and a positive electrode active material layer and a negative electrode having a negative electrode collector layer and a negative electrode active material layer via a solid electrolyte layer; a pair of positive electrode external electrodes and negative electrode external electrodes, which are arranged on any pair of opposite side surfaces of the stack, the positive electrode collector layer is joined to the positive electrode external electrode, the negative electrode collector layer is joined to the negative electrode external electrode, and in at least one of the positive electrode collector layer or the negative electrode collector layer, the thickness of the portion joined to the positive electrode external electrode or the negative electrode external electrode is thicker than the other portions.

Description

Technical Field

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

[0002] This application claims priority based on Special Application No. 2018-217169 filed in Japan on November 20, 2018, and the contents of which are cited herein. Background Art

[0003] In recent years, the development of electronic technology has attracted great attention, and has realized the miniaturization, lightness, thinness and multifunctionalization of portable electronic devices. Then, for the battery that becomes the power source of electronic devices, it is strongly desired to be miniaturized, lightness, thinness and reliability. At present, in the widely used lithium ion secondary battery, as the medium for making ions move, electrolytes (electrolytes) such as organic solvents are currently used. However, in the battery of the above structure, there is the danger of electrolyte leakage. In addition, the organic solvent used in the electrolyte is a flammable substance, therefore, a safer battery is needed.

[0004] Therefore, as a countermeasure for improving the safety of batteries, it is proposed to use solid electrolytes as electrolytes instead of electrolyte solutions. In addition, the development of all-solid batteries using solid electrolytes as electrolytes and other components also consisting of solids is progressing.

[0005] In general, all-solid-state batteries are classified into two types: thin-film type and bulk type. The thin-film type can be produced by thin-film technology such as PVD method or sol-gel method. In addition, the bulk type can be produced by powder molding of sulfide-based solid electrolytes with low active material or grain boundary resistance. In the thin-film type, it is difficult to thicken the active material and stack multiple layers, so there are problems such as small capacity and high manufacturing cost. On the other hand, the bulk type uses a sulfide-based solid electrolyte, so hydrogen sulfide is produced when the sulfide-based solid electrolyte reacts with water. Therefore, it is difficult to handle in the atmosphere, and the battery needs to be made in a glove box that manages the dew point. In this way, in thin-film type and bulk type all-solid-state batteries, problems in safety and manufacturing environment become technical problems.

[0006] On the other hand, the process technology of stacked components can be applied to oxide-based solid electrolytes that are chemically stable in the atmosphere, and for example, a stacked all-solid battery is disclosed in Patent Document 1. The all-solid battery is a stacked all-solid battery in which positive electrode units and negative electrode units are alternately stacked via ion-conductive inorganic material layers, characterized in that: the positive electrode unit has a positive electrode active material layer on both sides of the positive electrode collector layer, and the above-mentioned negative electrode unit has a negative electrode active material layer on both sides of the negative electrode collector layer, and at least one of the positive electrode collector layer and the negative electrode collector layer is composed of any metal of Ag, Pd, Au and Pt, or an alloy containing any one of Ag, Pd, Au and Pt, or a mixture of two or more metals and alloys selected from them, and is fired together.

[0007] In addition, at different end faces of the above-mentioned stacked all-solid battery, there are respectively a positive lead-out electrode connected to the positive electrode collector layer (hereinafter referred to as the positive electrode external electrode) and a negative lead-out electrode connected to the negative electrode collector layer (hereinafter referred to as the negative electrode external electrode).

[0008] However, the above-mentioned stacked all-solid-state battery sometimes undergoes peeling at the joining surfaces (including direct joining and joining via other layers) between the positive electrode external electrode and the positive electrode collector layer and between the negative electrode external electrode and the negative electrode collector layer due to the volume expansion of the active material generated by the charge and discharge reaction, and the cycle characteristics may be reduced.

[0009] Prior art literature

[0010] Patent Literature

[0011] Patent Document 1: International Publication No. 2007 / 135790 Summary of the invention

[0012] Technical problem to be solved by the invention

[0013] The present invention is made to solve the above-mentioned technical problems, and provides an all-solid-state battery with excellent cycle characteristics.

[0014] Technical solutions for solving technical problems

[0015] The first embodiment of the present invention relates to an all-solid-state battery, which includes: a stack formed by stacking a positive electrode having a positive electrode collector layer and a positive electrode active material layer and a negative electrode having a negative electrode collector layer and a negative electrode active material layer via a solid electrolyte layer; and a pair of positive electrode external electrodes and negative electrode external electrodes, which are arranged on any pair of opposite sides of the stack, the positive electrode collector layer is joined to the positive electrode external electrode, and the negative electrode collector layer is joined to the negative electrode external electrode, and in at least one of the positive electrode collector layer or the negative electrode collector layer, the thickness of the portion joined to the positive electrode external electrode or the negative electrode external electrode is thicker than the other portions.

[0016] The second embodiment of the present invention relates to an all-solid-state battery, which comprises: a stacked body, which is formed by stacking a positive electrode having a positive electrode collector layer and a positive electrode active material layer and a negative electrode having a negative electrode collector layer and a negative electrode active material layer with a solid electrolyte layer in between; and a pair of positive electrode external electrodes and negative electrode external electrodes, which are arranged on any pair of opposite side surfaces of the stacked body, the positive electrode collector layer is joined to the positive electrode external electrode, and the negative electrode collector layer is joined to the negative electrode external electrode, and the thickness of the portion of at least one of the positive electrode collector layer or the negative electrode collector layer that is joined to the positive electrode external electrode or the negative electrode external electrode is thicker than the other portions.

[0017] When the average thickness of the enlarged joint portion, which is the joined portion, is t1 and the average thickness of the non-joined portion, which is a portion other than the enlarged joint portion, is t2, the formula (1) is satisfied.

[0018] 1<(t1 / t2)…(1)

[0019] In addition, the all-solid-state battery according to the above aspect of the present invention preferably satisfies formula (2).

