Secondary batteries

Abstract

The aim is to improve the output characteristics and cycle characteristics of laminate-type secondary batteries using gel polymer electrolytes. [Solution] The device comprises electrodes 10, 20, a separator 30, a gel polymer electrolyte 60, and an outer casing 50 that houses the electrodes, the separator, and the gel polymer electrolyte. The electrodes have a positive electrode 10 containing a positive electrode active material 13 and a negative electrode 20 containing a negative electrode active material 23. The positive and negative electrodes are alternately stacked with the separator in between. The separator has a first portion 30a that sandwiches at least one of the electrodes, the positive and the negative, and a second portion 30b that is bent to connect the first portions of the stacked separators. The electrodes have bent outer peripheral portions 10a, 20a that include bent end portions 10d, 20d that are positioned opposite the second portion 30b of the separator. The bent outer peripheral portion of at least one of the electrodes, either the positive or the negative, contains an inorganic solid electrolyte 70.

Description

[Technical Field]

[0001] This disclosure relates to secondary batteries. [Background technology]

[0002] Patent Document 1 discloses a laminate-type secondary battery in which a positive electrode and a negative electrode are stacked between zigzag-folded strip separators. By stacking electrodes using zigzag-folded separators, the process of cutting the separators is eliminated, which allows for miniaturization of manufacturing equipment and improvement of productivity. Patent Document 1 proposes optimizing the distance between the electrode ends and the bent portion of the separator, and providing a certain distance between the electrode ends and the bent portion of the separator, in order to suppress the risk of the electrodes being caught and causing short circuits when the separator deforms due to thermal shrinkage or the like.

[0003] Furthermore, Patent Documents 2 and 3 disclose the use of a gel polymer electrolyte, which is a mixture of a non-aqueous electrolyte and a polymer, as a solid electrolyte for secondary batteries. When a gel polymer electrolyte is used as a solid electrolyte for secondary batteries, safety can be improved by preventing leakage through the gel polymer's retention of the electrolyte and by using non-flammable polymer materials. Patent Document 2 describes controlling the viscosity of the gel polymer electrolyte. Patent Document 3 describes pre-containing microcapsules that act as gelation initiators in the electrolyte, and after injecting the electrolyte, applying heat or pressure to the microcapsules to gradually release the gelation initiators inside. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 7448357 [Patent Document 2] Patent No. 6159199 [Patent Document 3] Patent No. 6279241 [Overview of the project] [Problems that the invention aims to solve]

[0005] When using a gel polymer electrolyte in a laminate-type secondary battery, the electrode and separator laminate is inserted into an outer casing, the electrolyte material is injected, and the outer casing is vacuum-sealed before the electrolyte material gels. During vacuum sealing, the laminate is subjected to constraining pressure from the outer casing, and the electrolyte material is pushed out toward the outer periphery of the electrode, so the amount of electrolyte around the outer periphery of the electrode tends to increase.

[0006] At the outer periphery of the electrode, the heat generated during the heating process to gel the electrolyte material is greater, leading to more advanced gelation and increased viscosity compared to the center. High-viscosity gel inhibits ion transport, resulting in higher ion transport resistance at the outer periphery of the electrode than at the center, causing uneven current density during charging and discharging. This unevenness in current density at the electrode leads to a decrease in the output characteristics of the secondary battery and localized degradation of the active material, resulting in reduced cycle performance.

[0007] In the laminate-type secondary battery described in Patent Document 1, a U-shaped separator bend is provided at a position away from the electrode ends, forming a space surrounded by the electrode ends and the separator bend. Therefore, when a gel polymer electrolyte is used in the laminate-type secondary battery of Patent Document 1, the electrolyte material is held in the space between the electrode ends and the separator bend, and the high-viscosity gel polymer electrolyte tends to accumulate. As a result, when the separator shrinks due to heat, the high-viscosity gel polymer electrolyte is pushed from the separator bend to the outer circumference of the electrode. Consequently, the resistance becomes particularly high in the outer circumference of the electrode connected to the separator bend, and the current density unevenness of the electrode tends to increase.

[0008] When the gel polymer electrolyte described in Patent Document 2 is used in a laminate-type secondary battery, the low-viscosity electrolyte is easily pushed out toward the outer periphery of the electrode due to the constraining pressure of the outer casing, making it difficult to eliminate current density unevenness in the electrode.

[0009] When the gel polymer electrolyte of Patent Document 3 is used in a laminated secondary battery, it is difficult to eliminate the uneven current density of the electrodes because the microcapsules are easily pushed out toward the outer peripheral portion of the electrodes by the restraint pressure of the exterior body. Even if the microcapsules are locally arranged on the electrodes in advance, it is difficult to arrange them locally because they are involved in the flow of the electrolytic solution when the electrolytic solution is injected.

[0010] In view of the above points, an object of the present disclosure is to improve the output characteristics and cycle characteristics in a laminated secondary battery using a gel polymer electrolyte.

Means for Solving the Problems

[0011] To achieve the above object, in one aspect of the present disclosure, an electrode (10, 20), a separator (30), a gel polymer electrolyte (60) having ion conductivity, and an exterior body (50) for housing the electrode, the separator, and the gel polymer electrolyte are provided. The electrode has a positive electrode (10) containing a positive electrode active material (13) and a negative electrode (20) containing a negative electrode active material (23). The positive electrode and the negative electrode are alternately laminated via a separator. The separator has a first portion (30a) sandwiching at least one of the positive electrode and the negative electrode, and a second portion (30b) bent so as to connect the first portions of the laminated separators. The electrode has a bent-side outer peripheral portion (10a, 20a) including bent-side end portions (10d, 20d) positioned to face the second portion (30b) of the separator. An inorganic solid electrolyte (70) is contained in at least one of the bent-side outer peripheral portions of the positive electrode or the negative electrode of the electrode. [[ID=I3]]

[0012] Thereby, it is possible to improve the ion conductivity of the bent-side outer peripheral portion where the gel polymer electrolyte has a high viscosity and is likely to have a large resistance, and to reduce the uneven current density of the electrodes. As a result, the output characteristics and cycle characteristics of the secondary battery can be improved.

[0013] The reference numerals in parentheses of the above components indicate the correspondence with the specific means described in the embodiments described later.

Brief Description of the Drawings

[0014] [Figure 1] Cross-sectional view of a secondary battery according to the first embodiment. [Figure 2] This is a cross-sectional view showing a portion of multiple stacked electrodes. [Figure 3] This is a plan view of the electrode. [Figure 4] This figure shows an embodiment in which a positive electrode material or negative electrode material is mixed with an inorganic solid electrolyte. [Figure 5] This figure shows an embodiment in which the surface of a positive electrode material or a negative electrode material is coated with an inorganic solid electrolyte. [Figure 6] This figure shows an embodiment in which an inorganic solid electrolyte is coated on the surface of the separator. [Figure 7] This is a flowchart showing the manufacturing process of a secondary battery. [Figure 8] This is a diagram illustrating the manufacturing process of the positive and negative electrodes. [Figure 9] This chart shows the output characteristics and cycle characteristics of the examples and comparative examples. [Modes for carrying out the invention]

[0015] Several embodiments for implementing this disclosure are described below with reference to the drawings. In each embodiment, parts corresponding to matters described in a preceding embodiment may be denoted by the same reference numerals, and redundant explanations may be omitted. If only a part of the configuration is described in each embodiment, other parts of the configuration can be applied to other embodiments described in advance. Not only can parts that are explicitly shown to be combinable in each embodiment be combined, but embodiments can also be partially combined even if not explicitly shown, as long as there are no particular problems with the combination.

[0016] (First Embodiment) The first embodiment of this disclosure will be described below with reference to the drawings. The secondary battery 1 of this embodiment is a lithium-ion battery in which lithium ions are conducted as conductive ions.

[0017] As shown in Figure 1, the secondary battery 1 of this embodiment comprises a positive electrode 10, a negative electrode 20, a separator 30, and an outer casing 50. Hereinafter, the positive electrode 10 and the negative electrode 20 will also be referred to as electrodes 10 and 20.

[0018] The secondary battery 1 of this embodiment is configured as a laminate-type secondary battery in which a laminate 40, in which electrodes 10 and 20 and a separator 30 are stacked, is sealed in an outer casing 50. The laminate 40 of electrodes 10 and 20 and separator 30 together with a gel polymer electrolyte 60 constitute a battery cell.

[0019] The electrodes 10 and 20 are formed as flat, plate-like members. Multiple positive electrodes 10 and negative electrodes 20 are provided, and the number of positive electrodes 10 and negative electrodes 20 can be set arbitrarily. Figure 1 shows an example in which two positive electrodes 10 and two negative electrodes 20 are stacked.

