Electrode for secondary battery

Abstract

[Problem] To provide a means capable of preventing the loss of solid electrolyte from a solid electrolyte layer and preventing the occurrence of a short circuit between a positive electrode and a negative electrode. [Solution] An electrode for a secondary battery is provided with: a current collector foil 11; an electrode active material layer 12 arranged on a surface of the collector foil 11 and containing electrode active material; a solid electrolyte layer 13 containing solid electrolyte, covering the electrode active material layer 12, and having an end part in contact with the collector foil 11; and a protection part 14 arranged at a part where the end part and the current collector foil 11 are in contact with each other, and having elasticity. A cross section of the protection part in the stack direction has a tapered shape that widens toward the current collector foil, and an outer peripheral end of the protection part coincides with an outer peripheral end of the current collector foil in a plan view.

Description

Electrodes for secondary batteries

[0001] The present invention relates to an electrode for a secondary battery.

[0002] In battery technology, ensuring insulation between the positive and negative electrodes is one of the most important challenges in improving the durability and life of batteries. To solve this problem, Japanese Patent Application Laid-Open No. 2021-150204 proposes covering each of the positive and negative active material layers with a solid electrolyte to prevent the active material from falling off the active material layers, and fixing the positive and negative current collectors to the same size as the solid electrolyte layer to prevent the positive and negative current collectors from coming into close proximity and prevent short circuits.

[0003] However, when manufacturing the battery described in JP 2021-150204 A, the solid electrolyte layer is cut together with the current collector in the cutting process, so the solid electrolyte, which is brittle as a molded body, may crack and break off during cutting. If the broken solid electrolyte adheres to the electrode, the surface pressure at the adhesion part increases, and lithium deposition may concentrate, causing a short circuit.

[0004] Therefore, the present invention aims to solve the above problems and to provide a means that can prevent the solid electrolyte from falling off from the solid electrolyte layer and suppress the occurrence of short circuits between the positive electrode and the negative electrode.

[0005] The electrode for a secondary battery according to the present invention comprises a current collecting foil, an electrode active material layer containing an electrode active material formed on the surface of the current collecting foil, a solid electrolyte layer containing a solid electrolyte, covering the electrode active material layer and having an edge in contact with the current collecting foil, and an elastic protective part disposed at a location where the edge contacts the current collecting foil. The electrode is characterized in that the cross section of the protective part in the stacking direction has a sloping shape that widens toward the current collecting foil, and the outer peripheral edge of the protective part coincides with the outer peripheral edge of the current collecting foil in plan view.

[0006] Fig. 1 is a schematic cross-sectional view of a main part illustrating the configuration of an electrode according to a first embodiment. Fig. 2 is a plan view of the electrode shown in Fig. 1. Fig. 3 is a plan view of an electrode according to a second embodiment. Fig. 4 is a cross-sectional view of an electrode according to a third embodiment. Fig. 5 is a cross-sectional view of an electrode according to a fourth embodiment. Fig. 6(a) is a plan view of an electrode sheet produced in an electrode sheet production step of a method for producing an electrode according to one embodiment. Fig. 6(b) is a cross-sectional view of the electrode sheet shown in Fig. 6(a).

[0007] One aspect of the present invention is an electrode for a secondary battery, comprising: a current collector foil; an electrode active material layer formed on a surface of the current collector foil and containing an electrode active material; a solid electrolyte layer containing a solid electrolyte, covering the electrode active material layer and having an edge in contact with the current collector foil; and an elastic protective part disposed at a portion where the edge and the current collector foil contact, wherein a cross section of the protective part in the stacking direction has a sloping shape that widens toward the current collector foil, and an outer peripheral edge of the protective part coincides with an outer peripheral edge of the current collector foil in a plan view. According to the present invention, it is possible to prevent the solid electrolyte from falling off from the solid electrolyte layer and to suppress the occurrence of a short circuit between a positive electrode and a negative electrode.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicate explanations will be omitted. Furthermore, the dimensional proportions in the drawings are exaggerated for the convenience of explanation and may differ from the actual proportions.

[0009] First Embodiment An electrode 10 according to a first embodiment of the present invention will now be described.

[0010] Fig. 1 is a schematic cross-sectional view illustrating the configuration of an electrode 10 according to this embodiment. Fig. 2 is a plan view of the electrode 10 shown in Fig. 1.