[0020] (t1 / t2)≤4.0…(2)

[0021] Effects of the Invention

[0022] According to the present invention, an all-solid-state battery having excellent cycle characteristics can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a projection diagram showing the appearance of an all-solid-state battery 10 according to one embodiment of the present invention.

[0024] Figure 2 This is a projection diagram showing the appearance of a stacked body 20 of an all-solid-state battery according to an embodiment of the present invention.

[0025] Figure 3 A cross-sectional view along a plane parallel to the side surface 23 and the side surface 24 of the all-solid-state battery 10 according to one embodiment of the present invention is shown.

[0026] Figure 4A Indicates that Figure 3 This is an enlarged view for explaining the positive electrode 30 in the same cross section.

[0027] Figure 4B Indicates that Figure 3 This is an enlarged view for explaining the negative electrode 40 in the same cross section.

[0028] Figure 5 A cross-sectional view parallel to the side surface 23 and the side surface 24 of an all-solid-state battery 10 according to another embodiment of the present invention is shown.

[0029] Figure 6 FE-SEM photograph of a vertical cross section of the all-solid-state battery of Example 6 with respect to the positive external electrode and the negative external electrode.

[0030] Figure 7 FE-SEM photograph of a vertical cross section of the all-solid-state battery of Comparative Example 1 with respect to the positive external electrode and the negative external electrode. DETAILED DESCRIPTION

[0031] Hereinafter, the all-solid battery of the present invention will be described in detail with reference to the accompanying drawings as appropriate. The accompanying drawings used in the following description are sometimes enlarged representations of the features for the sake of convenience in order to facilitate the understanding of the features of the present invention. Therefore, the dimensional ratios of the components recorded in the accompanying drawings are sometimes different from the actual ones. The materials, dimensions, etc. illustrated in the following description are examples, and the present invention is not limited to these, and can be appropriately changed and implemented within the scope of not changing its purpose.

[0032] (First Embodiment)

[0033] First, the first embodiment of the present invention is described. In this embodiment, Figure 1 As shown, the all-solid battery 10 includes a laminate 20, a positive external electrode 60, and a negative external electrode 70. Figure 2 As shown, the laminate 20 of this embodiment is a hexahedron having four side surfaces 21, 22, 23, 24, an upper surface 25, and a lower surface 26. In addition, a positive external electrode 60 and a negative external electrode 70 are formed on any pair of opposing side surfaces. Figure 1 In one embodiment of the all-solid-state battery 10, Figure 2 A positive external electrode 60 is formed on the side surface 21 of the stacked body 20 , and a negative external electrode 70 is formed on the side surface 22 .

[0034] like Figure 3As shown in the cross-sectional view of the laminated body 20, in the laminated body 20, the positive electrode 30 and the negative electrode 40 are stacked with the solid electrolyte layer 50 interposed therebetween, and the positive electrode 30 has a positive electrode collector layer 31 and a positive electrode active material layer 32. The negative electrode 40 has a negative electrode collector layer 41 and a negative electrode active material layer 42. In addition, an edge layer 80 having the same thickness as the positive electrode 30 and an edge layer 80 having the same thickness as the negative electrode 40 are formed between the positive electrode 30 and the negative electrode external electrode 70, and between the negative electrode 40 and the positive electrode external electrode 60, respectively. In addition, the positive electrode 30 is electrically bonded to the positive electrode external electrode 60 via the side surface 21, and the negative electrode 40 is electrically bonded to the negative electrode external electrode 70 via the side surface 22.

[0035] The electrical connection is performed by connecting the positive electrode collector layer of the positive electrode to the positive electrode external electrode. Similarly, the negative electrode collector layer of the negative electrode is connected to the negative electrode external electrode.

[0036] As explained in the following description, either or both of the positive electrode active material and the negative electrode active material are sometimes collectively referred to as active materials, either or both of the positive electrode collector layer 31 and the negative electrode collector layer 41 are collectively referred to as collector layers, either or both of the positive electrode active material layer 32 and the negative electrode active material layer 42 are collectively referred to as active material layers, either or both of the positive electrode and the negative electrode are collectively referred to as electrodes, and either or both of the positive electrode external electrode 60 and the negative electrode external electrode 70 are collectively referred to as external electrodes.

[0037] like Figure 4A As shown, the thickness of the portion 31A of the positive electrode collector layer 31 that is bonded to the positive external electrode 60 is thicker than the average thickness of the portion 31B other than the portion 31A. By setting the positive electrode collector layer 31 to the above-mentioned structure, the bonding area between the positive electrode collector layer 31 and the positive external electrode 60 can be increased, and the bonding strength between the positive external electrode 60 and the positive electrode collector layer 31 can be improved. Hereinafter, the portion 31A is sometimes referred to as the expanded bonding portion 31A, and the portion 31B is sometimes referred to as the non-expanded portion 31B. When the thickness (length in the thickness direction) of the end face 31b on the inner side of the stack 20 opposite to the end face 31a of the positive electrode collector layer 31 exposed on the side surface 21 is set to t 2b When the thickness of the expanded joint portion 31A at any position is greater than the thickness t of the end surface 31b 2b Thick. Figure 4A As shown, not only in the case of a structure in which the thickness of the expanded joint 31A changes sharply relative to the thickness of the non-expanded portion 31B, but also in the case of a structure in which the thickness of the expanded joint 31A changes gradually and continuously or changes in stages, or a structure in which these situations are combined, the thickness of the expanded joint at any position is thicker than the end face on the inner side of the stack.

[0038] In addition, if Figure 4BAs shown, the thickness of the portion 41A of the negative electrode collector layer 41 that is bonded to the negative electrode external electrode 70 is thicker than the average thickness of the portion 41B other than the portion 41A. By setting the negative electrode collector layer 41 to the above-mentioned structure, the bonding area between the negative electrode collector layer 41 and the negative electrode external electrode 70 can be increased, and the bonding strength between the negative electrode external electrode 70 and the negative electrode collector layer 41 can be improved. Hereinafter, as in the case of the negative electrode collector layer 41, the portion 41A is sometimes referred to as the enlarged bonding portion 41A, and the portion 41B is sometimes referred to as the non-enlarged portion 41B.

