Electrode stack, method for producing same and electrochemical element

Abstract

The present invention provides: an electrode stack which can be used for assembly of an electrochemical element, while being capable of having a reduced internal resistance; a method for producing this electrode stack; and an electrochemical element which uses this electrode stack.　An electrode stack according to the present invention comprises a first electrode, a second electrode, and a separation layer that is interposed therebetween; at least one of the first electrode and the second electrode comprises an electrode mixture layer and a sheet-like porous metal base material; the porous metal base material is integrated with the electrode mixture layer by having at least a part thereof including the electrode mixture layer-side end embedded in the superficial part of the electrode mixture layer; and the other end of the porous metal base material is exposed in the surface of the electrode. An electrochemical element according to the present invention comprises an outer case which has a conduction path that leads to the outside, and an electrode stack according to the present invention; and a porous metal base material in the surface of an electrode of this electrode stack is brought into contact with the conduction path so that the electrode and the conduction path are electrically connected to each other.

Description

Electrode laminate, its manufacturing method and electrochemical element

[0001] The present invention relates to an electrode laminate that can be used to assemble an electrochemical device and that can reduce internal resistance, a method for producing the same, and an electrochemical device that uses the electrode laminate.

[0002] In recent years, with the development of portable electronic devices such as mobile phones and laptop personal computers, and the practical application of electric vehicles, there has been a growing demand for small, lightweight batteries with high capacity and high energy density.

[0003] Currently, lithium batteries, especially lithium ion batteries, that can meet this requirement use lithium cobalt oxide (LiCoO ２ ), lithium nickel oxide (LiNiO ２ ), graphite or the like is used as the negative electrode active material, and an organic electrolyte solution containing an organic solvent and a lithium salt is used as the non-aqueous electrolyte.

[0004] Furthermore, with the further development of devices to which lithium-ion batteries are applied, there is a demand for lithium-ion batteries with even longer life, higher capacity, and higher energy density, as well as a high demand for the reliability of lithium-ion secondary batteries with longer life, higher capacity, and higher energy density.

[0005] However, the organic electrolyte used in lithium-ion batteries contains flammable organic solvents, which can cause the organic electrolyte to generate excessive heat in the event of an abnormality such as a short circuit. Furthermore, with the recent trend toward higher energy density in lithium-ion batteries and an increasing amount of organic solvent in the organic electrolyte, there is a growing demand for greater reliability in lithium-ion batteries.

[0006] In light of the above, all-solid-state lithium batteries that do not use organic solvents are also being considered. All-solid-state lithium batteries use a molded body of a solid electrolyte that does not use an organic solvent instead of the conventional organic solvent-based electrolyte, and are therefore highly reliable without the risk of abnormal heat generation from the solid electrolyte.

[0007] Furthermore, because all-solid-state batteries are not only highly safe but also highly reliable, environmentally resistant, and have a long lifespan, they are expected to be maintenance-free batteries that can continue to contribute to social development while also contributing to safety and security. Providing all-solid-state batteries to society can contribute to the achievement of Goal 3 (Ensure healthy lives and promote well-being for all at all ages), Goal 7 (Ensure access to affordable, reliable, sustainable, and modern energy for all), Goal 11 (Make cities inclusive, safe, resilient, and sustainable cities and human settlements), and Goal 12 (Ensure sustainable consumption and production patterns) out of the 17 Sustainable Development Goals (SDGs) established by the United Nations.

[0008] Among batteries such as all-solid-state batteries, flat-shaped batteries known as coin batteries or button batteries are known. These flat-shaped batteries use an exterior body formed by interposing a gasket between an outer can and a sealing can and crimping the open end of the outer can inward. In batteries such as all-solid-state batteries that have electrodes (pellet-shaped electrodes) made of a molded body of an electrode mixture containing an active material, the outer can and the sealing can typically function as a conductive path connecting the inside to the outside of the battery, and the pellet-shaped electrode is brought into contact with the conductive path, allowing the outer can and the sealing can to function as a pair of electrode terminals, respectively.

[0009] However, when a pellet-shaped electrode is brought into contact with the conductive path, the conductive connection between the electrode and the conductive path is not sufficiently secured due to vibration or changes in the volume of the electrode during charging and discharging, which can easily lead to the problem of high internal resistance of the battery.