[0011] 1 and 2 , electrode 10 has electrode active material layers 12 disposed on both sides of current collector foil 11, and solid electrolyte layer 13 covering electrode active material layer 12. Current collector foil 11, electrode active material layer 12, and solid electrolyte layer 13 all have a rectangular shape when viewed from above. Here, electrode active material layer 12, solid electrolyte layer 13, and protective portion 14 are disposed on both sides of current collector foil 11, respectively.

[0012] In this embodiment, an end of the solid electrolyte layer 13 contacts the current collector foil 11. An elastic protective portion 14 is disposed at the end of the solid electrolyte layer 13. The cross section of the protective portion 14 in the stacking direction has an inclined shape that widens toward the current collector foil 11, and in plan view, the outer circumferential edge of the protective portion 14 coincides with the outer circumferential edge of the current collector foil 11. The electrode 10 according to this embodiment prevents the solid electrolyte from being removed from the solid electrolyte layer 13, thereby suppressing the occurrence of short circuits between the positive and negative electrodes. Furthermore, when cutting the electrode in the battery manufacturing process, the cutting blade does not come into contact with the solid electrolyte layer 13, which also suppresses the removal of the solid electrolyte from the solid electrolyte layer 13.

[0013] In addition, protective portion 14 has an inclined shape that widens toward current collector foil 11. This makes it possible to minimize the amount of solid electrolyte that is lost even if a cutting blade hits protective portion 14 during the battery manufacturing process. Furthermore, because the outer peripheral edge of protective portion 14 and the outer peripheral edge of current collector foil 11 are aligned in a plan view, it is possible to effectively prevent the positive and negative current collector foils from coming close to each other in a single cell and causing a short circuit.

[0014] A secondary battery employing the secondary battery electrode according to the present embodiment may be a so-called stacked-type battery, in which a power generating element composed of multiple stacked cell layers is housed within the battery, sealed in a laminate film as a battery exterior material. The stacked-type battery allows for a compact and high-capacity battery. However, the cell layers housed in a secondary battery employing the electrode according to the present embodiment do not necessarily have to be multiple layers; they may be single layers. Furthermore, the appearance of the secondary battery and the internal electrical connection state (electrode structure) are not particularly limited. The appearance of the secondary battery may be, for example, a flattened rectangular shape, or a circular or elliptical shape. Alternatively, the secondary battery may be a cylindrical shape in which a single or multiple cell layers are wound and housed. Furthermore, the electrode structure of the secondary battery may be either a so-called non-bipolar type (internal parallel connection type) or a bipolar type (internal series connection type). In other words, aspects other than the configuration of the electrode 10 described below are not particularly limited, regardless of whether they are publicly known or not. The electrode 10 according to this embodiment may be a positive electrode or a negative electrode in a secondary battery.

[0015] Next, the components constituting the electrode according to this embodiment will be described.

[0016] [Current Collector Foil] Generally known materials are used as the material for the current collector foil 11. For example, metals and conductive resins are used.

[0017] Specifically, metals used as constituent materials of the current collector foil include aluminum, nickel, iron, stainless steel, titanium, platinum, gold, and copper. In addition to these, a clad material of nickel and aluminum, or a clad material of copper and aluminum may also be used. Furthermore, the foil may be one in which the surface of a metal is coated with aluminum.

[0018] The conductive resin used as the constituent material of the current collector foil may be a resin obtained by adding a conductive filler to a non-conductive polymer material as required.

[0019] In particular, examples of non-conductive polymeric materials include polyethylene (PE; high density polyethylene (HDPE) or low density polyethylene (LDPE)), polypropylene (PP), polyethylene terephthalate (PET), polyethernitrile (PEN), polyimide (PI), polyamideimide (PAI), polyamide (PA), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylonitrile (PAN), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyvinyl chloride (PVC), polyvinylidene fluoride (PVdF), and polystyrene (PS).

[0020] The thickness of the current collector foil varies depending on the intended electrode configuration, but is preferably within the range of 5 to 50 μm, and particularly preferably within the range of 8 to 20 μm.

[0021] [Positive Electrode Active Material Layer] When the electrode active material layer 12 is a positive electrode active material layer, a commonly known material is used as the material constituting the positive electrode active material layer. Examples of materials constituting the positive electrode active material layer include sulfur-containing materials (elemental sulfur or sulfur compounds) and sulfur-free materials (metal compounds, etc.). Examples of sulfur-containing materials include particles of elemental sulfur (S), organic sulfur compounds, or inorganic sulfur compounds. In particular, the sulfur-containing material may be a substance that can release lithium ions during charging and absorb lithium ions during discharging by utilizing the oxidation-reduction reaction of sulfur.