[0039] The average thickness of the collector layer in the expanded joint is defined as t1. In addition, the average thickness of the collector layer in the non-expanded portion is defined as t2. In addition, regarding the "average thickness" here, 20 parts are extracted by dividing the cross section parallel to the side 23 and the side 24 21 times from the side 23 to the side 24 at equal intervals, and the average thickness of the collector layer at the parts exposed to the side 21 and the side 22 and the average thickness of the collector layer at the parts not exposed to the side in the cross section of the 20 parts are measured by cross-sectional SEM observation, and then calculated based on the respective average values. In addition, Figure 3 Unlike the all-solid battery 10 described above, in the case of an all-solid battery in which a plurality of positive electrodes 30 and negative electrodes 40 are stacked, a plurality of collector layers are present at the portion exposed to the side and a plurality of collector layers are present at the portion not exposed to the side on one cross section. In this case, among all the collector layers at one cross section, the thickness of the collector layer at the portion exposed to the side and the thickness of the collector layer at the portion not exposed to the side are measured at the cross sections of 20 portions, and then their average values ​​are calculated, thereby similarly obtaining t1 and t2.

[0040] Preferably, the relationship between t1 and t2 satisfies 1.0<(t1 / t2), in other words, t1 is set thicker than t2. By setting the above structure, the bonding area between the collector layer and the external electrode can be increased, and the bonding strength between the external electrode and the collector layer can be improved. Therefore, relative to the volume expansion and contraction of the active material layer accompanying the charge and discharge reaction, the peeling of the external electrode and the collector layer can be suppressed, and an all-solid battery with excellent cycle characteristics can be obtained. When t1 / t2 is less than 1.0, the bonding area between the external electrode and the collector layer is small, and therefore, cracks or peeling sometimes occur at the bonding surface due to volume expansion / contraction.

[0041] In addition, it is more preferable that the relationship between t1 and t2 satisfies (t1 / t2)≤4.0. When t1 / t2 is set to a value exceeding 4.0, although the bonding area between the external electrode and the collector layer increases, fine cracks are formed due to excessive roller grinding, and therefore, the internal resistance increases, sometimes reducing the cycle characteristics.

[0042] Preferably, the solid electrolyte layer 50 of the all-solid-state battery 10 of this embodiment contains at least an oxide-based lithium ion conductor, and one or both of the positive electrode active material layer 32 and the negative electrode active material layer 42 contain at least an oxide-based lithium ion conductor. Preferably, the edge layer contains at least an oxide-based lithium ion conductor, similarly to the solid electrolyte layer. In addition, Figure 3 In the embodiment, both the positive electrode active material layer 32 and the negative electrode active material layer 42 contain an oxide-based lithium ion conductor, but it may be contained in only one of them. Figure 3 The examples in which the same reference numerals are marked and the same materials are used are shown above. Of course, the invention is not limited to this and the same materials may not be used.

[0043] (Solid Electrolyte)

[0044] The solid electrolyte layer 50 of the all-solid-state battery of the present embodiment is not particularly limited, and for example, a common solid electrolyte material such as an oxide-based lithium ion conductor having a sodium superion conductor type (NASICON type), garnet type, or perovskite type crystal structure can be used. As a lithium ion conductor having a sodium superion conductor type crystal structure, there can be cited: an ion conductor having a sodium superion conductor type crystal structure containing at least Li, M (M is at least one of Ti, Zr, Ge, Hf, and Sn), P, and O; and an ion conductor having a garnet type crystal structure or a garnet type-like structure containing at least Li, Zr, La, and O; and at least one of an ion conductor having a perovskite type structure containing at least Li, Ti, La, and O. That is, one of these ion conductors can be used, or a plurality of them can be mixed and used.

[0045] As the solid electrolyte material of this embodiment, it is preferred to use a lithium ion conductor having a sodium superion conductor type crystal structure, for example, preferably containing LiZr2(PO4)3, Li 1.3 Al 0.3 Ti 1.7 (PO4)3、Li 1.5 Al 0.5 Ge 1.5 (PO4)3 represents a solid electrolyte material. LiZr2(PO4)3 is preferably replaced by Ca or Y, and can be exemplified by Li 1.4 Ca 0.2 Zr 1.8 (PO4)3、Li 1.15 Y 0.15 Zr 1.85 (PO4)3.

[0046] (Positive electrode active material and negative electrode active material)

[0047] As described above, the positive electrode active material layer 32 and the negative electrode active material layer 42 of the all-solid-state battery 10 of this embodiment, as active materials of the positive electrode active material and the negative electrode active material, contain at least a known compound that can absorb and release lithium ions. In addition, it may also contain a conductive aid, an ion conductive aid, a binder, etc. The positive electrode active material and the negative electrode active material are preferably capable of effectively inserting and removing lithium ions.

[0048] The positive electrode active material and the negative electrode active material are, for example, transition metal oxides and transition metal composite oxides. Specifically, the positive electrode active material and the negative electrode active material are, for example, lithium manganese composite oxide Li2Mn a Ma 1-a O3 (0.8≤a≤1, Ma=Co, Ni), lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganese oxide (LiMn2O4) with spinel structure, with the general formula: LiNi x Co y Mn z O2 (x + y + z = 1, 0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1), lithium vanadium compound (LiV2O5), olivine-type LiMbPO4 (wherein Mb is one or more elements selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, Zr), lithium vanadium phosphate (Li3V2(PO4)3 or LiVOPO4), Li excess solid solution positive electrode represented by Li2MnO3-LiMcO2 (Mc = Mn, Co, Ni), lithium titanate (Li4Ti5O 12 ), titanium oxide (TiO2), Li s Ni t Co u Al v Composite metal oxides represented by O2 (0.9<s<1.3, 0.9<t+u+v<1.1), etc.

[0049] The positive electrode active material and the negative electrode active material of this embodiment preferably contain a phosphate compound as the main component, for example, any one or more of lithium vanadium phosphate (LiVOPO4, Li3V2(PO4)3, Li4(VO)(PO4)2), lithium vanadium pyrophosphate (Li2VOP2O7, Li2VP2O7) and Li9V3(P2O7)3(PO4)2, and particularly preferably one or both of LiVOPO4 and Li3V2(PO4)3.