[0020] The separator 30 is formed from a porous material such as a porous membrane, woven fabric, or nonwoven fabric made of resin. Examples of materials that can be used for the separator 30 include polyolefin resins such as polypropylene and polyethylene, and nonwoven fabrics such as cellulose, aramid, and polyester.

[0021] The separator 30 may be surface-coated with a dissimilar material. Examples of dissimilar materials include mixtures of ceramic materials such as alumina, titania, boehmite, magnesium hydroxide, and barium sulfate with binders such as PVDF, PTFE, acrylic copolymers, and PVA, and mixtures of resin materials such as meta-aluminium and para-aramid with the above-mentioned binders.

[0022] In this embodiment, the separator 30 is configured as a single strip-shaped member. The strip-shaped separator 30 is formed in a zigzag pattern and has a plurality of flat portions 30a and a plurality of bent portions 30b. Hereinafter, the flat portions 30a of the separator 30 will be referred to as separator flat portions 30a, and the bent portions 30b of the separator 30 will be referred to as separator bent portions 30b. The separator flat portions 30a are the first part of the separator 30, and the separator bent portions 30b are the second part of the separator 30.

[0023] The separator flat portion 30a and the separator bent portion 30b are formed continuously. Adjacent separator flat portions 30a are connected by the separator bent portion 30b.

[0024] Multiple separator flat sections 30a are arranged in parallel to each other. Positive electrodes 10 and negative electrodes 20 are alternately arranged between adjacent separator flat sections 30a. The positive electrode 10 and the negative electrode 20 are each sandwiched between the separator flat sections 30a, and the separator flat sections 30a are sandwiched between the positive electrode 10 and the negative electrode 20. The separator flat section 30a sandwiches at least one of the electrodes of the positive electrode 10 and the negative electrode 20.

[0025] The separator bent portion 30b is formed by bending the separator 30 on the outside of the ends of the plate-shaped electrodes 10 and 20. The separator bent portion 30b is bent so as to connect the stacked separator flat portions 30a. The separator bent portion 30b is positioned at a predetermined distance from the ends of the electrodes 10 and 20. Therefore, a gap is formed between the separator bent portion 30b and the ends of the electrodes 10 and 20.

[0026] The outer casing 50 is composed of two laminate films 51 and 52. The outer edges of the two laminate films 51 and 52 are joined together, forming a housing space inside. The laminate films 51 and 52 are made, for example, by laminating resin layers on both sides of aluminum foil. The housing space of the outer casing 50 houses a laminate 40 of electrodes 10 and 20 and separator 30.

[0027] Inside the outer casing 50, a laminate 40 of electrodes 10 and 20 and a separator 30 is housed, along with an ion-conducting gel polymer electrolyte 60. The gel polymer electrolyte 60 is present from the positive electrode 10 to the negative electrode 20, with the separator 30 in between, and is provided to penetrate into the interior of both the positive electrode 10 and the negative electrode 20. The gel polymer electrolyte 60 is a mixture of a polymer compound having gelling properties and a non-aqueous electrolyte. The gel polymer electrolyte 60 is a polymer compound that retains the non-aqueous electrolyte, possesses moderate plasticity and tackiness, and has ionic conductivity close to that of a non-aqueous electrolyte.

[0028] The electrolyte constituent material, which is the raw material for the gel polymer electrolyte 60, is poured into the outer casing 50, and after sealing the outer casing 50, polymerization proceeds inside the outer casing 50, thereby obtaining the gel polymer electrolyte 60. The electrolyte constituent material contains a non-aqueous electrolyte and monomers that are raw materials for a polymer compound having gelling properties. Polymerization of the monomers contained in the electrolyte constituent material can be started by adding a polymerization initiator to the electrolyte constituent material and heating it at a predetermined temperature.

[0029] By pre-pouring the electrolyte component into the outer casing 50, the electrolyte component penetrates into the interior of the electrodes 10 and 20. In this state, polymerizing the electrolyte component to produce a gel polymer electrolyte 60 allows the electrolyte to be constantly maintained inside the positive electrode 10 and the negative electrode 20, enabling the charge-discharge reaction to proceed smoothly.

[0030] Examples of polymer compounds having gelling properties include fluororesins containing vinylidene fluoride units, acrylic resins containing (meth)acrylic acid and / or (meth)acrylic acid ester units, and polyether resins containing polyalkylene oxide units. Examples of fluororesins containing vinylidene fluoride units include polyvinylidene fluoride, copolymers containing vinylidene fluoride units and hexafluoropropylene units, and copolymers containing vinylidene fluoride units and trifluoroethylene units. In addition, polymer compounds used as polymer electrolytes (for example, compounds having an alkylene oxide structure) may be used.

[0031] The non-aqueous electrolyte contains a lithium salt and a solvent for dissolving the lithium salt. Suitable lithium salts include LiPF6, LiBF4, LiClO4, Li(FSO2)2N, Li(CF3SO2)(FSO2)N, Li(CF3SO2)2N, LiC(CF3SO2)3, LiBF2(C2O4), and LiB(C2O4)2. A single lithium salt may be used, or two or more may be used in combination.

[0032] As a solvent, one or more organic solvents can be used, including cyclic carbonates such as ethylene carbonate, propylene carbonate, vinylene carbonate, and butylene carbonate, or linear carbonates such as ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and dipropyl carbonate (DPC).

[0033] For polymerization initiators, in the case of radical polymerization, for example, 2,2'-azobisbutyronitrile or benzoyl peroxide can be used, while in the case of cationic polymerization, for example, benzenesulfonic acid esters or alkylsulfonium salts can be used. Furthermore, the polymerization initiator may also be anion constituting the electrolyte salt of a non-aqueous electrolyte, or hydrofluoric acid, a by-product, may be used.

[0034] Next, the positive electrode 10 and the negative electrode 20 will be explained using Figures 2 and 3. Figure 2 is a cross-sectional view of the positive electrode 10 and the negative electrode 20. Figure 3 is a plan view of the positive electrode 10 and the negative electrode 20.

[0035] As shown in Figure 3, the positive electrode 10 and negative electrode 20 are substantially rectangular plate-shaped members. As shown in Figures 2 and 3, the positive electrode 10 has three regions consisting of a first positive electrode outer periphery 10a, a second positive electrode outer periphery 10b, and a positive electrode center 10c. The first positive electrode outer periphery 10a, the second positive electrode outer periphery 10b, and the positive electrode center 10c are aligned along a direction connecting the first positive electrode end 10d, which is closer to the separator bend 30b, and the second positive electrode end 10e, which is further away from the separator bend 30b. The direction connecting the first positive electrode end 10d and the second positive electrode end 10e is perpendicular to the direction in which the positive electrode 10 and negative electrode 20 are stacked, and intersects with the separator bend 30b, and is defined as the left-right direction in Figures 2 and 3.

[0036] The outer periphery 10a of the first positive electrode is a region of the positive electrode 10 that includes the first positive electrode end 10d. The outer periphery 10a of the first positive electrode is a region of the positive electrode 10 that includes the first positive electrode end 10d and has a length of 1 / 3 or less of the length of the positive electrode 10 in the direction connecting the first positive electrode end 10d and the second positive electrode end 10e.

[0037] The second positive electrode outer periphery 10b is a region of the positive electrode 10 that includes the second positive electrode end 10e. The second positive electrode outer periphery 10b is a region of the positive electrode 10 that includes the second positive electrode end 10e and has a length of 1 / 3 or less of the length of the positive electrode 10 in the direction connecting the first positive electrode end 10d and the second positive electrode end 10e.

[0038] The positive electrode center 10c is a region located in the central part of the positive electrode 10 in the direction connecting the first positive electrode end 10d and the second positive electrode end 10e, and is a region sandwiched between the first positive electrode outer periphery 10a and the second positive electrode outer periphery 10b.

[0039] The negative electrode 20 has three regions: a first negative electrode outer periphery 20a, a second negative electrode outer periphery 20b, and a negative electrode center 20c. The first negative electrode outer periphery 20a, the second negative electrode outer periphery 20b, and the negative electrode center 20c are aligned in a direction connecting the first negative electrode end 20d, which is closer to the separator bend 30b, and the second negative electrode end 20e, which is further away from the separator bend 30b. The direction connecting the first negative electrode end 20d and the second negative electrode end 20e is the same direction as the direction connecting the first positive electrode end 10d and the second positive electrode end 10e described above.

[0040] The outer periphery 20a of the first negative electrode is a region of the negative electrode 20 that includes the first negative electrode end 20d. The outer periphery 20a of the first negative electrode is a region of the negative electrode 20 that includes the first negative electrode end 20d and has a length of 1 / 3 or less of the negative electrode 20 in the direction connecting the first negative electrode end 20d and the second negative electrode end 20e.