[0022] Examples of organic sulfur compounds include disulfide compounds, sulfur-modified polyacrylonitriles typified by the compounds described in WO 2010 / 044437, sulfur-modified polyisoprene, rubeanic acid (dithiooxamide), polycarbon sulfide, etc. Among these, disulfide compounds, sulfur-modified polyacrylonitriles, and rubeanic acid are preferred, and sulfur-modified polyacrylonitriles are particularly preferred.

[0023] As the disulfide compound, a dithiobiurea derivative, a compound having a thiourea group, a thioisocyanate group, or a thioamide group is more preferred.

[0024] Here, sulfur-modified polyacrylonitrile is a modified polyacrylonitrile containing sulfur atoms, obtained by mixing sulfur powder with polyacrylonitrile and heating the mixture under an inert gas or under reduced pressure. Its estimated structure is, for example, as shown in Chem. Mater. 2011, 23, 5024-5028, in which polyacrylonitrile is ring-closed to form a polycyclic ring, and at least a part of S is bonded to C. The compound described in this document has a Raman spectrum of 1330 cm －１ and 1560 cm －１ There is a strong peak signal near 307 cm －１ , 379 cm －１ , 472 cm －１ , 929 cm －１ There is a peak nearby.

[0025] On the other hand, inorganic sulfur compounds are preferred because of their excellent stability. Specifically, sulfur element (S), S-carbon composite, TiS ２ , TiS ３ , TiS ４ , NiS, NiS ２ , CuS, FeS ２ , Li ２ S, MoS ２ , MoS ３ Among them, S, S-carbon composite, TiS ２ , TiS ３ , TiS ４ , FeS ２ and MoS ２ are preferred, and elemental sulfur (S), S-carbon composite, TiS ２ and FeS ２is more preferred, and elemental sulfur (S) is particularly preferred. Here, the S-carbon composite refers to a composite containing sulfur powder and a carbon material, which are formed by subjecting them to heat treatment or mechanical mixing. More specifically, it refers to a state in which sulfur is distributed on the surface or in the pores of the carbon material, a state in which sulfur and the carbon material are uniformly dispersed at the nano-level and aggregated to form particles, a state in which the carbon material is distributed on the surface or inside of fine sulfur powder, or a state in which two or more of these states are combined.

[0026] Further, sulfur-free materials include metal oxides, particularly lithium metal composite oxides. Examples of lithium metal composite oxides include LiCoO ２ , LiMnO ２ , LiNiO ２ , LiVO ２ , or Li(Ni—Mn—Co)O ２ Layered rock salt compounds such as LiMn ２ O ４ , or LiNi ０．５ Mn １．５ O ４ spinel-type compounds such as LiFePO ４ , or LiMnPO ４ Olivine type compounds such as Li ２ FeSiO ４ , or Li ２ MnSiO ４ Examples of lithium metal composite oxides other than those mentioned above include Si-containing compounds such as Li ４ Ti ５ O １２ Examples include:

[0027] In some cases, two or more positive electrode active materials may be used in combination. Of course, positive electrode active materials other than those mentioned above may also be used.

[0028] The shape of the positive electrode active material may be, for example, particulate (spherical, fibrous) or thin film. When the positive electrode active material is particulate, its average particle size (D50) is, for example, preferably in the range of 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, even more preferably in the range of 100 nm to 20 μm, and particularly preferably in the range of 1 to 20 μm. In this specification, the average particle size (D50) of the active material can be measured by a laser diffraction scattering method.

[0029] The content of the positive electrode active material in the positive electrode active material layer is not particularly limited, but is preferably within the range of 40 to 99 mass %, and more preferably within the range of 50 to 90 mass %, for example.

[0030] The positive electrode active material layer may contain a solid electrolyte in addition to the positive electrode active material. Specific solid electrolytes to be contained in the positive electrode active material layer can be selected from the same solid electrolytes as those that are components of the solid electrolyte layer described below. By including a solid electrolyte in the positive electrode active material layer, the ionic conductivity of the positive electrode active material layer can be improved. Examples of solid electrolytes include sulfide solid electrolytes and oxide solid electrolytes, with sulfide solid electrolytes being preferred.