[0050] The main component of this embodiment means that the ratio of the phosphate compound in the positive electrode active material layer and the negative electrode active material layer to the total positive electrode active material and the negative electrode active material is greater than 50 parts by weight, and preferably the ratio of the phosphate compound is 80 parts by weight or more.

[0051] In addition, these positive electrode active materials and negative electrode active materials may also replace part of each element with a different type of element, or change the stoichiometric composition. LiVOPO4 and Li3V2(PO4)3 preferably have lithium deficiency. x VOPO4(0.94≤x≤0.98) or Li x V2(PO4)3(2.8≤x≤2.95) is more preferred.

[0052] In addition, as the negative electrode active material, for example, Li metal, Li-Al alloy, Li-In alloy, carbon, silicon (Si), silicon oxide (SiOx), lithium titanate (Li4Ti5O 12 ), titanium oxide (TiO2).

[0053] Here, there is no clear distinction between the active materials constituting the positive electrode active material layer 32 and the negative electrode active material layer 42. By comparing the potentials of the compounds in the positive electrode active material layer and the compounds in the negative electrode active material layer, the compound with a higher potential can be used as the positive electrode active material, and the compound with a lower potential can be used as the negative electrode active material. In addition, if the compound has both lithium ion release and lithium ion absorption, the material constituting the positive electrode active material layer 32 and the negative electrode active material layer 42 can also use the same material.

[0054] Examples of the conductive additive include carbon materials such as carbon black, acetylene black, Ketjen black, carbon nanotubes, graphite, graphene, and activated carbon, and metal materials such as gold, silver, palladium, platinum, copper, and tin.

[0055] The ion-conducting auxiliary agent is, for example, a solid electrolyte. As the solid electrolyte, for example, the same material as that used for the solid electrolyte layer 50 can be used specifically.

[0056] When a solid electrolyte is used as the ion-conducting auxiliary agent, the ion-conducting auxiliary agent and the solid electrolyte used for the solid electrolyte layer 50 are preferably made of the same material.

[0057] (Positive electrode collector and negative electrode collector)

[0058] The materials constituting the positive electrode collector layer 31 and the negative electrode collector layer 41 of the all-solid battery 10 of this embodiment preferably use materials with high electrical conductivity, for example, silver, palladium, gold, platinum, aluminum, copper, nickel, etc. are preferably used. In particular, copper is difficult to react with oxide-based lithium ion conductors and has the effect of reducing the internal resistance of the all-solid battery, so it is preferred. The materials constituting the positive electrode collector layer 31 and the negative electrode collector layer 41 can use the same material or different materials.

[0059] In addition, the positive electrode current collector layer 31 and the negative electrode current collector layer 41 of the all-solid-state battery 10 of the present embodiment preferably contain a positive electrode active material and a negative electrode active material, respectively.

[0060] The positive electrode current collector layer and the negative electrode current collector layer preferably contain a positive electrode active material and a negative electrode active material, respectively, because adhesion between the positive electrode current collector layer and the positive electrode active material layer and between the negative electrode current collector layer and the negative electrode active material layer is improved.

[0061] The ratio of the positive electrode active material to the negative electrode active material in the positive electrode collector layer 31 and the negative electrode collector layer 41 of the present embodiment is not particularly limited as long as they function as collectors, but the volume ratio of the positive electrode collector to the positive electrode active material, or the negative electrode collector to the negative electrode active material is preferably in the range of 90 / 10 to 70 / 30.

[0062] (Edge layer)

[0063] The edge layer 80 of the all-solid battery 10 of the present embodiment is preferably provided to eliminate the height difference between the solid electrolyte layer 50 and the positive electrode 30 and the height difference between the solid electrolyte layer 50 and the negative electrode 40. Therefore, the edge layer 80 represents the area outside the positive electrode 30. By the presence of such an edge layer 80, the height difference between the solid electrolyte layer 50 and the positive electrode 30 and the negative electrode 40 is eliminated, so that the density of the electrode becomes higher, and it is not easy to produce interlayer peeling (delamination) and warping caused by firing of the all-solid battery 10.

[0064] The material constituting the edge layer 80 preferably includes, for example, the same material as the solid electrolyte layer 50. Therefore, it is preferred to include an oxide-based lithium ion conductor having a sodium superion conductor type, a garnet type, or a perovskite type crystal structure. As lithium ion conductors having a sodium superion conductor type crystal structure, there can be cited: an ion conductor having a sodium superion conductor type crystal structure containing at least Li, M (M is at least one of Ti, Zr, Ge, Hf, and Sn), P, and O; and an ion conductor having a garnet type crystal structure or a garnet type-like structure containing at least Li, Zr, La, and O; and at least one of an ion conductor having a perovskite type structure containing at least Li, Ti, La, and O. That is, one of these ion conductors can be used, or a plurality of them can be mixed and used.

[0065] (Method for manufacturing all-solid-state battery)

[0066] The all-solid-state battery 10 of the present embodiment can be manufactured in the following order. The materials of the positive electrode collector layer 31, the positive electrode active material layer 32, the solid electrolyte layer 50, the negative electrode collector layer 41, the negative electrode active material layer 42, and the edge layer 80 are paste-formed. The method of paste-forming is not particularly limited, for example, the powders of the above-mentioned materials can be mixed into a vehicle liquid to obtain a paste. Here, the vehicle liquid is a general term for the medium in the liquid phase, including solvents, adhesives, etc. The adhesive contained in the paste for molding the raw sheet or the printing layer is not particularly limited, and polyvinyl acetal resin, cellulose resin, acrylic resin, polyurethane resin, vinyl acetate resin, polyvinyl alcohol resin, etc. can be used, and the slurry can contain at least one of these resins.

[0067] The paste may contain a plasticizer. The type of the plasticizer is not particularly limited, and phthalic acid esters such as dioctyl phthalate and diisononyl phthalate may be used.