[0010] On the other hand, there have been proposals for technologies for reducing internal resistance in batteries having the above-described conductive paths. For example, Patent Document 1 discloses an all-solid-state lithium battery in which a current collector made of a metal mesh, foam metal, or the like is fixed at multiple locations to at least one of the battery case and sealing plate of the battery, so that the contact points between the current collector and the electrodes are movable with respect to the battery case or sealing plate, and the high spring elasticity of the current collector ensures sufficient contact between the current collector and the positive and negative electrodes of the battery pellets.

[0011] Furthermore, Patent Document 1 also discloses, as an alternative embodiment to the above, an all-solid-state lithium battery in which the current collector is embedded inside pellets of at least one of the positive and negative electrodes, thereby creating an electron conductive network throughout the electrodes and improving current collection efficiency. In the all-solid-state lithium battery described in Patent Document 1, these measures enable a reduction in internal resistance.

[0012] Furthermore, Patent Document 2 discloses a flat all-solid-state battery in which a flexible conductive porous member made of a graphite molded body is disposed between a laminate in which a positive electrode, a solid electrolyte layer, and a negative electrode are stacked and the inner bottom surface of an outer can or the inner bottom surface of a sealed can, thereby maintaining good contact between the electrode laminate and the battery case and ensuring excellent conductivity.

[0013] Japanese Patent Application Laid-Open No. 10-247516 International Publication No. 2020 / 066323

[0014] However, as described in Patent Document 1, when the electrode mixture layer is brought into movable contact with a current collector made of a highly rigid metal mesh, foamed metal, or the like, if the force pressing the contact surface is weak, electrical contact becomes insufficient, resulting in a problem of an increase in the internal resistance of the battery.Furthermore, when the current collector is simply embedded inside the electrode mixture layer, a conductive network of the current collector is formed in the electrode, which can reduce the resistance inside the electrode, but this does not result in a sufficient reduction in contact resistance between the electrode and the conductive path of the outer can, the sealed can, etc.

[0015] On the other hand, as described in Patent Document 2, when a porous molded graphite sheet is placed between the electrode stack and the battery container, the pressing force of the sheet can improve the state of conduction between the electrode stack and the battery container. However, there is room for further investigation to achieve a better conductive connection, including the material of the current collector.

[0016] The present invention has been made in view of the above circumstances, and its object is to provide an electrode laminate that can be used in assembling an electrochemical element and that can reduce internal resistance, a method for manufacturing the same, and an electrochemical element using the electrode laminate.

[0017] The electrode stack of the present invention comprises a first electrode, a second electrode, and an isolation layer interposed therebetween, and at least one of the first electrode and the second electrode comprises an electrode mixture layer and a sheet-like porous metal substrate, and at least a portion of the porous metal substrate, including the end on the electrode mixture layer side, is embedded in the surface layer of the electrode mixture layer and is integrated with the electrode mixture layer, and the other end of the porous metal substrate is exposed on the surface of the electrode.

[0018] The electrode laminate of the present invention can be produced by a production method of the present invention, which includes a first step of pouring an electrode mixture into a mold and pressurizing it to preform it, a second step of placing a sheet-like porous metal substrate on the electrode mixture preformed in the first step, and a third step of compressing the porous metal substrate by pressing it toward the electrode mixture, thereby embedding at least a portion of the porous metal substrate, including the end portion on the electrode mixture side, in the electrode mixture, and forming an electrode mixture layer integrated with the porous metal substrate.

[0019] The electrochemical element of the present invention comprises an outer casing and the electrode laminate of the present invention sealed inside the outer casing, wherein the outer casing has a conductive path leading from the inside to the outside, and the porous metal substrate on the surface of the electrode of the electrode laminate is in contact with the conductive path, thereby establishing electrical conduction between the electrode and the conductive path.

[0020] According to the present invention, it is possible to provide an electrode laminate that can be used to assemble an electrochemical device and that can reduce internal resistance, a method for producing the same, and an electrochemical device that uses the electrode laminate.

[0021] 1 is a scanning electron microscope photograph of a surface (surface of an electrode) in an example of an electrode laminate of the present invention. 2 is a cross-sectional view schematically showing an example of an electrochemical element of the present invention.

[0022] The electrode laminate of the present invention has a first electrode, a second electrode, and an isolation layer interposed therebetween, and at least one of the first electrode and the second electrode has an electrode mixture layer and a sheet-like porous metal substrate, and at least a portion of the porous metal substrate, including the end on the electrode mixture layer side, is embedded in the surface layer of the electrode mixture layer and is integrated with the electrode mixture layer, and the other end of the porous metal substrate is exposed on the surface of the electrode.