[0041] The second negative electrode outer periphery 20b is a region of the negative electrode 20 that includes the second negative electrode end 20e. The second negative electrode outer periphery 20b is a region of the negative electrode 20 that includes the second negative electrode end 20e and has a length of 1 / 3 or less of the negative electrode 20 in the direction connecting the first negative electrode end 20d and the second negative electrode end 20e.

[0042] The negative electrode center 20c is a region located in the central part of the negative electrode 20 in the direction connecting the first negative electrode end 20d and the second negative electrode end 20e, and is a region sandwiched between the outer periphery 20a of the first negative electrode and the outer periphery 20b of the second negative electrode.

[0043] The outer periphery 10a of the first positive electrode and the outer periphery 20a of the first negative electrode are the bent side outer periphery. The outer periphery 10b of the second positive electrode and the outer periphery 20b of the second negative electrode are the opposite side outer periphery. The center 10c of the positive electrode and the center 20c of the negative electrode are the center. The end 10d of the first positive electrode and the end 20d of the first negative electrode are the bent side ends. The end 10e of the second positive electrode and the end 20e of the second negative electrode are the opposite side ends.

[0044] As described above in "Problems the Invention Aims to Solve," the viscosity of the gel polymer electrolyte 60 increases in the outer periphery 10a and 10b of the positive electrode and the outer periphery 20a and 20b of the negative electrode, which tends to increase the ion transport resistance. In particular, in the outer periphery 10a of the first positive electrode and the outer periphery 20a of the first negative electrode, which are close to the separator bend 30b, the resistance tends to increase as the viscosity of the gel polymer electrolyte 60 increases.

[0045] The positive electrode 10 comprises a positive electrode current collector 11 and a positive electrode material 12. Layers of the positive electrode material 12 are formed on both sides of the positive electrode current collector 11. The negative electrode 20 comprises a negative electrode current collector 21 and a negative electrode material 22. Layers of the negative electrode material 22 are formed on both sides of the negative electrode current collector 21.

[0046] The positive electrode current collector 11 has a positive electrode terminal 11a. The positive electrode terminal 11a is not provided with a positive electrode material 12. The negative electrode current collector 21 has a negative electrode terminal 21a. The negative electrode terminal 21a is not provided with a negative electrode material 22.

[0047] For example, the positive electrode current collector 11 can be made of aluminum, stainless steel, nickel, titanium, or an alloy thereof. For example, the negative electrode current collector 21 can be made of copper, stainless steel, nickel, titanium, or an alloy thereof.

[0048] The positive electrode material 12 contains a positive electrode active material 13 and an inorganic solid electrolyte 70. In the outer periphery 10a of the first positive electrode, the positive electrode material 12 contains both the positive electrode active material 13 and the inorganic solid electrolyte 70. In the outer periphery 10b of the second positive electrode and the central part 10c of the positive electrode, the positive electrode material 12 contains the positive electrode active material 13 but does not contain the inorganic solid electrolyte 70. In other words, the presence or absence of the inorganic solid electrolyte 70, or the content of the inorganic solid electrolyte 70, differs in the outer periphery 10a of the first positive electrode, the outer periphery 10b of the second positive electrode, and the central part 10c of the positive electrode. The thickness of the positive electrode material 12 is preferably 0.02 mm or more and 0.2 mm or less, and more preferably 0.04 mm or more and 0.1 mm or less.

[0049] The negative electrode material 22 contains a negative electrode active material 23 and an inorganic solid electrolyte 70. In the outer periphery 20a of the first negative electrode, the negative electrode material 22 contains both the negative electrode active material 23 and the inorganic solid electrolyte 70. In the outer periphery 20b of the second negative electrode and the central part 20c of the negative electrode, the negative electrode material 22 contains the negative electrode active material 23, but does not contain the inorganic solid electrolyte 70. In other words, the presence or absence of the inorganic solid electrolyte 70, or the content of the inorganic solid electrolyte 70, differs in the outer periphery 20a of the first negative electrode, the outer periphery 20b of the second negative electrode, and the central part 20c of the negative electrode. The thickness of the negative electrode material 22 is preferably 0.02 mm or more and 0.15 mm or less, and more preferably 0.03 mm or more and 0.8 mm or less.

[0050] In the positive electrode 10, the inorganic solid electrolyte 70 can be provided on the positive electrode material 12 in any manner. Similarly, in the negative electrode 20, the inorganic solid electrolyte 70 can be provided on the negative electrode material 22 in any manner.

[0051] For example, as shown in Figure 4, the inorganic solid electrolyte 70 may be dispersed in the positive electrode material 12 together with the positive electrode active material 13, or the inorganic solid electrolyte 70 may be dispersed in the negative electrode material 22 together with the negative electrode active material 23. Also, as shown in Figure 5, the inorganic solid electrolyte 70 may be coated on the surface of the positive electrode active material 13, or the inorganic solid electrolyte 70 may be coated on the surface of the negative electrode active material 23. Furthermore, as shown in Figure 6, the inorganic solid electrolyte 70 may be coated on the positive electrode 10 side surface of the separator 30, or the inorganic solid electrolyte 70 may be coated on the negative electrode 20 side surface of the separator 30.

[0052] The inorganic solid electrolyte 70 has ionic conductivity. In the positive electrode 10, the inorganic solid electrolyte 70 is included in the outer periphery 10a of the first positive electrode, which has high resistance, thereby increasing the ionic conductivity of the outer periphery 10a of the first positive electrode. As a result, the current density unevenness of the positive electrode 10 can be reduced. Similarly, in the negative electrode 20, the inorganic solid electrolyte 70 is included in the outer periphery 20a of the first negative electrode, which has high resistance, thereby increasing the ionic conductivity of the outer periphery 20a of the first negative electrode. As a result, the current density unevenness of the negative electrode 20 can be reduced.

[0053] As the positive electrode active material 13, any material that can be used for the positive electrode active material 13 of a lithium-ion battery can be used. As the positive electrode active material 13, for example, a layered rock salt type active material, an olivine type active material, or a spinel type active material can be used. As the layered rock salt type active material, for example, LiNi x Co y Mn z O2 (NCM), LiNi x Co y Al z O2 (NCA) and other ternary cathode materials can be used. As the olivine type active material, for example, LiFePO4 (LFP), LiMn 1-x Fe x PO4 (LMFP), LiMnPO4 (LMP), LiCoPO4 (LCP), LiNiPO4 (LNP) can be used. As the spinel type active material, for example, LiMn2O4 (LMO), LiNi 0.5 Mn 1.5 O4 (LNMO) can be used.

[0054] As the negative electrode active material 23, any material that can be used for the negative electrode active material 23 of a lithium-ion battery can be used. As the negative electrode active material 23, for example, carbon-based negative electrode materials such as graphite, amorphous carbon, fullerene, carbon nanotubes, lithium metal materials, metal-based negative electrode materials such as silicon and tin, oxide-based negative electrodes such as Nb2O5 and TiO2, or composites thereof can be used.

[0055] As the inorganic solid electrolyte 70 added to the positive electrode material 12 and the negative electrode material 22, for example, a sulfide-based solid electrolyte or an oxide-based solid electrolyte can be used. As the sulfide-based solid electrolyte, for example, an argyrodite type solid electrolyte can be used. As the oxide-based solid electrolyte, for example, a garnet type solid electrolyte, a NASICON type solid electrolyte, a LISICON type solid electrolyte, or a pyrochlore type solid electrolyte can be used. The pyrochlore type solid electrolyte will be described in detail later.

[0056] As an argyrodite-type solid electrolyte, for example, Li6PS5Cl can be used. As a garnet-type solid electrolyte, for example, Li7La3Zr2O 12 (LLZ) can be used. As a NASICON-type solid electrolyte, for example, Li 1.4 Al 0.4 Ti 1.6 (PO4)3(LATP) can be used. As a LISICON-type solid electrolyte, for example, Li 2+2x Zn 1-x GeO4 can be used. As a pyrochlore-type solid electrolyte, for example, Li 1.25 La 0.58 Nb2O6F(LLNOF), Li 1.25 La 0.58 Ta2O6F(LLTOF) can be used. Oxide-based solid electrolytes can suppress partial decomposition due to reaction with the gel polymer electrolyte 60 more effectively than sulfide-based solid electrolytes. For this reason, it is desirable to use an oxide-based solid electrolyte as the inorganic solid electrolyte 70.

[0057] The content of the inorganic solid electrolyte 70 in the positive electrode 10 and the negative electrode 20 may be the same or different. It is desirable that the content of the inorganic solid electrolyte 70 in the positive electrode 10 > negative electrode 20. Since the interfacial resistance between the electrode and electrolyte is greater in the positive electrode 10 than in the negative electrode 20, increasing the content of the inorganic solid electrolyte 70 in the positive electrode 10 compared to the negative electrode 20 can increase the ionic conductivity of the positive electrode 10, thereby more effectively reducing current density unevenness.