[0068] By the above method, a positive electrode collector layer paste, a positive electrode active material layer paste, a solid electrolyte layer paste, a negative electrode active material layer paste, a negative electrode collector layer paste, and an edge layer paste were prepared.

[0069] The prepared solid electrolyte layer paste is applied to a substrate such as polyethylene terephthalate (PET) at a desired thickness, and dried as needed to prepare a solid electrolyte raw sheet (solid electrolyte layer) 50. The method for preparing the solid electrolyte raw sheet is not particularly limited, and a known method such as a doctor blade method, a die coating method, a comma coating method, and a gravure coating method can be used. Next, the positive electrode active material layer 32, the positive electrode collector layer 31, and the positive electrode active material layer 32 are sequentially printed and stacked on the solid electrolyte raw sheet (solid electrolyte layer) 50 by screen printing to form a positive electrode 30. In addition, in order to fill the height difference between the solid electrolyte raw sheet (solid electrolyte layer) 50 and the positive electrode 30, an edge layer 80 is formed by screen printing in the area outside the positive electrode to prepare a positive electrode unit.

[0070] The negative electrode unit can also be produced by the same method as the positive electrode unit.

[0071] Furthermore, the positive electrode unit and the negative electrode unit are biased and stacked in a manner that one end of each unit is alternately inconsistent, and a plurality of stacked substrates containing components of the all-solid-state battery are prepared. In addition, regarding the stacked substrate, an outer layer can be provided on both main surfaces of the stack as required. The outer layer can use the same material as the solid electrolyte, and a green sheet for the solid electrolyte can be used.

[0072] The above-mentioned manufacturing method is a method for manufacturing a parallel type all-solid battery 10, but the manufacturing method of a series type all-solid battery can be stacked in a manner that one end of the positive electrode and one end of the negative electrode are consistent, that is, without bias. In the all-solid battery, each collector layer is bonded to the external electrode using two opposite end faces, but from the viewpoint of improving the bonding strength, it is preferred to have an enlarged bonding portion on each of its two end face sides.

[0073] The produced laminated substrate can then be pressed together with a die press, warm isostatic press (WIP), cold isostatic press (CIP), static press, etc. to improve adhesion. Pressing is preferably performed while heating, for example, at 40 to 95°C.

[0074] The produced laminated substrate can be cut into the unfired laminated body 20 of the all-solid-state battery using a cutting device.

[0075] The laminated body 20 of the all-solid battery is sintered by debinding and firing. The debinding and firing can be performed at a temperature of 600° C. to 1000° C. in a nitrogen atmosphere. The holding time of the debinding and firing is, for example, 0.1 to 6 hours.

[0076] (Method for Forming Expanded Joint)

[0077] The enlarged joint portion can be formed using a known molding or processing method. As an example, there is a method in which the collector layers 31 and 41 exposed on the side surfaces 21 and 22 of the stacked body 20 are extended in the stacking direction by barrel polishing.

[0078] The drum grinding can be performed on the unfired all-solid battery stack 20, or on the fired all-solid battery stack 20. The drum grinding method includes dry drum grinding without water and wet drum grinding with water. In the case of wet drum grinding, an aqueous solution such as water is added to the drum grinder.

[0079] The roller treatment conditions are not particularly limited and can be adjusted as appropriate, and are not limited thereto as long as t1 can be increased within a range where defects such as cracks and chips do not occur in the laminate.

[0080] First, the sintered laminate 20, abrasive material, and buffer material are placed in the drum of the drum grinder, and the drum is rotated, thereby increasing the average thickness of t1. It can also be performed at 30 to 100 rpm as a rotation speed, and the processing time is about 1 to 5 hours. In addition, if the thickness of the collector layer extending to the side due to the collision of the laminates becomes large, the amount of water, abrasive material, and buffer material placed in the drum can be reduced, or the placement in the drum can be omitted.

[0081] The shape of the drum used in the drum grinding is preferably cylindrical or polygonal, and the shape can be appropriately changed according to the grinding conditions. In addition, the size of the drum is not particularly limited.

[0082] As the grinding material put into the drum, media such as aluminum oxide, zirconium oxide, polymers, and metals can be used. Regarding the size of the medium used as the grinding material, its diameter is preferably not less than 0.5 mm and not more than 10 mm. As the buffer material, for example, solutions such as water and organic solvents, proteins, polysaccharides, polymers, and other organic fine powders can be used. Regarding the size of the medium used as a buffer material for organic fine powders, its diameter is preferably not less than 0.01 mm and not more than 1 mm. Grinding materials and buffer materials can be used alone or in combination. In addition, the amount of the laminate, grinding material, and buffer material put into the drum is preferably not less than 80% and not more than 100% of the drum volume, and the solid content of the grinding material and buffer material is preferably not less than 50% and not more than 70% of the drum volume.

[0083] In addition, in order to effectively draw current from the stack 20 of the all-solid-state battery, external electrodes (positive external electrode 60 and negative external electrode 70) can be provided. The external electrodes form a positive external electrode 60 and a negative external electrode 70 on any pair of opposite sides of the stack 20. As methods for forming the external electrodes, sputtering, screen printing or dip coating can be cited. In the screen printing method and the dip coating method, an external electrode paste containing metal powder, resin and solvent is prepared and formed as an external electrode 6. Next, a sintering process for removing the solvent and a plating process for forming a terminal electrode on the surface of the external electrode are performed. On the other hand, in the sputtering method, the external electrode and the terminal electrode can be directly formed, so a sintering process and a plating process are not required.

[0084] The laminate 20 of the all-solid battery can be sealed in a button cell, for example, to improve moisture resistance and impact resistance. The sealing method is not particularly limited, and for example, the laminate after firing can be sealed with a resin. In addition, the laminate can be sealed by applying or dipping an insulating paste such as Al2O3 around the laminate and heat-treating the insulating paste.

[0085] (Second Embodiment)

[0086] Next, a full solid battery according to a second embodiment of the present invention will be described. In the description of the second embodiment, the same reference numerals are given to the same structures as those of the full solid battery 10 according to the first embodiment, and the description thereof will be omitted.