[0023] That is, in the electrode laminate of the present invention, at least one of the two electrodes has an electrode mixture layer and a sheet-like porous metal substrate, and a certain range in the thickness direction from the end (end face) of the porous metal substrate that functions as a current collector on the electrode mixture layer side is embedded in the surface layer portion of the electrode mixture layer. Therefore, the electrode mixture that constitutes the electrode mixture layer is held in at least a part of the pores of the porous metal substrate, and the porous metal substrate and the electrode mixture layer are integrated, thereby resulting in very good conductivity between the electrode mixture layer and the current collector.

[0024] In the electrode laminate of the present invention, the electrode has an electrode mixture layer and a sheet-like porous metal substrate, and the end (end face) of the porous metal substrate opposite to the electrode mixture layer side is exposed on the surface (surface of the electrode). Therefore, when an electrochemical element is constructed by using an exterior body having a conductive path connecting the inside to the outside and housing the electrode laminate of the present invention inside the exterior body, the porous metal substrate on the surface of the electrode is brought into contact with the conductive path, thereby providing very good conductivity between the electrode and the conductive path.

[0025] Due to this action, the electrode laminate of the present invention can reduce the internal resistance of an electrochemical device and improve its characteristics. That is, an electrochemical device of the present invention having the electrode laminate of the present invention has low internal resistance and excellent characteristics due to the above-mentioned action of the electrode laminate.

[0026] In the electrode laminate of the present invention, it is sufficient that either one of the first electrode and the second electrode has the above-mentioned configuration, i.e., has an electrode mixture layer and a sheet-like porous metal substrate, and at least a portion of the porous metal substrate, including the end portion on the electrode mixture layer side, is embedded in the surface layer portion of the electrode mixture layer to be integrated with the electrode mixture layer, and the other end portion of the porous metal substrate is exposed on the surface of the electrode, thereby reducing the internal resistance of the electrochemical element. However, from the viewpoint of further reducing the internal resistance and configuring an electrochemical element with better characteristics, it is preferable that both the first electrode and the second electrode have the above-mentioned configuration.

[0027] The electrochemical element of the present invention includes batteries, capacitors, etc. Furthermore, when the electrochemical element of the present invention is a battery, it includes primary batteries and secondary batteries, and also includes a battery having a solid electrolyte layer interposed between a positive electrode and a negative electrode (all-solid-state battery), and a battery (battery other than an all-solid-state battery) having a separator interposed between a positive electrode and a negative electrode and an electrolyte containing a solvent (a non-aqueous electrolyte solution, an aqueous electrolyte solution, or a gel electrolyte obtained by gelling such an electrolyte solution). Furthermore, when the electrochemical element of the present invention is a capacitor, it includes an electric double layer capacitor, a lithium ion capacitor, etc.

[0028] <Electrode Stack> The electrode stack has a first electrode, a second electrode, and an isolation layer interposed therebetween.

[0029] When the electrochemical device in which the electrode laminate is used is a battery or a lithium ion capacitor, one of the first electrode and the second electrode is a positive electrode and the other is a negative electrode. When the electrochemical device in which the electrode laminate is used is an electric double layer capacitor, the first electrode and the second electrode can have the same configuration.

[0030] At least one of the first electrode and the second electrode has, as described above, an electrode mixture layer and a sheet-like porous metal substrate, and at least a portion of the porous metal substrate, including the end portion on the electrode mixture layer side, is embedded in the surface layer portion of the electrode mixture layer and is integrated with the electrode mixture layer, and the other end portion of the porous metal substrate is exposed on the surface of the electrode.

[0031] In the electrode laminate used in the battery, when the electrode having the above-described configuration is a positive electrode, the electrode mixture layer is composed of a positive electrode mixture containing a positive electrode active material and the like.