[0058] Next, the pyrochlore-type solid electrolyte used as the inorganic solid electrolyte 70 will be described. The pyrochlore-type solid electrolyte in this embodiment has the composition formula "Aa 2-α Ab (1+α) / 3 B2O 7-β X γIt has a pyrochlore structure represented by the above compositional formula. In the above compositional formula, O is an oxygen atom, and Aa, Ab, B, and X represent any element or group. Aa, Ab, and B are each different types of cations, and O and X are each different types of anions. Aa is an alkali metal cation. Pyrochlore-type solid electrolytes contain multiple cations in their composition, consisting of the alkali metal cation Aa and multiple cations Ab and B other than the alkali metal cation Aa. In other words, pyrochlore-type solid electrolytes contain multiple cations in their composition, including the alkali metal cation Aa.

[0059] Pyrochlore-type solid electrolytes have a crystalline structure in which a three-dimensional network of octahedrons composed of BO6 is formed. In BO6, cation B is at the center, with oxygen atoms at its vertices, and these vertices are shared with adjacent BO6 molecules. Within this three-dimensional network of BO6 molecules, hexagonal tunnel structures are formed in which cation A and anion X are arranged.

[0060] In the above compositional formula, 0.6 < α < 2.0, 0 < β ≤ 1, and 0 < γ ≤ 1. A change in α alters the compositional ratio of Aa and Ab, and a change in β and γ alters the compositional ratio of O and X.

[0061] Cation Aa is an alkali metal cation. Any of Li, Na, K, Rb, or Cs can be used as the alkali metal represented by Aa. Alternatively, Mg or H, which are not alkali metals, may be used as cation Aa. In other words, cation Aa contains at least one selected from Li, Na, K, Rb, Cs, Mg, and H. In this embodiment, Li is used as Aa. The composition ratio (2-α) of Aa is in the range of 0 < (2-α) < 1.4.

[0062] The cation Ab contains at least one lanthanide. At least one of La, Ce, Nd, or Sm can be used as the lanthanide represented by Ab. In this embodiment, La is used as Ab. The composition ratio of Ab (1+α) / 3 is in the range of 0.53 < (1+α) / 3 < 1.

[0063] The basic structure of the cation Ab consists of lanthanides, and some of the lanthanides constituting Ab may be substituted with alkaline earth metals (such as Ca, Mg, and Sr). In this embodiment, the pyrochlore-type solid electrolyte has a pyrochlore structure where 0.6 < α < 2.0 and 0 < β ≤ 1. It is thought that the inclusion of lanthanides in this pyrochlore structure creates defects in the crystal structure, thereby improving ionic conductivity. In this embodiment, La is used as Ab.

[0064] In this embodiment, the pyrochlore-type solid electrolyte has a composite cation consisting of lithium metal and a lanthanide, where cation A is located in the compositional formula "A2B2O7" of a typical pyrochlore structure. This is thought to contribute to the improved ionic conductivity of the pyrochlore-type solid electrolyte.

[0065] Cation B is a metallic cation distinct from Aa and Ab, and is a transition metal or a metal selected from group 13 to 15 elements. In the crystal, B forms an octahedron surrounded by six oxygen atoms. As the transition metal represented by B, group 4 or group 5 transition metals can be used, and more specifically, at least one of Nb, Ta, Ti, Zr, Hf, or V can be used. As the group 13 element represented by B, Al, Ga, or In can be used; as the group 14 element, Ge or Sn can be used; and as the group 15 element, Sb or Bi can be used. In this embodiment, Nb or Ta is used as B.

[0066] Anion X is a substituteable anion for the oxygen atoms constituting the pyrochlore structure. X has different electronegativity and polarizability from the oxygen atoms. At least one of O, F, Cl, Br, I, S, OH, or P can be used as the anion represented by X. The composition ratio γ of X is in the range of 0 < γ ≤ 1, and at least some of the oxygen atoms constituting the pyrochlore structure are substituted with X. In this embodiment, F is used as X.

[0067] The pyrochlore-type solid electrolyte of this embodiment has a defect structure in which lattice defects are included in the crystal, as some of the oxygen atoms constituting the pyrochlore structure are replaced by anions with different electronegativity and polarizability from the oxygen atoms. It is believed that the ionic conductivity of the pyrochlore-type solid electrolyte of this embodiment is improved because the pyrochlore structure contains defect structures.

[0068] In the pyrochlore-type solid electrolyte of this embodiment, a portion of Aa and Ab is missing as a defect structure. The composition formula of a typical pyrochlore structure is "A2B2O7", and the composition ratio of cation A is 2. In contrast, in the pyrochlore-type solid electrolyte of this embodiment, the composition ratios of Aa and Ab are "2-α" and "(1+α) / 3", respectively, and since 0.6 < α < 2.0, the sum of the composition ratios of Aa and Ab is less than 2. In other words, in the crystal structure of the pyrochlore-type solid electrolyte of this embodiment, a portion of at least one of Aa and Ab is missing. The composition ratio corresponding to the missing portions of Aa and Ab is (2α-1) / 3.

[0069] In addition to deviations in compositional ratios, defect structures can also be formed by making the sum of the valencies of the cations consisting of Aa, Ab, and B and the anions consisting of O and X in the above compositional formula negative.

[0070] Furthermore, the pyrochlore-type solid electrolyte of this embodiment is a complex anionic compound in which multiple anions such as O and X are contained in the pyrochlore structure. Because the anion represented by X is present in the BO6 coordination octahedron structure, the alkali metal Aa can be located in the center of the space between the BO6 coordination octahedron and the BO6 coordination octahedron without being pushed towards it. Therefore, it is believed that the pyrochlore-type solid electrolyte of this embodiment exhibits high ionic conductivity when used with an electric field applied, such as in a battery.

[0071] Furthermore, since α, β, and γ in the above compositional formula affect lattice defects and ionic conductivity, it is desirable to use them within an appropriate range. Larger values ​​of α, β, and γ increase the defect concentration in the crystal lattice, but beyond a certain amount, the concentration of alkali metals represented by Aa decreases, and the ionic conductivity declines. For this reason, it is desirable to control α within the range of 0.6 < α < 2.0, β within the range of 0 < β ≤ 1, and γ within the range of 0 < γ ≤ 1.

[0072] As a pyrochlore-type solid electrolyte, Li 1.25 La 0.58 Nb2O6F(LLNOF) and Li 1.25 La 0.58 Ta2O6F(LLTOF) can be used as an example. LLNOF and LLTOF use Li as cation Aa, La as cation Ab, and F as anion X, with α=0.75, β=1, and γ=1. LLNOF uses Nb as cation B, while LLTOF uses Ta as cation B.

[0073] The pyrochlore-type solid electrolyte of this embodiment is 1 × 10⁻⁶ -3 Ionic conductivity of S / cm or higher has been achieved. The pyrochlore-type solid electrolyte of this embodiment exhibits significantly higher ionic conductivity than other oxide-type solid electrolytes such as garnet-type oxides.

[0074] Next, the manufacturing method of the secondary battery 1 of this first embodiment will be explained using the flowchart in Figure 7.

[0075] First, as shown in Figure 7, in step S10, an active material slurry preparation step is performed in which electrode active materials (positive electrode active material 13, negative electrode active material 23) are dispersed in a solvent to prepare an active material slurry. The active material slurry prepared with the positive electrode active material 13 is used as the positive electrode material 12 for the outer periphery 10b and the center 10c of the second positive electrode. The active material slurry prepared with the negative electrode active material 23 is used as the negative electrode material 22 for the outer periphery 20b and the center 20c of the second negative electrode.

[0076] Next, in step S11, a mixture slurry preparation step is performed in which a mixture of electrode active materials 13 and 23 and inorganic solid electrolyte 70 is dispersed in a solvent to prepare a mixture slurry. The mixture slurry prepared with positive electrode active material 13 and inorganic solid electrolyte 70 is used as the positive electrode material 12 for the outer periphery 10a of the first positive electrode and the outer periphery 10b of the second positive electrode. The mixture slurry prepared with negative electrode active material 23 and inorganic solid electrolyte 70 is used as the negative electrode material 22 for the outer periphery 20a of the first negative electrode and the outer periphery 20b of the second negative electrode.

[0077] Next, in S12, a slurry coating process is performed in which the active material slurry and the mixed slurry are applied to the positive electrode current collector 11 and the negative electrode current collector 21. On the positive electrode current collector 11, the active material slurry is applied to the parts corresponding to the outer periphery 10b of the second positive electrode and the center 10c of the positive electrode, and the mixed slurry is applied to the part corresponding to the outer periphery 10a of the first positive electrode. On the negative electrode current collector 21, the active material slurry is applied to the parts corresponding to the outer periphery 20b of the second negative electrode and the center 20c of the negative electrode, and the mixed slurry is applied to the part corresponding to the outer periphery 20a of the first negative electrode.