[0087] In the all-solid-state battery of the present embodiment, only the current collector layer of either the positive electrode or the negative electrode has the enlarged junction portion. Figure 5In the example shown, only the positive electrode 30 has an enlarged joint in the positive electrode collector layer 31, and the negative electrode 40 does not have an enlarged joint in the negative electrode collector layer 41. Even with the above-mentioned structure, as in the first embodiment, the stress load caused by volume expansion is alleviated compared with the past, cracks in the all-solid battery are suppressed, and an all-solid battery with excellent cycle characteristics can be provided. In addition, Figure 5 In the example shown, only the positive electrode has an enlarged joint portion in the current collector layer. However, even if only the negative electrode has an enlarged joint portion in the current collector layer, the same effect can be achieved.

[0088] In the present embodiment, the side 21 of the stack 20 is coated with a coating material and then subjected to roller grinding, which is different from the first embodiment. By coating one side 21 with a coating material, it is possible not to grind the side 21 during roller grinding. Therefore, the thickness of the positive electrode collector layer exposed to the side 21 can be unchanged, and only the thickness of the negative electrode collector layer exposed to the side 22 can be changed. In addition, the coating material is not particularly limited, and polyvinylidene fluoride (PVdF) and the like can be used. After roller grinding with the coating material, the coating material can be cleaned and removed with an organic solvent. The organic solvent is not particularly limited, and N-methyl-2-pyrrolidone and the like can be cited.

[0089] As mentioned above, although embodiment of this invention was demonstrated in detail, it is not limited to the said embodiment, Various deformation|transformation is possible.

[0090] Example

[0091] Hereinafter, the present invention will be described in more detail using examples and comparative examples based on the above-mentioned embodiments, but the present invention is not limited to these examples. In addition, the "parts" of the amount of materials added in the preparation of the paste refer to "parts by mass" unless otherwise specified.

[0092] (Example 1)

[0093] (Production of positive electrode active material and negative electrode active material)

[0094] As the positive electrode active material and the negative electrode active material, lithium vanadium phosphate (Li3V2(PO4)3) produced by the following method was used. As a production method, Li2CO3, V2O5, and NH4H2PO4 were used as the starting materials, and wet mixing was performed for 16 hours using a ball mill. The powder obtained after dehydration and drying was pre-fired at 850°C in a nitrogen-hydrogen mixed gas for 2 hours. The pre-fired product was wet-crushed using a ball mill, and then dehydrated and dried to obtain positive electrode active material powder and negative electrode active material powder. The composition and crystal structure of the produced powder were confirmed to be Li3V2(PO4)3 using ICP emission spectrometry and X-ray diffraction equipment.

[0095] (Preparation of paste for positive electrode active material layer and paste for negative electrode active material layer)

[0096] Regarding the paste for the positive electrode active material layer and the paste for the negative electrode active material layer, 15 parts of ethyl cellulose as a binder and 65 parts of dihydropinene as a solvent were added to 100 parts of Li3V2(PO4)3 powder, mixed and dispersed to obtain the paste for the positive electrode active material layer and the paste for the negative electrode active material layer.

[0097] (Preparation of paste for solid electrolyte layer)

[0098] As the solid electrolyte, lithium aluminum titanium phosphate (Li 1.3 Al 0.3 Ti 1.7 (PO4)3). In its production method, Li2CO3, Al2O3, TiO2, and NH4H2PO4 are used as the starting materials, and after wet mixing for 16 hours using a ball mill, dehydration and drying are performed. Then, the obtained powder is pre-calcined at 800°C in the atmosphere for 2 hours. After pre-calcination, the powder is wet-pulverized for 16 hours using a ball mill, and then dehydrated and dried to obtain a solid electrolyte powder.

[0099] (X-ray diffraction pattern)

[0100] The crystal structure of the solid electrolyte powder was determined by X-ray diffraction pattern using CuKα radiation. The obtained X-ray diffraction pattern was analyzed, and the result showed the same X-ray diffraction pattern as LiTi2(PO4)3 (lithium titanium phosphate) in ICDD card 35-0754, thus confirming that it was a crystal structure of sodium superion conductor type.

[0101] Next, 100 parts of ethanol and 200 parts of toluene as solvents were added to the powder and wet mixed using a ball mill. Then, 16 parts of a polyvinyl butyral-based binder and 4.8 parts of butyl benzyl phthalate were further added and mixed to prepare a paste for a solid electrolyte layer.

[0102] (Fabrication of Sheet for Solid Electrolyte Layer)

[0103] The solid electrolyte layer paste was formed into a sheet using a PET film as a base material by a doctor blade method to obtain a solid electrolyte layer sheet (solid electrolyte layer) having a thickness of 15 μm.

[0104] (Preparation of paste for positive electrode collector layer and paste for negative electrode collector layer)

[0105] As the positive electrode collector and the negative electrode collector, Cu and Li3V2(PO4)3 are mixed in a volume ratio of 80 / 20, and then 10 parts of ethyl cellulose as a binder and 50 parts of dihydropinene as a solvent are added, mixed and dispersed to prepare a paste for the positive electrode collector layer and a paste for the negative electrode collector layer.

[0106] (The edge layer is made of paste)

[0107] Regarding the edge layer paste, please contact Li 1.3 Al 0.3 Ti 1.7 100 parts of ethanol and 100 parts of toluene as solvents were added to the (PO4)3 powder, and wet mixed using a ball mill. Then, 16 parts of a polyvinyl butyral adhesive and 4.8 parts of butyl benzyl phthalate were added and mixed to prepare a paste for an edge layer.

[0108] (Preparation of external electrode paste)

[0109] Silver powder, epoxy resin, and solvent are mixed and dispersed to prepare a thermosetting external electrode paste.

[0110] Using these pastes, an all-solid-state battery was produced as follows.