[0032] When the electrode having the above-described structure is used as the positive electrode of a primary battery, the positive electrode active material can be the same as the positive electrode active material used in conventionally known non-aqueous electrolyte primary batteries, alkaline batteries, manganese batteries, etc. Specifically, for example, manganese dioxide, lithium-containing manganese oxide (e.g., LiMn ３ O ６ or a composite oxide having the same crystal structure as manganese dioxide (e.g., β-type, γ-type, or a mixed structure of β-type and γ-type) and a Li content of 3.5% by mass or less, preferably 2% by mass or less, more preferably 1.5% by mass or less, particularly preferably 1% by mass or less); ａ Ti ５／３ O ４ (4 / 3≦a<7 / 3) and other lithium-containing composite oxides; vanadium oxide; niobium oxide; titanium oxide; sulfides such as iron disulfide; graphite fluoride; Ag ２ Silver sulfides such as S; NiO ２ Nickel oxides such as:

[0033] When the electrode having the above-described structure is used as the positive electrode of a secondary battery, the positive electrode active material can be the same as the positive electrode active material used in conventionally known non-aqueous electrolyte secondary batteries, alkaline secondary batteries, etc. Specifically, Li １－ｘ M ｒ Mn ２－ｒ O ４(wherein M is at least one element selected from the group consisting of Li, Na, K, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Zr, Fe, Co, Ni, Cu, Zn, Al, Sn, Sb, In, Nb, Ta, Mo, W, Y, Ru, and Rh, and 0≦x≦1, 0≦r≦1), a spinel-type lithium manganese composite oxide represented by Li ｒ Mn （１－ｓ－ｔ） Ni ｓ M ｔ O （２－ｕ） F ｖ (wherein M is at least one element selected from the group consisting of Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, Zr, Mo, Sn, Ca, Sr, and W, and 0≦r≦1.2, 0<s<0.5, 0≦t≦0.5, u+v<1, −0.1≦u≦0.2, 0≦v≦0.1), a layered compound represented by １－ｘ Co １－ｒ M ｒ O ２ (wherein M is at least one element selected from the group consisting of Al, Mg, Ti, V, Cr, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0≦x≦1, 0≦r≦0.5), lithium cobalt composite oxide represented by Li １－ｘ Ni １－ｒ M ｒ O ２ (wherein M is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, and Ba, and 0≦x≦1, 0≦r≦0.5), lithium nickel composite oxide represented by Li １＋ｓ－ｘ M １－ｒ N ｒ P.O. ４ F ｓ (wherein M is at least one element selected from the group consisting of Fe, Mn, and Co, and N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, V, and Ba, and 0≦x≦1, 0≦r≦0.5, 0≦s≦1), Li ２－ｘ M １－ｒ N ｒ P２ O ７ (wherein M is at least one element selected from the group consisting of Fe, Mn, and Co, and N is at least one element selected from the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb, V, and Ba, and 0≦x≦2, 0≦r≦0.5), nickel hydroxide, silver oxide, and the like can be exemplified, and only one of these may be used, or two or more of them may be used in combination.

[0034] When the electrochemical device is an all-solid-state secondary battery, the average particle size of the positive electrode active material is preferably 1 μm or more, more preferably 2 μm or more, and preferably 10 μm or less, more preferably 8 μm or less. The positive electrode active material may be primary particles or secondary particles formed by aggregation of primary particles. When a positive electrode active material having an average particle size within the above range is used, a large interface with the solid electrolyte contained in the positive electrode can be secured, thereby further improving the output characteristics of the battery.

[0035] The average particle diameter of various particles (positive electrode active material, solid electrolyte, etc.) referred to in this specification is the 50% diameter value (D) in the volume-based integrated fraction when the integrated volume is calculated from particles with small particle sizes using a particle size distribution measuring device (e.g., a Microtrac particle size distribution measuring device "HRA9320" manufactured by Nikkiso Co., Ltd.). ５０ ) means

[0036] When the electrochemical device is an all-solid-state secondary battery, the positive electrode active material preferably has a reaction suppression layer on its surface to suppress reaction with the solid electrolyte contained in the positive electrode.

[0037] If the positive electrode active material and the solid electrolyte come into direct contact in the electrode mixture layer (positive electrode mixture layer), the solid electrolyte may oxidize to form a resistance layer, which may reduce ionic conductivity in the electrode mixture layer. By providing a reaction suppression layer that suppresses reaction with the solid electrolyte on the surface of the positive electrode active material and preventing direct contact between the positive electrode active material and the solid electrolyte, it is possible to suppress a reduction in ionic conductivity in the electrode mixture layer due to oxidation of the solid electrolyte.