[0078] As shown in Figure 8, the positive electrode current collector 11 and the negative electrode current collector 21 are sized to allow for the simultaneous production of multiple positive electrodes 10 and multiple negative electrodes 20. The positive electrode current collector 11 is coated with slurry equal to the number of positive electrodes 10 required, at predetermined intervals. The negative electrode current collector 21 is coated with slurry equal to the number of negative electrodes 20 required, at predetermined intervals.

[0079] Next, in S13, a drying process is performed to dry the slurry applied to the positive electrode current collector 11 and the negative electrode current collector 21.

[0080] Next, in S14, a punching process is performed in which the positive electrode current collector 11, which has multiple positive electrodes 10 formed on it, is punched out to divide it into multiple positive electrodes 10, and the negative electrode current collector 21, which has multiple negative electrodes 20 formed on it, is punched out to divide it into multiple negative electrodes 20.

[0081] Next, in S15, a lamination process is performed in which the separator 30 is folded in a zigzag pattern, and the positive electrode 10 and the negative electrode 20 are alternately stacked with the separator 30 in between to form a laminate 40.

[0082] Next, in S16, an outer casing insertion process is performed in which the laminate 40 of the positive electrode 10, negative electrode 20, and separator 30 is inserted into the internal space of the outer casing 50. The outer casing 50 is in a state where the outer edges of two laminate films 51 and 52 are joined together, except for the portion into which the laminate 40 is inserted.

[0083] Next, in S17, an electrolyte injection process is performed in which the electrolyte constituent material, which is the raw material for the gel polymer electrolyte 60, is injected into the internal space of the outer casing 50, and in S18, a vacuum sealing process is performed in which the outer casing 50 is vacuum sealed.

[0084] Next, in S19, a gelation process is performed to gel the electrolyte material sealed in the outer casing 50. In the gelation process, polymerization is initiated by heating the electrolyte material to a predetermined temperature, and gelation proceeds.

[0085] Finally, in S20, a performance test is performed on the secondary battery 1 manufactured in steps up to S19, and the secondary battery 1 is completed.

[0086] According to the first embodiment described above, in the positive electrode 10 of the laminate-type secondary battery 1, an inorganic solid electrolyte 70 is provided on the outer peripheral portion 10a of the first positive electrode connected to the separator bent portion 30b. This makes it possible to improve the ionic conductivity of the outer peripheral portion 10a of the first positive electrode, where the gel polymer electrolyte 60 tends to become highly viscous and increase resistance, and to reduce current density unevenness in the positive electrode 10. As a result, the output characteristics and cycle characteristics of the secondary battery 1 can be improved.

[0087] Furthermore, in this first embodiment, an inorganic solid electrolyte 70 is provided on the outer periphery 20a of the first negative electrode connected to the separator bend 30b of the negative electrode 20 of the laminate-type secondary battery 1. This improves the ionic conductivity of the outer periphery 20a of the first negative electrode, where the gel polymer electrolyte 60 tends to become highly viscous and increase resistance, thereby reducing current density unevenness in the negative electrode 20. As a result, the output characteristics and cycle characteristics of the secondary battery 1 can be improved.

[0088] Furthermore, according to this first embodiment, when an oxide-based solid electrolyte is used as the inorganic solid electrolyte 70, partial decomposition due to the reaction between the inorganic solid electrolyte 70 and the gel polymer electrolyte 60 can be suppressed more effectively than when a sulfide-based solid electrolyte is used as the inorganic solid electrolyte 70. Therefore, by using an oxide-based solid electrolyte as the inorganic solid electrolyte 70, current density unevenness between the positive electrode 10 and the negative electrode 20 can be effectively suppressed.

[0089] Furthermore, according to this first embodiment, by using a pyrochlore-type solid electrolyte having high ionic conductivity as the inorganic solid electrolyte 70, the ionic conductivity of the outer periphery 10a of the first positive electrode and the outer periphery 20a of the first negative electrode can be improved, and current density unevenness between the positive electrode 10 and the negative electrode 20 can be effectively suppressed.

[0090] Furthermore, according to this first embodiment, by providing an inorganic solid electrolyte 70 to the positive electrode 10, where the interfacial resistance between the electrode and the electrolyte tends to be large, the ionic conductivity of the positive electrode 10 can be improved, and current density unevenness of the positive electrode 10 can be effectively suppressed.

[0091] Furthermore, according to this first embodiment, by providing an inorganic solid electrolyte 70 in both the positive electrode 10 and the negative electrode 20, the ionic conductivity of both the positive electrode 10 and the negative electrode 20 can be improved, thereby suppressing current density unevenness.

[0092] Furthermore, according to this first embodiment, by increasing the amount of inorganic solid electrolyte 70 in the positive electrode 10 compared to the amount of inorganic solid electrolyte 70 in the negative electrode 20, the ionic conductivity of the positive electrode 10, which tends to have high interfacial resistance between the electrode and the electrolyte, can be preferentially improved, and current density unevenness between the positive electrode 10 and the negative electrode 20 can be effectively suppressed.

[0093] (Second Embodiment) Next, a second embodiment of the present disclosure will be described. Below, only the parts that differ from the first embodiment will be described. In this second embodiment, the configuration of the positive electrode material 12 and the negative electrode material 22 differs from that of the first embodiment.

[0094] In this second embodiment, the positive electrode material 12 contains a positive electrode active material 13 and an inorganic solid electrolyte 70 in the outer periphery 10a of the first positive electrode and the outer periphery 10b of the second positive electrode. In the central part 10c of the positive electrode, the positive electrode material 12 contains the positive electrode active material 13, but does not contain the inorganic solid electrolyte 70.

[0095] Furthermore, in the outer periphery 20a of the first negative electrode and the outer periphery 20b of the second negative electrode, the negative electrode material 22 contains a negative electrode active material and an inorganic solid electrolyte 70. In the central part 20c of the negative electrode, the negative electrode material 22 contains a negative electrode active material 23, but does not contain the inorganic solid electrolyte 70.

[0096] The content of the inorganic solid electrolyte 70 in the outer periphery 10a of the first positive electrode and the outer periphery 10b of the second positive electrode may be the same or different. Similarly, the content of the solid electrolyte in the outer periphery 20a of the first negative electrode and the outer periphery 20b of the second negative electrode may be the same or different.

[0097] It is desirable that the inorganic solid electrolyte 70 content in the positive electrode 10 be greater in the outer periphery 10a of the first positive electrode than in the outer periphery 10b of the second positive electrode. Since the resistance of the outer periphery 10a of the first positive electrode tends to be higher than that of the outer periphery 10b of the second positive electrode, increasing the inorganic solid electrolyte 70 content in the outer periphery 10a of the first positive electrode increases the ionic conductivity of the outer periphery 10a of the first positive electrode, thereby more effectively reducing current density unevenness.

[0098] Similarly, it is desirable that the content of the inorganic solid electrolyte 70 in the negative electrode 20 be such that the content in the outer periphery 20a of the first negative electrode is greater than that in the outer periphery 20b of the second negative electrode. Since the resistance of the outer periphery 20a of the first negative electrode tends to be higher than that of the outer periphery 20b of the second negative electrode, increasing the content of the inorganic solid electrolyte 70 in the outer periphery 20a of the first negative electrode can increase the ionic conductivity of the outer periphery 20a of the first negative electrode, thereby more effectively reducing current density unevenness.

[0099] In the second embodiment described above, the laminate-type secondary battery 1 is provided with an inorganic solid electrolyte 70 on both the outer periphery 10a of the first positive electrode and the outer periphery 10b of the second positive electrode. This improves the ionic conductivity of the outer periphery 10a and 10b of the positive electrode, where the gel polymer electrolyte 60 tends to increase viscosity and thus resistance, and reduces current density unevenness in the positive electrode 10. As a result, the output characteristics and cycle characteristics of the secondary battery 1 can be improved.

[0100] Furthermore, in this second embodiment, the laminate-type secondary battery 1 is provided with an inorganic solid electrolyte 70 on both the outer periphery 20a of the first negative electrode and the outer periphery 20b of the second negative electrode. This improves the ionic conductivity of the outer periphery 20a and 20b of the negative electrode, where the gel polymer electrolyte 60 tends to increase viscosity and thus resistance, and reduces current density unevenness in the negative electrode 20. As a result, the output characteristics and cycle characteristics of the secondary battery 1 can be improved.

[0101] Furthermore, according to this second embodiment, by increasing the amount of inorganic solid electrolyte 70 in the outer periphery 10a of the first positive electrode compared to the outer periphery 10b of the second positive electrode, the ionic conductivity of the outer periphery 10a of the first positive electrode can be increased, and the current density unevenness of the positive electrode 10 can be reduced more effectively.