[0031] Examples of sulfide solid electrolytes include LiI-Li ２ S-SiS ２ , LiI-Li ２ S-P ２ O ５ , LiI-Li ３ P.O. ４ -P ２ S ５ , Li ２ S-P ２ S ５ , LiI-Li ３ P.S. ４ , LiI-LiBr-Li ３ P.S. ４ , Li ３ P.S. ４ , Li ２ S-P ２ S ５ -LiCl, Li ２ S-P ２ S５ - LiBr, Li ２ S-P ２ S ５ -Li ２ O, Li ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ S-SiS ２ , Li ２ S-SiS ２ - LiI, Li ２ S-SiS ２ - LiBr, Li ２ S-SiS ２ -LiCl, Li ２ S-SiS ２ -B ２ S ３ - LiI, Li ２ S-SiS ２ -P ２ S ５ - LiI, Li ２ S-B ２ S ３ , Li ２ S-P ２ S ５ -Z ｍ S ｎ (where m and n are positive numbers, and Z is Ge, Zn, or Ga), Li ２ S-GeS ２ , Li ２ S-SiS ２ -Li ３ P.O. ４ , Li ２ S-SiS ２ -Li ｘ MO ｙ (where x and y are positive numbers, and M is any of P, Si, Ge, B, Al, Ga, and In). ２ S-P ２ S ５ " is written by Li ２ S and P ２ S ５ The same applies to other descriptions.

[0032] The sulfide solid electrolyte is, for example, Li３ P.S. ４ It may have a Li framework. ４ P ２ S ７ It may have a Li framework. ４ P ２ S ６ It may have a Li skeleton. ３ P.S. ４ Examples of sulfide solid electrolytes having a skeleton include LiI-Li ３ P.S. ４ , LiI-LiBr-Li ３ P.S. ４ , Li ３ P.S. ４ In addition, Li ４ P ２ S ７ Examples of the sulfide solid electrolyte having a skeleton include a Li-P-S solid electrolyte called LPS (for example, Li ７ P ３ S １１ ) can be mentioned. In addition, examples of sulfide solid electrolytes include Li （４－ｘ） Ge （１－ｘ） P ｘ S ４ (x satisfies 0<x<1), etc. may be used. Among them, the sulfide solid electrolyte is preferably a sulfide solid electrolyte containing P element, and the sulfide solid electrolyte is preferably a sulfide solid electrolyte containing Li ２ S-P ２ S ５ It is more preferable that the sulfide solid electrolyte is a material mainly composed of: Furthermore, the sulfide solid electrolyte may contain a halogen (F, Cl, Br, I).

[0033] In addition, the sulfide solid electrolyte is Li ２ S-P ２ S ５ In the case of the system, Li ２ S and P ２ S ５ The ratio is the molar ratio of Li ２ S:P ２ S ５ = 50:50 to 100:0, and among these, Li ２ S:P ２ S ５It is preferable that the ratio is 70:30 to 80:20.

[0034] The sulfide solid electrolyte may be sulfide glass, crystallized sulfide glass, or a crystalline material obtained by a solid-phase method. The sulfide glass can be obtained, for example, by mechanical milling (ball mill, etc.) a raw material composition. The crystallized sulfide glass can be obtained, for example, by heat treating the sulfide glass at a temperature equal to or higher than the crystallization temperature. The ionic conductivity (e.g., Li ion conductivity) of the sulfide solid electrolyte at room temperature (25°C) is, for example, 1 × 10 －５ S / cm or more, and preferably 1×10 －４ The ionic conductivity of the solid electrolyte can be measured by an AC impedance method.

[0035] Examples of oxide solid electrolytes include compounds having a NASICON structure. An example of a compound having a NASICON structure is a compound represented by the general formula Li １＋ｘ Al ｘ Ge ２－ｘ (P.O. ４ ) ３ (0≦x≦2) (LAGP), a compound represented by the general formula Li １＋ｘ Al ｘ Ti ２－ｘ (PO4) ３ (0≦x≦2) (LATP) and the like. Another example of the oxide solid electrolyte is LiLaTiO (for example, Li ０．３４ La ０．５１ TiO ３ ), LiPON (e.g., Li ２．９ P.O. ３．３ N ０．４６ ), LiLaZrO (e.g., Li ７ La ３ Zr ２ O １２ ) etc.

[0036] Examples of the shape of the solid electrolyte include particulate shapes such as spherical and oval spheres, and thin film shapes. When the solid electrolyte is particulate, its average particle size (D50) is not particularly limited, but is preferably 40 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. On the other hand, the average particle size (D50) is preferably 0.01 μm or more, and more preferably 0.1 μm or more.

[0037] The content of the solid electrolyte in the positive electrode active material layer is, for example, preferably in the range of 1 to 60 mass %, and more preferably in the range of 10 to 50 mass %.