[0038] The reaction suppression layer may be made of a material that has ion conductivity and can suppress the reaction between the positive electrode active material and the solid electrolyte. Examples of materials that can form the reaction suppression layer include oxides containing Li and at least one element selected from the group consisting of Nb, P, B, Si, Ge, Ti, and Zr, more specifically, LiNbO ３ Nb-containing oxides such as Li ３ P.O. ４ , Li ３ BO ３ , Li ４ SiO ４ , Li ４ GeO ４ , LiTiO ３ , LiZrO ３ , Li ２ WO ４ The reaction suppression layer may contain only one of these oxides, or may contain two or more of them, or may contain a composite compound of two or more of these oxides. Among these oxides, it is preferable to use an Nb-containing oxide, such as LiNbO ３ It is more preferable to use

[0039] The reaction suppression layer is preferably present on the surface in an amount of 0.1 to 1.0 part by mass per 100 parts by mass of the positive electrode active material, which allows for effective suppression of the reaction between the positive electrode active material and the solid electrolyte.

[0040] Examples of methods for forming a reaction suppression layer on the surface of a positive electrode active material include the sol-gel method, mechanofusion method, CVD method, PVD method, and ALD method.

[0041] The content of the positive electrode active material in the positive electrode mixture is preferably 60 to 85 mass % from the viewpoint of increasing the energy density of the electrochemical device.

[0042] The positive electrode mixture may contain a conductive additive. Specific examples thereof include carbon materials such as graphite (natural graphite, artificial graphite), graphene, carbon black, carbon nanofibers, and carbon nanotubes. ２When S is used, conductive Ag is generated during the discharge reaction, so the conductive additive does not need to be contained. When the conductive additive is contained in the positive electrode mixture, the content thereof is preferably 1.0 part by mass or more, preferably 7.0 parts by mass or less, and more preferably 6.5 parts by mass or less, relative to 100 parts by mass of the positive electrode active material.

[0043] The positive electrode mixture may contain a binder. Specific examples include fluororesins such as polyvinylidene fluoride (PVDF). Note that, for example, when a sulfide-based solid electrolyte is contained in the positive electrode mixture (described in detail below), the positive electrode mixture may not contain a binder if good moldability can be ensured in forming the electrode mixture layer (positive electrode mixture layer) without using a binder.

[0044] When a binder is required in the positive electrode mixture, the content thereof is preferably 15% by mass or less, and preferably 0.5% by mass or more. On the other hand, when moldability can be obtained without the binder in the positive electrode mixture, the content thereof is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and even more preferably 0% by mass (i.e., no binder is contained).

[0045] When the electrochemical device is an all-solid-state battery (all-solid-state primary battery, all-solid-state secondary battery), it is preferable that the positive electrode mixture contains a solid electrolyte.

[0046] The solid electrolyte contained in the positive electrode mixture is not particularly limited as long as it has lithium ion conductivity, and for example, a sulfide-based solid electrolyte, a hydride-based solid electrolyte, a halide-based solid electrolyte, an oxide-based solid electrolyte, etc. can be used.

[0047] The sulfide-based solid electrolyte is Li ２ S-P ２ S ５ , Li ２ S-SiS ２ , Li ２ S-P ２ S ５ -GeS ２ , Li ２S-B ２ S ３ In addition to particles of glass, thio-LISICON type particles [Li １０ GeP ２ S １２ , Li ９．５４ Si １．７４ P １．４４ S １１．７ Cl ０．３ The general formula Li12-12a-b+c+6d-eM is exemplified by １ ３＋ａ－ｂ－ｃ－ｄ M ２ ｂ M ３ ｃ M ４ ｄ M ５ １２－ｅ X ｅ (However, M １ is Si, Ge or Sn, M ２ is P or V, M ３ is Al, Ga, Y or Sb, M ４ is Zn, Ca, or Ba, M ５ is either S or S and O, and X is F, Cl, Br or I; 0≦a<3, 0≦b+c+d≦3, 0≦e≦3)], or one having an argyrodite-type crystal structure, which will be exemplified later, can also be used.

[0048] Examples of hydride-based solid electrolytes include LiBH ４ , LiBH ４ and a solid solution of the following alkali metal compound (e.g., LiBH ４ and the alkali metal compound in a molar ratio of 1:1 to 20:1. The alkali metal compound in the solid solution may be at least one selected from the group consisting of lithium halides (LiI, LiBr, LiF, LiCl, etc.), rubidium halides (RbI, RbBr, RbF, RbCl, etc.), cesium halides (CsI, CsBr, CsF, CsCl, etc.), lithium amide, rubidium amide, and cesium amide.