[0102] Furthermore, according to this second embodiment, by increasing the amount of inorganic solid electrolyte 70 in the outer periphery 20a of the first negative electrode compared to the outer periphery 20b of the second negative electrode, the ionic conductivity of the outer periphery 20a of the first negative electrode can be increased, and the current density unevenness of the negative electrode 20 can be reduced more effectively.

[0103] (Third embodiment) Next, a third embodiment of this disclosure will be described. Below, only the parts that differ from the above embodiments will be described. In this third embodiment, the configuration of the positive electrode material 12 and the negative electrode material 22 differs from that of the above embodiments.

[0104] In this third embodiment, the positive electrode material 12 contains a positive electrode active material 13 and an inorganic solid electrolyte 70 in the outer periphery 10a of the first positive electrode, the outer periphery 10b of the second positive electrode, and the central part 10c of the positive electrode. In other words, in this third embodiment, the inorganic solid electrolyte 70 is added to the entire positive electrode 10.

[0105] In this third embodiment, the negative electrode material 22 contains a negative electrode active material 23 and an inorganic solid electrolyte 70 in the outer periphery 20a of the first negative electrode, the outer periphery 20b of the second negative electrode, and the central part 20c of the negative electrode. In other words, in this third embodiment, the inorganic solid electrolyte 70 is added to the entire negative electrode 20.

[0106] The content of the inorganic solid electrolyte 70 in the outer periphery 10a of the first positive electrode, the outer periphery 10b of the second positive electrode, and the center 10c of the positive electrode may be the same or different. Similarly, the content of the solid electrolyte in the outer periphery 20a of the first negative electrode, the outer periphery 20b of the second negative electrode, and the center 20c of the negative electrode may be the same or different.

[0107] It is desirable that the content of the inorganic solid electrolyte 70 in the positive electrode 10 be in the order of first positive electrode outer periphery 10a > second positive electrode outer periphery 10b > positive electrode center 10c. The resistance of the first positive electrode outer periphery 10a tends to be higher than that of the second positive electrode outer periphery 10b, and the resistance of the second positive electrode outer periphery 10b tends to be higher than that of the positive electrode center 10c. Therefore, by setting the content of the inorganic solid electrolyte 70 in the positive electrode 10 in the order of first positive electrode outer periphery 10a > second positive electrode outer periphery 10b > positive electrode center 10c, the current density unevenness of the positive electrode 10 can be reduced more effectively.

[0108] It is desirable that the content of the inorganic solid electrolyte 70 in the negative electrode 20 be in the order of first negative electrode outer periphery 20a > second negative electrode outer periphery 20b > negative electrode center 20c. The resistance of the first negative electrode outer periphery 20a tends to be higher than that of the second negative electrode outer periphery 20b, and the resistance of the second negative electrode outer periphery 20b tends to be higher than that of the negative electrode center 20c. Therefore, by setting the content of the inorganic solid electrolyte 70 in the negative electrode 20 in the order of first negative electrode outer periphery 20a > second negative electrode outer periphery 20b > negative electrode center 20c, the current density unevenness of the negative electrode 20 can be reduced more effectively.

[0109] According to the third embodiment described above, in the laminate-type secondary battery 1, an inorganic solid electrolyte 70 is provided in the outer periphery 10a of the first positive electrode, the outer periphery 10b of the second positive electrode, and the central part 10c of the positive electrode. This makes it possible to improve the ionic conductivity of the entire positive electrode 10, and to improve the output characteristics and cycle characteristics of the secondary battery 1.

[0110] Furthermore, according to this third embodiment, in the laminate-type secondary battery 1, an inorganic solid electrolyte 70 is provided in the outer periphery 20a of the first negative electrode, the outer periphery 20b of the second negative electrode, and the central part 20c of the negative electrode. This makes it possible to improve the ionic conductivity of the negative electrode 20 as a whole, and to improve the output characteristics and cycle characteristics of the secondary battery 1.

[0111] (Examples) Next, examples and comparative examples of this disclosure will be described with reference to Figure 9. Examples 1 to 9 and comparative examples 1 to 4 differ in the region where the inorganic solid electrolyte 70 is provided in the positive electrode 10 or negative electrode 20, or in the type of inorganic solid electrolyte 70. In Figure 9, the output characteristics and cycle characteristics are shown as relative values ​​with the value of Comparative Example 1 set to 100%.

[0112] The output performance and cycle characteristics shown in Figure 9 were measured using a charge / discharge device manufactured by Hokuto Denko Co., Ltd. The output characteristics in Figure 9 evaluate the discharge time under the condition of constant current / constant voltage charging at 0.2C to 4.3V in a 25°C environment, followed by constant current discharge to 2.5V at 10C. The cycle characteristics in Figure 9 evaluate the number of cycles at which the discharge capacity becomes 80% or less of the initial discharge capacity, with one cycle defined as a charge / discharge cycle consisting of constant current / constant voltage discharge at 1.0C to 4.3V in a 45°C environment, followed by constant current discharge to 2.5V at 7C.

[0113] In Examples 1-9 and Comparative Examples 1-4 in Figure 9, LiNi is used as the positive electrode active material 13. 0.8 Co 0.1 Mn 0.1 O2 (NCM811) was used, and graphite was used as the negative electrode active material 23. In addition, the gel polymer electrolyte 60 used in Examples 1-9 and Comparative Examples 1-4 contained a vinylidene fluoride copolymer as the polymer, LiPF6 as the lithium salt, and ethylene carbonate as the solvent.

[0114] In Examples 1-7, a sulfide-based solid electrolyte was used as the inorganic solid electrolyte 70. In Examples 1-7, Li6PS5Cl, an argyrodite-type solid electrolyte, was used as the sulfide-based solid electrolyte. In Examples 1-9 and Comparative Examples 1-4, the inorganic solid electrolyte 70 was added at a content of 5% when preparing the slurry of the positive electrode material 12 or the negative electrode material 12.

[0115] In Examples 8 and 9, an oxide-based solid electrolyte was used as the inorganic solid electrolyte 70. In Example 8, the oxide-based solid electrolyte was Li7La3Zr2O, which is a garnet-type solid electrolyte. 12 (LLZ) is used. In Example 9, Li is used as the oxide-based solid electrolyte, which is a pyrochlore-type solid electrolyte. 1.25 La 0.58 Nb2O6F(LLNOF) is used.

[0116] In Comparative Example 1, no inorganic solid electrolyte 70 was used. In Comparative Examples 2 to 4, Li6PS5Cl, a sulfide-based solid electrolyte, was used as the inorganic solid electrolyte 70.

[0117] In the "Addition of Inorganic Solid Electrolyte" column of Figure 9, the parts of the positive electrode 10 and negative electrode 20 where the inorganic solid electrolyte 70 is provided are marked "Present," and the parts where the inorganic solid electrolyte 70 is not provided are left blank.

[0118] In Example 1, an inorganic solid electrolyte 70 (sulfide) is provided on the outer periphery 20a of the first negative electrode. In Example 2, an inorganic solid electrolyte 70 (sulfide) is provided on the outer periphery 20a of the first negative electrode and the outer periphery 20b of the second negative electrode. In Example 3, an inorganic solid electrolyte 70 (sulfide) is provided on the outer periphery 20a of the first negative electrode, the outer periphery 20b of the second negative electrode, and the center 20c of the negative electrode.

[0119] In Example 4, an inorganic solid electrolyte 70 (sulfide) is provided on the outer periphery 10a of the first positive electrode. In Example 5, an inorganic solid electrolyte 70 (sulfide) is provided on the outer periphery 10a of the first positive electrode and the outer periphery 10b of the second positive electrode. In Example 6, an inorganic solid electrolyte 70 (sulfide) is provided on the outer periphery 10a of the first positive electrode, the outer periphery 10b of the second positive electrode, and the center 10c of the positive electrode.

[0120] In Example 7, an inorganic solid electrolyte 70 (sulfide) is provided on the outer periphery 10a of the first positive electrode, the outer periphery 10b of the second positive electrode, the outer periphery 20a of the first negative electrode, and the outer periphery 20b of the second negative electrode. In Examples 8 and 9, an inorganic solid electrolyte 70 (oxide) is provided on the outer periphery 10a of the first positive electrode, the outer periphery 10b of the second positive electrode, the outer periphery 20a of the first negative electrode, and the outer periphery 20b of the second negative electrode.

[0121] Comparative Example 2 has an inorganic solid electrolyte 70 (sulfide) in the center 20c of the negative electrode. Comparative Example 3 has an inorganic solid electrolyte 70 (sulfide) in the center 10c of the positive electrode. Comparative Example 4 has an inorganic solid electrolyte 70 (sulfide) in the center 20c of the negative electrode and the center 10c of the positive electrode.