[0038] The positive electrode active material layer may further contain at least one of a conductive additive and a binder in addition to the above-mentioned positive electrode active material and solid electrolyte.

[0039] Examples of conductive additives include, but are not limited to, metals such as aluminum, stainless steel (SUS), silver, gold, copper, and titanium, alloys or metal oxides containing these metals; carbon fibers (specifically, vapor-grown carbon fibers (VGCF), polyacrylonitrile-based carbon fibers, pitch-based carbon fibers, rayon-based carbon fibers, activated carbon fibers, etc.), carbon nanotubes (CNT), and carbon black (specifically, acetylene black, Ketjenblack (registered trademark), furnace black, channel black, thermal lamp black, etc.).

[0040] The material used as the binder is not particularly limited, and any known material in the art may be used as long as it functions as a binder applicable to electrodes for all-solid-state batteries. Examples of binders include polyvinylidene fluoride (PVDF), styrene-butadiene copolymer rubber (SBR), and polyimide.

[0041] The positive electrode active material layer may further contain additives such as a filler, a coating agent, a dispersant, and an ion-conductive auxiliary in addition to the above-mentioned positive electrode active material, solid electrolyte, binder, and conductive auxiliary.

[0042] The thickness of the positive electrode active material layer varies depending on the intended electrode configuration, but is preferably within the range of, for example, 10 to 500 μm.

[0043] [Negative Electrode Active Material Layer] When the electrode active material layer 12 is a negative electrode active material layer, a generally known material is used as the material for the negative electrode active material layer. The material for the negative electrode active material layer is not particularly limited, but examples thereof include a carbon material, a metal oxide, an elemental metal, a silicon material, a tin material, and a lithium (Li)-containing material.

[0044] Examples of carbon materials include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon.

[0045] As the metal oxide, for example, Nb ２ O ５ , or Li ４ Ti ５ O １２ etc.

[0046] Furthermore, a silicon material or a tin material may be used as a material constituting the negative electrode active material layer. Here, silicon and tin belong to Group 14 elements, and it is known that when they are used as materials for the negative electrode active material of a secondary battery, they are elements that can greatly improve the capacity. These simple substances can absorb and release a large number of charge carriers (lithium ions, etc.) per unit volume (mass), and therefore can be materials that can realize a high-capacity negative electrode active material. Here, it is preferable to use Si simple substance as the silicon material. Similarly, SiO disproportionated into two phases, a Si phase and a silicon oxide phase, can be used. ｘ It is also preferable to use silicon oxides such as (0.3≦x≦1.6). In this case, the range of x is more preferably 0.5≦x≦1.5, and even more preferably 0.7≦x≦1.2. Furthermore, an alloy containing silicon may be used as the silicon material. On the other hand, examples of tin materials include simple Sn, tin alloys (Cu—Sn alloys, Co—Sn alloys), amorphous tin oxides, and tin silicon oxides. Of these, examples of amorphous tin oxides include SnB ０．４ P０．６ O ３．１ Examples of tin silicon oxide include SnSiO ３ Examples include:

[0047] The lithium-containing material is not particularly limited as long as it is an active material containing lithium, and in particular, lithium-containing alloys can be mentioned. Examples of lithium-containing alloys include alloys of Li and at least one of In, Al, Si, and Sn. Furthermore, in some cases, the negative electrode active material can be formed by combining any two or more of the above-mentioned constituent materials. Of course, negative electrode active material materials other than those mentioned above can also be used. In addition, in terms of high capacity, it is preferable to use metallic lithium, a silicon material, a tin material, or a combination thereof as the negative electrode active material, and it is particularly preferable to use metallic lithium.

[0048] On the other hand, the shape of the negative electrode active material may be, for example, particulate (spherical, fibrous), thin film, etc. In particular, when the negative electrode active material is particulate, its average particle size (D50) is, for example, preferably in the range of 1 nm to 100 μm, more preferably in the range of 10 nm to 50 μm, even more preferably in the range of 100 nm to 20 μm, and particularly preferably in the range of 1 to 20 μm. The average particle size (D50) of the negative electrode active material can be measured by a laser diffraction scattering method.

[0049] Like the positive electrode active material layer, the negative electrode active material layer may also further include at least one of a solid electrolyte, a conductive additive, and a binder. Furthermore, it may also include additives such as a filler, a coating agent, a dispersant, and an ion-conductive additive. Note that, when the negative electrode active material layer is formed from a metal foil that is alloyed with lithium, a solid electrolyte or the like does not need to be mixed. The specific forms of the solid electrolyte, conductive additive, and binder that can be contained in the negative electrode active material layer are the same as those described above, and therefore, detailed description thereof will be omitted here.