[0049] Examples of halide-based solid electrolytes include monoclinic LiAlCl４ , defect spinel type or layer structure LiInBr ４ , monoclinic Li ６－３ｍ Y ｍ X ６ (wherein 0 < m < 2 and X = Cl or Br), and other known compounds described in, for example, WO 2020 / 070958 and WO 2020 / 070955 can also be used.

[0050] As the oxide-based solid electrolyte, for example, garnet-type Li ７ La ３ Zr ２ O １２ , NASICON type Li １＋Ｏ Al １＋Ｏ Ti ２－Ｏ (P.O. ４ ) ３ , Li １＋ｐ Al １＋ｐ Ge ２－ｐ (P.O. ４ ) ３ , perovskite-type Li ３ｑ La ２／３－ｑ TiO ３ Examples include:

[0051] Among these solid electrolytes, sulfide-based solid electrolytes are preferred due to their high lithium ion conductivity, sulfide-based solid electrolytes containing Li and P are more preferred, and sulfide-based solid electrolytes having an argyrodite-type crystal structure are even more preferred due to their higher lithium ion conductivity and high chemical stability.

[0052] Examples of sulfide-based solid electrolytes having an argyrodite-type crystal structure include Li ６ P.S. ５ Those represented by the following general composition formula (1) or the following general composition formula (2), such as Cl, are particularly preferred.

[0053] Li ７－ｘ＋ｙ P.S. ６－ｘ Cl ｘ＋ｙ (1)

[0054] In the general composition formula (1), 0.05≦y≦0.9 and −3.0x+1.8≦y≦−3.0x+5.7.

[0055] Li ７－ａ P.S. ６－ａ Cl ｂ Br ｃ (2)

[0056] In the general composition formula (2), a=b+c, ​​0<a≦1.8, and 0.1≦b / c≦10.0.

[0057] The average particle size of the solid electrolyte is preferably 0.1 μm or more, and more preferably 0.2 μm or more, from the viewpoint of reducing grain boundary resistance, while it is preferably 10 μm or less, and more preferably 5 μm or less, from the viewpoint of forming a sufficient contact interface between the active material and the solid electrolyte.

[0058] From the viewpoint of further increasing the ionic conductivity in the positive electrode and further improving the output characteristics of the electrochemical device, the content of the solid electrolyte in the positive electrode mixture is preferably 10 parts by mass or more, and more preferably 15 parts by mass or more, when the content of the positive electrode active material is 100 parts by mass. However, if the amount of solid electrolyte in the positive electrode mixture is too large, the amounts of other components may be reduced, and the effects of these components may be reduced. Therefore, the content of solid electrolyte in the positive electrode mixture is preferably 65 parts by mass or less, and more preferably 60 parts by mass or less, when the content of the positive electrode active material is 100 parts by mass.

[0059] In the electrode laminate used in the battery, when the electrode having the above-described configuration is a negative electrode, the electrode mixture layer is composed of a negative electrode mixture containing a negative electrode active material and the like.

[0060] Examples of the negative electrode active material include carbon materials such as graphite, lithium titanium oxides (lithium titanate, etc.), simple substances containing elements such as Si and Sn, compounds (oxides, etc.), and alloys thereof. Lithium metal and lithium alloys (lithium-aluminum alloys, lithium-indium alloys, etc.) can also be used as the negative electrode active material.

[0061] The content of the negative electrode active material in the negative electrode mixture is preferably 40 to 80 mass % from the viewpoint of increasing the energy density of the battery.

[0062] The negative electrode mixture may contain a conductive additive. Specific examples include the same conductive additives as those exemplified above as the conductive additives that may be contained in the positive electrode mixture. The content of the conductive additive in the negative electrode mixture is preferably 10 to 30 parts by mass, relative to 100 parts by mass of the negative electrode active material.

[0063] The negative electrode mixture may contain a binder. Specific examples thereof include the same binders as those exemplified above as binders that may be contained in the positive electrode mixture. Note that, for example, when a sulfide-based solid electrolyte is contained in the negative electrode mixture (described later), if good formability can be ensured in forming the electrode mixture layer (negative electrode mixture layer) without using a binder, the negative electrode mixture may not contain a binder.

[0064] When a binder is required in the negative electrode mixture, the content thereof is preferably 15% by mass or less, and preferably 0.5% by mass or more. On the other hand, when moldability can be obtained without the binder in the negative electrode mixture, the content thereof is preferably 0.5% by mass or less, more preferably 0.3% by mass or less, and even more preferably 0% by mass (i.e., no binder is contained).