[0111] (Fabrication of positive electrode unit)

[0112] On the above-mentioned solid electrolyte layer sheet, a positive electrode active material layer (referred to as the first positive electrode active material layer) with a thickness of 5 μm is formed by screen printing, and dried at 80°C for 10 minutes. Next, a positive electrode collector layer with a thickness of 5 μm is formed by screen printing on the positive electrode active material layer, and dried at 80°C for 10 minutes. A positive electrode active material layer (referred to as the second positive electrode active material layer) with a thickness of 5 μm is further formed on the positive electrode collector layer by screen printing, and dried at 80°C for 10 minutes, thereby making a positive electrode on a solid electrolyte layer sheet. Next, an edge layer 80 with a height substantially in the same plane as the above-mentioned positive electrode is formed on the periphery of one end of the positive electrode by screen printing, and dried at 80°C for 10 minutes. Next, the sheet of the positive electrode unit is obtained by peeling off the PET film.

[0113] (Fabrication of negative electrode unit)

[0114] On the above-mentioned solid electrolyte layer sheet, a negative electrode active material layer (referred to as the first negative electrode active material layer) with a thickness of 5 μm is formed by screen printing, and dried at 80°C for 10 minutes. Next, a negative electrode collector layer with a thickness of 5 μm is formed on the negative electrode active material layer by screen printing, and dried at 80°C for 10 minutes. A negative electrode active material layer with a thickness of 5 μm (referred to as the second negative electrode active material layer) is further formed on the negative electrode collector layer by screen printing, and dried at 80°C for 10 minutes, thereby making a negative electrode on a solid electrolyte layer sheet. Next, an edge layer with a height roughly in the same plane as the negative electrode is formed on the periphery of one end of the negative electrode by screen printing, and dried at 80°C for 10 minutes. Next, the sheet of the negative electrode unit is obtained by peeling off the PET film.

[0115] (Production of Laminated Body)

[0116] The positive electrode unit and the negative electrode unit are alternately biased in a manner that one end of each is inconsistent, and multiple layers are stacked to produce a stacked substrate. Further, multiple solid electrolyte sheets as outer layers are stacked on the two main surfaces of the above-mentioned stacked substrate, and an outer layer of 500μm is set. It is hot-pressed using a molding machine and then cut to produce an unfired all-solid battery stack. Then, the above-mentioned stack is debonded and fired to obtain a stack of all-solid batteries. The above-mentioned firing is heated in nitrogen at a heating rate of 200℃ / hour to a firing temperature of 750℃, maintained at this temperature for 2 hours, and taken out after natural cooling.

[0117] In the above-mentioned laminated body after firing, the average thickness t1 and t2 of the collector layer exposed on the two opposite sides and the collector layer not exposed were measured, and it was confirmed that t1 was 2.1 μm and t2 was 3.0 μm. In addition, regarding the reason why the thickness of the collector layer exposed on the opposite sides of the laminated body after firing is smaller than the thickness of the collector layer not exposed, the collector layer exposed on the side is more susceptible to the heat caused by firing than the collector layer inside the laminated body, and therefore, the thickness of the collector layer exposed on the side is easy to become smaller.

[0118] (Drum grinding)

[0119] The stack is barrel-milled to extend the thickness of the collector layer exposed on two opposing side surfaces, thereby increasing the thickness. The barrel milling is performed in a wet process.

[0120] The above-mentioned stack, water, a zirconia medium with a diameter of 1 mm as a grinding material, and a 30 μm diameter flask powder as a buffer material were put into a drum container at a ratio of 4:1, and rotated at 50 rpm. The drum time was as described in Table 1, and the thickness t1 of the collector layer exposed on the two opposite sides of the stack was extended. Then, drum grinding was performed in a manner such that the thickness t1 of the above-mentioned collector layer became 3.3 μm. Then, after drum grinding, washing and drying were performed to obtain the stack of the all-solid battery of Example 1.

[0121] After the drum grinding, the cross section parallel to the two opposite sides where the current collector is not exposed is extracted by dividing 21 times at equal intervals from the above one side to the opposite side, and the average thickness of the current collector layer at the part exposed to the side and the average thickness of the current collector layer at the part not exposed to the side in the cross section of the 20 parts are measured by cross-sectional SEM observation, and t1 and t2 are calculated respectively. The results are shown in Table 1.

[0122] (External Electrode Forming Step)

[0123] An external electrode paste was applied to two opposing side surfaces where the current collectors were exposed in the barrel-polished all-solid battery stack, and thermally cured at 150° C. for 30 minutes to form a pair of external electrodes.

[0124] (Examples 2 to 7)

[0125] All-solid batteries of Examples 2 to 7 were produced in the same manner as in Example 1 except that the roller grinding time was set to the values ​​described in Table 1 and t1 was adjusted to the thickness shown in Table 1.

[0126] (Example 8)

[0127] Regarding the all-solid-state battery of Example 8, the side of the stack exposed to the negative electrode collector layer was coated with polyvinylidene fluoride (PVdF) and then roller-polished, and only the positive electrode collector layer exposed on the side opposite to the above-mentioned side was adjusted to the thickness shown in Table 1. The all-solid-state battery was produced in the same manner as in Example 4. In addition, after roller grinding, the above-mentioned PVdF was removed by washing with an organic solvent of N-methyl-2-pyrrolidone.

[0128] (Example 9)

[0129] The all-solid-state battery of Example 9 was produced in the same manner as in Example 8 except that the side of the laminate where the negative electrode current collector layer was exposed was coated with PVdF and then barrel-polished.

[0130] (Comparative Example 1)

[0131] The all-solid-state battery of Comparative Example 1 was an all-solid-state battery that was not subjected to barrel polishing.

[0132] (Comparative Example 2)

[0133] The all-solid-state battery of Comparative Example 2 was produced in the same manner as in Example 1 except that the roller grinding time was set to the value described in Table 1 and t1 was adjusted to the thickness shown in Table 1.

[0134] (Battery Evaluation)

[0135] The all-solid-state batteries produced in the present example and the comparative example were capable of evaluating the following battery characteristics.