[0050] The thickness of the negative electrode active material layer varies depending on the intended electrode configuration, but is preferably within the range of, for example, 10 to 500 μm.

[0051] [Solid Electrolyte Layer] The solid electrolyte layer 13 included in the electrode 10 according to this embodiment contains a solid electrolyte as a main component, and is a layer that covers the above-described electrode active material layer 12. The specific form of the solid electrolyte contained in the solid electrolyte layer 13 is the same as that described above, and therefore a detailed description thereof will be omitted here.

[0052] The content of the solid electrolyte in the solid electrolyte layer 13 is, for example, preferably in the range of 10 to 100 mass %, more preferably in the range of 50 to 100 mass %, and even more preferably in the range of 90 to 100 mass %.

[0053] The solid electrolyte layer 13 may further contain a binder in addition to the above-described solid electrolyte. The specific form of the binder that can be contained in the solid electrolyte layer 13 is the same as that described above, and therefore detailed description thereof will be omitted here.

[0054] The thickness of the solid electrolyte layer 13 varies depending on the intended configuration of the electrode 10, but is preferably within the range of 0.5 to 100 μm, for example.

[0055] [Protective Part] The protective part 14 is an elastic component disposed at a location where the end of the solid electrolyte layer 13 and the current collector foil 11 come into contact. The protective part 14 is preferably elastic and made of a viscoelastic material so that the protective part does not crack and break off when the cutting blade comes into contact with the protective part when the current collector foil is cut during the battery manufacturing process. Furthermore, the protective part 14 is preferably made of a material that does not react with the solid electrolyte and exhibits electrical insulation properties so that lithium deposition does not concentrate when the protective part 14 breaks off and adheres to the electrode. Particularly preferred materials for the protective part 14 are resin or rubber, and examples include styrene-butadiene rubber (SBR).

[0056] In this embodiment, the height of protective portion 14 from current collector foil 11 (the length in the stacking direction) is set to be smaller than the thickness of solid electrolyte layer 13. This configuration has the advantage that when electrode 10 is stacked with other electrodes to form a battery, the influence of protective portion 14 on the stacked structure of the electrodes is minimized, and a decrease in battery performance can be prevented.

[0057] Furthermore, in this embodiment, the protective portions 14 are arranged on two opposing sides of the rectangular shape of the solid electrolyte layer 13. In this way, an electrode having a solid electrolyte layer 13 with a rectangular shape when viewed in plan can be manufactured easily and with high productivity, for example, by using a continuous manufacturing method as described below. Furthermore, if the protective portions 14 are arranged on at least two opposing sides of the rectangular shape of the solid electrolyte layer 13, when manufacturing an electrode by, for example, a manufacturing method as described below, cutting the solid electrolyte layer 13 with a cutting blade at a position corresponding to these two sides can be prevented from coming into contact with the solid electrolyte layer 13, resulting in the loss of solid electrolyte and a short circuit between the positive electrode and the negative electrode. While the above-described effects can be achieved by arranging the protective portions on two opposing sides of the rectangular shape of the solid electrolyte layer 13, they may be arranged on three sides including these two sides, or on four sides.

[0058] Second Embodiment An electrode 10 according to a second embodiment will be described below. Note that the same elements as those in the first embodiment are given the same reference numerals, and the description thereof will be omitted.

[0059] 3 is a plan view of the electrode 10 according to this embodiment. As shown in the figure, when the electrode 10 according to this embodiment is viewed in plan, the protective portions 14 are also disposed at the four corners of the rectangular shape of the solid electrolyte layer 13. The outer peripheral edges of the protective portions 14 corresponding to these corners have an R-shape. As a result, the surfaces of the current collector foil 11 corresponding to these corners are exposed.

[0060] With the above-described configuration, local force is not applied to the corners when the electrodes are cut, and loss of the solid electrolyte due to cracks in the solid electrolyte layer 13 or the like is suppressed, thereby preventing the occurrence of a short circuit between the positive electrode and the negative electrode.

[0061] Third Embodiment An electrode 10 according to a third embodiment will be described below. Elements similar to those in the first embodiment are designated by the same reference numerals, and descriptions thereof will be omitted.