[0122] As shown in Figure 9, in all of Examples 1 to 9, the output characteristics and cycle characteristics exceeded 100%.

[0123] In Example 1, by providing an inorganic solid electrolyte 70 on the outer periphery 20a of the first negative electrode, the output characteristics and cycle characteristics of the secondary battery 1 exceeded 100%, and the output characteristics and cycle characteristics of the secondary battery 1 were improved compared to Comparative Example 1. This is thought to be a result of the ion transport resistance of the outer periphery 20a of the first negative electrode where the inorganic solid electrolyte 70 is provided decreasing, and the current density unevenness of the negative electrode 20 being reduced.

[0124] In Example 2, by providing an inorganic solid electrolyte 70 on the outer periphery 20a of the first negative electrode and the outer periphery 20b of the second negative electrode, the output characteristics and cycle characteristics of the secondary battery 1 are higher than in Example 1. This is thought to be a result of a decrease in the ion transport resistance of the outer periphery 20a of the first negative electrode and the outer periphery 20b of the second negative electrode, and a reduction in the current density unevenness of the negative electrode 20 compared to Example 1.

[0125] In Example 3, the output characteristics of the secondary battery 1 are higher than in Example 2 because the inorganic solid electrolyte 70 is provided on the outer periphery 20a of the first negative electrode, the outer periphery 20b of the second negative electrode, and the center 20c of the negative electrode. This is thought to be because the ion transport resistance of the entire negative electrode 20 has decreased, resulting in improved output characteristics of the secondary battery 1. On the other hand, in Example 3, the cycle characteristics of the secondary battery 1 are lower than in Example 2. This is thought to be because the improvement in current density uniformity is lower than in Example 2 as a result of the ion transport resistance decreasing throughout the entire negative electrode 20.

[0126] In Example 4, by providing an inorganic solid electrolyte 70 on the outer periphery 10a of the first positive electrode, the output characteristics and cycle characteristics of the secondary battery 1 exceeded 100%, and the output characteristics and cycle characteristics of the secondary battery 1 were improved compared to Comparative Example 1. This is thought to be a result of the ion transport resistance of the outer periphery 10a of the first positive electrode where the inorganic solid electrolyte 70 is provided decreasing, and the current density unevenness of the negative electrode 20 being reduced.

[0127] In Example 5, by providing an inorganic solid electrolyte 70 on the outer periphery 10a of the first positive electrode and the outer periphery 10b of the second positive electrode, the output characteristics and cycle characteristics of the secondary battery 1 are higher than in Example 4. This is thought to be a result of the ion transport resistance of the outer periphery 10a of the first positive electrode and the outer periphery 10b of the second positive electrode being reduced, and the current density unevenness of the negative electrode 20 being reduced compared to Example 4.

[0128] In Example 6, by providing an inorganic solid electrolyte 70 on the outer periphery 10a of the first positive electrode, the outer periphery 10b of the second positive electrode, and the center 10c of the positive electrode, the output characteristics of the secondary battery 1 are higher than in Example 5. This is thought to be because the ion transport resistance of the entire positive electrode 10 has decreased, resulting in improved output characteristics of the secondary battery 1. On the other hand, in Example 6, the cycle characteristics of the secondary battery 1 are lower than in Example 5. This is thought to be because the ion transport resistance of the entire negative electrode 20 has decreased, resulting in a lower degree of improvement in current density uniformity compared to Example 5.

[0129] In Example 7, an inorganic solid electrolyte 70 is provided on the outer periphery 10a of the first positive electrode, the outer periphery 10b of the second positive electrode, the outer periphery 20a of the first negative electrode, and the outer periphery 20b of the second negative electrode. In Example 7, the output characteristics and cycle characteristics are higher than in Example 2, in which the inorganic solid electrolyte 70 is provided on the outer periphery 20a of the first negative electrode and the outer periphery 20b of the second negative electrode. Similarly, in Example 7, the output characteristics and cycle characteristics are higher than in Example 5, in which the inorganic solid electrolyte 70 is provided on the outer periphery 10a of the first positive electrode and the outer periphery 10b of the second positive electrode. In other words, by providing the inorganic solid electrolyte 70 on both the outer periphery 10a and 10b of the positive electrode and the outer periphery 20a and 20b of the negative electrode, it is possible to improve the output characteristics and cycle characteristics compared to cases where the inorganic solid electrolyte 70 is provided only on the outer periphery 10a and 10b of the positive electrode or only on the outer periphery 20a and 20b of the negative electrode.

[0130] Here, we compare embodiments having similar configurations for the positive electrode 10 and the negative electrode 20. Embodiment 4, in which the inorganic solid electrolyte 70 is provided on the positive electrode 10, shows higher output characteristics and cycle characteristics for the secondary battery 1 than Embodiment 1, in which the inorganic solid electrolyte 70 is provided on the negative electrode 20. Similarly, Embodiment 5, in which the inorganic solid electrolyte 70 is provided on the positive electrode 10, shows higher output characteristics and cycle characteristics for the secondary battery 1 than Embodiment 2, in which the inorganic solid electrolyte 70 is provided on the negative electrode 20. Similarly, Embodiment 6, in which the inorganic solid electrolyte 70 is provided on the positive electrode 10, shows higher output characteristics and cycle characteristics for the secondary battery 1 than Embodiment 3, in which the inorganic solid electrolyte 70 is provided on the negative electrode 20. This is thought to be because the interfacial resistance between the electrode and electrolyte is greater on the positive electrode 10 than on the negative electrode 20, resulting in a greater improvement in current density uniformity when the inorganic solid electrolyte 70 is provided on the positive electrode 10 than when the inorganic solid electrolyte 70 is provided on the negative electrode 20.

[0131] Comparing Example 7, which differs only in the type of inorganic solid electrolyte 70, with Examples 8 and 9, Examples 8 and 9, which use oxide-based solid electrolytes, show higher output characteristics and cycle characteristics of the secondary battery 1 than Example 7, which uses sulfide-based solid electrolytes. This is thought to be because oxide-based solid electrolytes can suppress partial decomposition by reacting with the gel polymer electrolyte 60 compared to sulfide-based solid electrolytes, resulting in a greater effect in improving current density uniformity.

[0132] Comparing Example 8 and Example 9, which differ only in the type of oxide-based solid electrolyte, Example 9, which uses a pyrochlore-type solid electrolyte (LLNOF), shows higher output and cycle characteristics for secondary battery 1 than Example 8, which uses a garnet-type solid electrolyte (LLZ). This is thought to be a result of the higher ionic conductivity of the pyrochlore-type solid electrolyte, which enhances the effect of improving current density uniformity.

[0133] Comparative Examples 2-4 showed an output characteristic of 100%. This is likely because the resistance of the outer periphery 20a, 20b of the negative electrode and the outer periphery 10a, 10b of the positive electrode, where the inorganic solid electrolyte 70 was not provided, remained unchanged, and the output characteristic did not improve. Furthermore, the cycle characteristics of Comparative Examples 2-4 were below 100%. This is likely because the reduced resistance of the central part 20c of the negative electrode and the central part 10c of the positive electrode, where the inorganic solid electrolyte 70 was provided, resulted in greater current density unevenness, leading to further degradation of the central parts 20c and 10c of the negative electrode and positive electrode. In particular, Comparative Example 4, where the inorganic solid electrolyte 70 was provided in both the central parts 20c and 10c of the negative electrode, showed a significant decrease in cycle characteristics.

[0134] (Other embodiments) This disclosure is not limited to the embodiments described above, and can be modified in various ways without departing from the spirit of this disclosure. Furthermore, the means disclosed in each of the embodiments described above may be combined as appropriate to the extent that they are feasible.

[0135] For example, in the above embodiment, an example was described in which the active material composite particles of this disclosure were applied to a lithium-ion battery in which the conductive ions are lithium ions, but they may also be applied to secondary batteries with different conductive ions. Specifically, the active material composite particles of this disclosure can be applied to potassium-ion batteries in which potassium ions conduct, sodium-ion batteries in which sodium ions conduct, and the like.

[0136] Furthermore, in the first embodiment described above, an example was described in which an inorganic solid electrolyte 70 is provided on the outer periphery 10a of the first positive electrode and the outer periphery 20a of the first negative electrode, but an example was described in which an inorganic solid electrolyte 70 is not provided on the outer periphery 10b of the second positive electrode and the outer periphery 20b of the second negative electrode. However, it is also possible to configure the device so that an inorganic solid electrolyte 70 is not provided on the outer periphery 10a of the first positive electrode and the outer periphery 20a of the first negative electrode, but is provided on the outer periphery 10b of the second positive electrode and the outer periphery 20b of the second negative electrode.