[0136] [Charge and discharge cycle test]

[0137] The all-solid-state batteries produced in the present embodiment and the comparative example can be evaluated for charge and discharge cycle characteristics by, for example, the charge and discharge conditions shown below. The charge and discharge current is recorded using the C rate. The C rate is recorded as nC (or μA) (n is a numerical value), which refers to the current that can charge and discharge the nominal capacity (μAh) at 1 / n (h). For example, 1C is a charge and discharge current that can charge the nominal capacity in 1h, and if it is 2C, it refers to a charge and discharge current that can charge the nominal capacity in 0.5h. For example, in the case of an all-solid-state battery with a nominal capacity of 100μAh, a current of 0.1C is 10μA (calculation formula 100μA×0.1=10μA). Similarly, a current of 0.2C is 20μA, and a current of 1C is 100μA.

[0138] Regarding the charge and discharge cycle test conditions, constant current charging (CC charging) was performed at a constant current of 0.2C rate at 25°C until the battery voltage reached 1.6V, and then, the battery voltage was discharged at a constant current of 0.2C rate until the battery voltage reached 0V (CC discharge). The above-mentioned charge and discharge was set as 1 cycle, and the discharge capacity retention rate after repeating it for 1000 cycles was evaluated as the charge and discharge cycle characteristics. In addition, the charge and discharge cycle characteristics of this embodiment were calculated according to the following calculation formula.

[0139] Discharge capacity retention rate after 1000 cycles (%) = (discharge capacity after 1000 cycles ÷ discharge capacity after 1 cycle) × 100

[0140] (result)

[0141] As a representative example, FE-SEM images of the cross sections of the all-solid-state batteries of Example 6 and Comparative Example 1 are shown in FIG. Figure 6 and Figure 7 In. Figure 6As described above, it can be confirmed that in Example 6, the thickness of the positive electrode collector layer of the all-solid-state battery exposed on the side of the stack extends in the stacking direction. In addition, although the figure is omitted, it can be confirmed that the negative electrode collector layer also extends in the stacking direction. On the other hand, Figure 7 As described, in the cross-sectional photograph of the all-solid battery of Comparative Example 1, it is not possible to confirm that the thickness of the positive electrode collector layer in the portion exposed to the end face of the stack extends. In addition, although the figure is omitted, it is also possible to confirm that the thickness of the negative electrode collector layer extends in the stacking direction.

[0142] Table 1 shows the results of the cycle characteristics of the all-solid batteries of Examples 1 to 9 and Comparative Examples 1 to 2. In the all-solid batteries of Examples 1 to 7, in which the average thickness t1 of the enlarged joint of the collector layer exposed on the side of the stack is greater than the average thickness t2 of the non-joint portion other than the enlarged joint of the collector layer, it is confirmed that the cycle characteristics are superior to those of the all-solid batteries of the comparative examples, and in particular, when 1.0<t1 / t2≤4.0 is satisfied, a more excellent cycle characteristic is confirmed. In addition, according to the results of the all-solid batteries of Examples 8 to 9, it is confirmed that the effect of the present invention can be obtained even when the average thickness of the enlarged joint of the collector layer exposed on the side is greater than the average thickness t2 of the non-joint portion other than the enlarged joint of the collector layer in either the positive electrode or the negative electrode. On the other hand, in the all-solid batteries of Comparative Examples 1 to 2, in which the average thickness t1 of the enlarged joint of the collector layer exposed on the side is less than the average thickness t2 of the non-joint portion not exposed on the side, the cycle characteristics are low.

[0143] [Table 1]

[0144]

[0145] As mentioned above, although this invention was demonstrated in detail, the said embodiment and Example are only an illustration, and the invention disclosed here includes the example which variously modified and changed the said specific example.

[0146] Explanation of symbols

[0147] 10: all-solid-state battery, 20: laminate, 30: positive electrode, 31: positive electrode collector layer, 32: positive electrode active material layer, 40: negative electrode, 41: negative electrode collector layer, 42: negative electrode active material layer, 50: solid electrolyte layer, 60: positive electrode external electrode; 70: negative electrode external electrode, 80: edge layer.

Claims

1. An all-solid-state battery, characterized in that: include: A laminated body formed by laminating a positive electrode having a positive electrode collector layer and a positive electrode active material layer and a negative electrode having a negative electrode collector layer and a negative electrode active material layer via a solid electrolyte layer; and a pair of positive external electrodes and negative external electrodes, which are provided on any pair of opposite side surfaces of the stacked body, The positive electrode current collector layer and the positive electrode active material layer are bonded to the positive electrode external electrode, the negative electrode current collector layer and the negative electrode active material layer are bonded to the negative electrode external electrode, and at least one end of each current collector layer in the positive electrode current collector layer is bonded to the positive electrode external electrode, and at least one end of each current collector layer in the negative electrode current collector layer is bonded to the negative electrode external electrode, The thickness of the positive electrode collector layer and the negative electrode collector layer at a portion joined to the positive electrode external electrode or the negative electrode external electrode is thicker than that of a non-joined portion, and the ratio is not more than 4.

2. An all-solid-state battery, characterized in that: include: A laminated body formed by laminating a positive electrode having a positive electrode collector layer and a positive electrode active material layer and a negative electrode having a negative electrode collector layer and a negative electrode active material layer via a solid electrolyte layer; and a pair of positive external electrodes and negative external electrodes, which are provided on any pair of opposite side surfaces of the stacked body, The positive electrode current collector layer and the positive electrode active material layer are bonded to the positive electrode external electrode, the negative electrode current collector layer and the negative electrode active material layer are bonded to the negative electrode external electrode, and at least one end of each current collector layer in the positive electrode current collector layer is bonded to the positive electrode external electrode, and at least one end of each current collector layer in the negative electrode current collector layer is bonded to the negative electrode external electrode, The thickness of the positive electrode current collector layer and the negative electrode current collector layer at the portion joined to the positive electrode external electrode or the negative electrode external electrode is thicker than the thickness of the non-joined portion. When the average thickness of the enlarged joint portion as the joined portion is t1 and the average thickness of the non-joined portion as the portion other than the enlarged joint portion is t2, equation (1) is satisfied and equation (2) is satisfied: 1<(t1 / t2)…(1), (t1 / t2)≤4.0…(2).

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