[0062] 4 is a cross-sectional view of the electrode 10 according to this embodiment. As shown in the figure, in the electrode 10 of this embodiment, the inclination angle of the protective portion 14 arranged on one surface of the current collector foil 11 is different from the inclination angle of the protective portion 14 arranged at an opposing position on the other surface of the current collector foil 11.

[0063] The above-described configuration can improve the yield rate during electrode production.

[0064] Fourth Embodiment An electrode 10 according to a fourth embodiment will be described below. Elements similar to those in the first embodiment are given the same reference numerals, and descriptions thereof will be omitted.

[0065] 5 is a cross-sectional view of the electrode 10 according to this embodiment. As shown in the figure, in the electrode 10 according to this embodiment, the cross sections in the stacking direction of the outer periphery of the electrode active material layer 12 and the outer periphery of the solid electrolyte layer 13 have an inclined shape that widens toward the current collector foil 11.

[0066] The above-described configuration can prevent chipping or cracking of the end portion of the electrode 10. Furthermore, it becomes easier to apply paste for forming the electrode active material layer 12 and the solid electrolyte layer 13 during the manufacture of the electrode.

[0067] [Electrode Manufacturing Method] An example of a manufacturing method for the electrode 10 according to one embodiment of the present invention will be described below. The electrode 10 can be manufactured, for example, by a manufacturing method including forming an electrode active material layer, a solid electrolyte layer, and a protective portion on the surface of a current collector foil to produce an electrode sheet in which electrodes are continuously arranged (electrode sheet manufacturing step), and cutting the electrode sheet between adjacent protective portions (electrode sheet cutting step). This manufacturing method allows electrodes to be manufactured simply and with high productivity.

[0068] [Electrode Sheet Fabrication Process] First, electrode active material layers 12 are continuously formed on both sides of a long current collector foil 11 at predetermined intervals. For example, a paste-like paint prepared by kneading an electrode active material and other materials together with a predetermined solvent is applied to the surface of the current collector foil 11 using a coating device or the like. At this time, a heat pressing treatment may be performed using a roll press or the like as necessary. At this time, each electrode active material layer 12 is formed in contact with the current collector foil 11 and in an area narrower than the current collector foil 11.

[0069] Next, a solid electrolyte layer 13 is formed on the current collector foil 11 on which the electrode active material layer 12 has been formed. For example, a paste-like paint prepared by kneading a solid electrolyte and other materials together with a predetermined solvent is applied to the electrode active material layer 12 and the current collector foil 11 using a coating device or the like. At this time, a heat pressing treatment may be performed using a roll press or the like as needed. At this time, each solid electrolyte layer 13 is formed so that its edge is in contact with the current collector foil 11 and so as to cover the electrode active material layer 12 in an area narrower than the current collector foil 11.

[0070] Next, the protective portion 14 is formed on the side surface of the solid electrolyte layer 13. For example, a paste-like paint prepared by kneading SBR into a predetermined solvent is applied to the side surface of the solid electrolyte layer 13 using a coating device or the like. At this time, the paint is applied so that the cross section of the protective portion 14 in the stacking direction has an inclined shape that widens toward the current collector foil 11. The protective portions 14 of adjacent electrodes 10 are arranged so as to be in contact with each other. Note that the inclination angles of the protective portions 14 facing each other across the current collector foil 11 may be the same or different. As described above, the protective portion 14 only needs to cover at least two opposing side surfaces of the rectangular shape of the solid electrolyte layer 13.

[0071] By such an electrode sheet production process, it is possible to obtain an electrode sheet 20 in which electrodes 10 are continuously arranged, as shown in Fig. 6(a) . In Fig. 6(a) , the electrode sheet 20 includes three electrodes 10, but the number of electrodes included in the electrode sheet 20 is not particularly limited and may be from two to several hundred.

[0072] [Electrode Sheet Cutting Process] Next, the electrode sheet 20 obtained above is cut so that the ends of the current collector foil 11 and the protective portions 14 coincide in a plan view. More specifically, the electrode sheet 20 is cut between the protective portions 14 of adjacent electrodes 10. This prevents the positive electrode current collector and the negative electrode current collector from coming close to each other in a single cell, and prevents short circuits from occurring as a result. The portions where the electrode sheet 20 is cut in the electrode sheet cutting process of this embodiment are indicated by arrows in FIG. 6( a). Conventionally known cutting means, such as a cutting blade 30 shown in FIG. 6( b), can be used to cut the electrode sheet 20.