[0137] Furthermore, although the above embodiments described examples in which the inorganic solid electrolyte 70 is provided on both the positive electrode 10 and the negative electrode 20, it is sufficient if the inorganic solid electrolyte 70 is provided on at least one of the positive electrode 10 or the negative electrode 20. When the inorganic solid electrolyte 70 is provided on either the positive electrode 10 or the negative electrode 20, it is desirable to provide the inorganic solid electrolyte 70 on the positive electrode 10, which has a greater interfacial resistance between the electrode and the electrolyte.

[0138] Furthermore, although the above embodiments described a configuration in which a plurality of separator bends 30b are formed on a zigzag-folded separator 30, it is sufficient for at least one separator bend 30b to be formed.

[0139] The characteristics of the secondary battery disclosed herein are as follows: (Item 1) The device comprises electrodes (10, 20), a separator (30), a gel polymer electrolyte (60), and an outer casing (50) that houses the electrodes, the separator, and the gel polymer electrolyte. The electrode comprises a positive electrode (10) containing a positive electrode active material (13) and a negative electrode (20) containing a negative electrode active material (23). The positive electrode and the negative electrode are stacked alternately with respect to the separator. The separator has a first portion (30a) that sandwiches at least one of the electrodes, the positive electrode and the negative electrode, and a second portion (30b) that is bent to connect the first portions of the stacked separators. The electrode has a bent outer peripheral portion (10a, 20a) that includes a bent end portion (10d, 20d) positioned opposite the second portion (30b) of the separator, A secondary battery in which an inorganic solid electrolyte (70) is contained in the outer circumference of the bent side of at least one of the electrodes, either the positive electrode or the negative electrode. (Item 2) The secondary battery according to item 1, wherein the bent outer periphery includes the bent end and has a length of 1 / 3 or less of the length of the electrode in the direction connecting the bent end and the opposite end (10e, 20e) on the side farther from the bent portion. (Item 3) The electrode has an outer peripheral portion (10b, 20b) opposite to the end opposite to the bent portion, The secondary battery according to item 1 or 2, wherein the outer periphery on the opposite side contains at least one of the positive electrode active material and the negative electrode active material, and the inorganic solid electrolyte. (Item 4) The secondary battery according to item 3, wherein the opposite outer circumference includes the opposite end and has a length of 1 / 3 or less of the length of the electrode in the direction connecting the bent end and the opposite end. (Item 5) The secondary battery according to item 4, wherein the amount of the inorganic solid electrolyte contained in the outer peripheral portion on the bending side and the outer peripheral portion on the opposite side is in the order of outer peripheral portion on the bending side > outer peripheral portion on the opposite side. (Item 6) The electrode is provided with a central portion (10c, 20c) sandwiched between the bent outer circumference and the opposite outer circumference. The secondary battery according to any one of items 3 to 5, wherein the central part contains at least one of the positive electrode active material and the negative electrode active material, and the inorganic solid electrolyte. (Item 7) The secondary battery according to item 6, wherein the content of the inorganic solid electrolyte contained in the bent outer periphery, the opposite outer periphery, and the central part is in the order of bent outer periphery > opposite outer periphery > central part. (Item 8) The electrode containing the inorganic solid electrolyte in the outer circumference of the bent side is the positive electrode, as described in any one of items 1 to 7 of the secondary battery. (Item 9) The electrode containing the inorganic solid electrolyte in the outer circumference of the bent side is the positive electrode and the negative electrode, as described in any one of items 1 to 7 of the secondary battery. (Item 10) The secondary battery described in item 9, wherein the amount of the inorganic solid electrolyte contained in the positive electrode and the negative electrode is in the order of positive electrode > negative electrode. (Item 11) The secondary battery according to any one of items 1 to 10, wherein the inorganic solid electrolyte is an oxide-based solid electrolyte. (Item 12) The secondary battery according to item 11, wherein the oxide-based solid electrolyte is a pyrochlore-type solid electrolyte having a pyrochlore structure. (Item 13) The pyrochlore-type solid electrolyte has the composition formula Aa 2-α Ab (1+α) / 3 B2O 7-β X γ The secondary battery according to item 12, wherein Aa is an alkali metal, Ab contains at least a lanthanide, B is a cation different from Aa and Ab, X is an anion that can be replaced by an O atom constituting the pyrochlore-type solid electrolyte, and in the composition formula, α is in the range of 0.6 < α < 2.0, β is in the range of 0 < β ≤ 1, γ is in the range of 0 < γ ≤ 1, and includes a defect structure. [Explanation of Symbols]

[0140] 10 positive electrode 10a Outer circumference of the first positive electrode (outer circumference on the bent side) 10b Second positive electrode outer circumference (opposite outer circumference) 10c Center of positive electrode (center) 10d 1st positive end (bent end) 10e Second positive terminal (opposite end) 13 Cathode active material 20 negative electrode 20a Outer circumference of the first negative electrode (outer circumference on the bent side) 20b Second negative electrode outer periphery (opposite outer periphery) 20c Negative electrode center (center) 20d 1st negative end (bent end) 20e Second negative pole end (opposite end) 23 Negative electrode active material 30 Separators 30a Flat part (1st part) 30b Separator bend (second part) 60 Gel polymer electrolyte 70 Inorganic solid electrolyte

Claims

1. The device comprises electrodes (10, 20), a separator (30), a gel polymer electrolyte (60), and an outer casing (50) that houses the electrodes, the separator, and the gel polymer electrolyte. The electrode comprises a positive electrode (10) containing a positive electrode active material (13) and a negative electrode (20) containing a negative electrode active material (23). The positive electrode and the negative electrode are stacked alternately with respect to the separator. The separator has a first portion (30a) that sandwiches at least one of the electrodes, the positive electrode and the negative electrode, and a second portion (30b) that is bent to connect the first portions of the stacked separators. The electrode has a bent outer peripheral portion (10a, 20a) that includes a bent end portion (10d, 20d) that is positioned opposite the second portion (30b) of the separator, A secondary battery in which an inorganic solid electrolyte (70) is contained in the outer circumference of the bent side of at least one of the electrodes, either the positive electrode or the negative electrode.

2. The secondary battery according to claim 1, wherein the bent outer periphery includes the bent end and has a length of 1 / 3 or less of the length of the electrode in the direction connecting the bent end and the opposite end (10e, 20e) on the side farther from the second portion.

3. The electrode has an outer peripheral portion (10b, 20b) opposite to the end opposite to the second portion, The secondary battery according to claim 1, wherein the opposite outer periphery contains at least one of the positive electrode active material and the negative electrode active material and the inorganic solid electrolyte.

4. The secondary battery according to claim 3, wherein the opposite outer circumference includes the opposite end and has a length of 1 / 3 or less of the length of the electrode in the direction connecting the bent end and the opposite end.

5. The secondary battery according to claim 4, wherein the amount of the inorganic solid electrolyte contained in the outer peripheral portion on the bent side and the outer peripheral portion on the opposite side is in the order of outer peripheral portion on the bent side > outer peripheral portion on the opposite side.

6. The electrode is provided with a central portion (10c, 20c) sandwiched between the bent outer circumference and the opposite outer circumference. The secondary battery according to claim 3, wherein at least one of the positive electrode active material and the negative electrode active material and the inorganic solid electrolyte are added to the central part.

7. The secondary battery according to claim 6, wherein the amount of the inorganic solid electrolyte contained in the bent outer periphery, the opposite outer periphery, and the central part is in the order of bent outer periphery > opposite outer periphery > central part.

8. The secondary battery according to claim 1, wherein the electrode containing the inorganic solid electrolyte in the outer peripheral portion of the bent side is the positive electrode.

9. The secondary battery according to claim 1, wherein the electrode containing the inorganic solid electrolyte in the outer peripheral portion of the bent side is the positive electrode and the negative electrode.

10. The secondary battery according to claim 9, wherein the amount of the inorganic solid electrolyte contained in the positive electrode and the negative electrode is in the order of positive electrode > negative electrode.

11. The secondary battery according to claim 1, wherein the inorganic solid electrolyte is an oxide-based solid electrolyte.

12. The secondary battery according to claim 11, wherein the oxide-based solid electrolyte is a pyrochlore-type solid electrolyte having a pyrochlore structure.

13. The pyrochlore-type solid electrolyte has the composition formula Aa ２－α Ab （１＋α）／３ B ２ O ７－β X γ The secondary battery according to claim 12, wherein Aa is an alkali metal, Ab contains at least a lanthanide, B is a cation different from Aa and Ab, X is an anion that can be replaced with an O atom constituting the pyrochlore-type solid electrolyte, and in the composition formula, α is in the range of 0.6 < α < 2.0, β is in the range of 0 < β ≤ 1, γ is in the range of 0 < γ ≤ 1, and includes a defect structure.

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