[0073] 6(b), the inclination angle of the protective portion 14 with respect to the current collecting foil 11 is preferably large enough to prevent the protective portion 14 from coming into contact with the cutting blade 30 when the electrode sheet 20 is cut by the cutting blade 30. With this configuration, it is possible to prevent the protective portion 14 from being damaged when the electrode sheet 20 is cut by the cutting blade 30, and the function of the protective portion 14 to protect the end of the solid electrolyte layer 13 can be fully exerted.

[0074] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and the technical scope of the present invention is not intended to be limited to the specific configurations of the above embodiments. Furthermore, the above embodiments can be combined as appropriate.

[0075] The following embodiments are also included within the scope of the present invention: a secondary battery electrode as defined in claim 1 having the features of claim 2; a secondary battery electrode as defined in claim 1 or 2 having the features of claim 3; a secondary battery electrode as defined in claim 3 having the features of claim 4; a secondary battery electrode as defined in claim 3 or 4 having the features of claim 5; a secondary battery electrode as defined in any one of claims 1 to 5 having the features of claim 6; a secondary battery electrode as defined in any one of claims 1 to 6 having the features of claim 7; a secondary battery electrode as defined in any one of claims 1 to 7 having the features of claim 8; a secondary battery electrode as defined in any one of claims 1 to 8 having the features of claim 9; a secondary battery electrode as defined in claim 9 having the features of claim 10; a secondary battery comprising a secondary battery electrode as defined in any one of claims 1 to 10; and a manufacturing method as defined in claim 12 having the features of claim 13.

[0076] 10...Electrode 11...Collector foil 12...Electrode active material layer 13...Solid electrolyte layer 14...Protective part

Claims

1. An electrode for a secondary battery comprising: a current collecting foil; an electrode active material layer containing an electrode active material and arranged on the surface of the current collecting foil; a solid electrolyte layer containing a solid electrolyte, covering the electrode active material layer and having an edge in contact with the current collecting foil; and a protective part having elasticity and arranged at a location where the edge contacts the current collecting foil, wherein a cross section of the protective part in the stacking direction has a sloping shape widening toward the current collecting foil, and the outer peripheral edge of the protective part coincides with the outer peripheral edge of the current collecting foil in plan view.

2. The electrode for a secondary battery according to claim 1, wherein the height of the protective portion from the current collecting foil is smaller than the thickness of the solid electrolyte layer.

3. The secondary battery electrode according to claim 1, wherein the solid electrolyte layer has a rectangular shape when viewed in plan.

4. The secondary battery electrode according to claim 3, wherein the protective portion is disposed on at least two opposing sides of the rectangular shape of the solid electrolyte layer.

5. An electrode for a secondary battery as described in claim 3 or 4, wherein the protective portion is arranged at least at a corner of the rectangular shape when viewed in a plane, and the outer peripheral edge of the protective portion corresponding to the corner has an R-shape.

6. An electrode for a secondary battery according to claim 1 or 3, wherein the electrode active material layer, the solid electrolyte layer, and the protective part are respectively arranged on both sides of the current collecting foil, and the inclination angle of the protective part arranged on one surface of the current collecting foil is different from the inclination angle of the protective part arranged at the opposing position on the other surface of the current collecting foil.

7. The electrode for a secondary battery according to claim 1 or 3, wherein the cross section in the stacking direction of the outer periphery of the electrode active material layer and the outer periphery of the solid electrolyte layer has an inclined shape that widens toward the current collecting foil.

8. The electrode for a secondary battery according to claim 1 or 3, wherein the material constituting the protective portion is a viscoelastic body.

9. The secondary battery electrode according to claim 1 or 3, wherein the material constituting the protective portion is a material that does not react with the solid electrolyte and exhibits electrical insulation properties.

10. The secondary battery electrode according to claim 9, wherein the protective portion is made of a material selected from the group consisting of resin and rubber.

11. A secondary battery comprising the electrode for a secondary battery according to claim 1 or 3.

12. A method for manufacturing an electrode for a secondary battery as defined in claim 1 or 3, comprising: forming the electrode active material layer, the solid electrolyte layer, and the protective portion on the surface of the current collector foil to produce an electrode sheet in which electrodes are continuously arranged; and cutting the electrode sheet between adjacent protective portions using cutting means.

13. A method for manufacturing an electrode for a secondary battery as described in claim 12, wherein the cutting means is a cutting blade, and the inclination angle of the protective part relative to the current collecting foil is such that the protective part does not come into contact with the cutting blade when the electrode sheet is cut by the cutting blade.

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