[0065] When the electrochemical device is an all-solid-state battery, it is preferable that the negative electrode mixture contains a solid electrolyte. Specific examples thereof include the same solid electrolytes as those exemplified above as those that can be contained in the positive electrode mixture. Among the solid electrolytes exemplified above, it is preferable to use a sulfide-based solid electrolyte because it has high lithium ion conductivity and also has the function of improving the formability of the negative electrode mixture. It is more preferable to use a sulfide-based solid electrolyte having an argyrodite-type crystal structure, and it is even more preferable to use one represented by the general composition formula (1) or the general composition formula (2).

[0066] For the same reasons as in the case of the positive electrode mixture, the average particle size of the solid electrolyte in the negative electrode mixture is preferably 0.1 μm or more, more preferably 0.2 μm or more, and is preferably 10 μm or less, more preferably 5 μm or less.

[0067] From the viewpoint of further increasing ionic conductivity in the negative electrode and further improving the output characteristics of the electrochemical device, the content of the solid electrolyte in the negative electrode mixture is preferably 30 parts by mass or more, and more preferably 35 parts by mass or more, relative to 100 parts by mass of the negative electrode active material. However, if the amount of solid electrolyte in the negative electrode mixture is too large, the amounts of other components may be reduced, and the effects of these components may be reduced. Therefore, the content of solid electrolyte in the negative electrode mixture is preferably 130 parts by mass or less, and more preferably 110 parts by mass or less, relative to 100 parts by mass of the negative electrode active material.

[0068] When the electrochemical element in which the electrode laminate is used is an electric double layer capacitor, the electrode mixture layer of the electrode having the above-described configuration can be formed from an electrode mixture having the same configuration as the positive electrode mixture, except that activated carbon is used as the active material.

[0069] Furthermore, when the electrochemical element in which the electrode laminate is used is a lithium ion capacitor, the electrode mixture layer of the electrode having the above-described configuration can be formed from an electrode mixture having the same configuration as the electrode mixture for the electrode of the electric double layer capacitor if this electrode is a positive electrode, and can be formed from an electrode mixture having the same configuration as the above-described negative electrode mixture if this electrode is a negative electrode.

[0070] In an electrode having the above configuration, it is preferable to use a foamed metal porous body as the porous metal substrate. Specific examples of foamed metal porous bodies include "Celmet (registered trademark)" from Sumitomo Electric Industries, Ltd. Such porous metal substrates are usually compressed and reduced in thickness when preparing an electrode together with an electrode mixture, so that the thickness before use in an electrode (electrode laminate) is greater than the thickness (thickness within the electrode). For example, the thickness of the porous metal substrate before compression is preferably 0.1 mm or more, more preferably 0.3 mm or more, and particularly preferably 0.5 mm or more, while preferably 3 mm or less, more preferably 2 mm or less, and particularly preferably 1.5 mm or less. The porous metal substrate is compressed in the thickness direction during the production of the electrode laminate described below, and its thickness becomes the value described below.

[0071] The porosity of the porous metal substrate before compression is preferably 80% or more, more preferably 90% or more, and particularly preferably 95% or more, so that the electrode mixture can be easily filled into the pores of the porous metal substrate in the step of pressurizing the porous metal substrate and the electrode mixture layer, and the porous metal substrate and the electrode mixture layer can be easily integrated. On the other hand, in order to increase the amount of the substrate by a certain amount or more and to increase the conductivity, the porosity is preferably 99.5% or less, more preferably 99% or less, and particularly preferably 98.5% or less.

[0072] When only one of the first electrode and the second electrode in the electrode laminate has the above-described configuration, the other electrode can be, for example, a molded body of an electrode mixture (such as an electrode consisting of only a pellet, or an electrode having a structure in which a molded body of an electrode mixture (electrode mixture layer) is formed on a current collector (such as a current collector other than a porous metal substrate, such as a metal foil)), a lithium sheet, a lithium alloy sheet, or other metal sheet that functions as a negative electrode active material (when the electrochemical element is a battery and the electrode is its negative electrode), or the like.

[0073] In an electrode having the above configuration, the thickness of the portion of the porous metal substrate that is embedded in the electrode mixture layer is preferably 10% or more, and more preferably 20% or more, of the thickness of the porous metal substrate (the thickness of the entire porous metal substrate, including the thickness of the portion where the electrode mixture layer coexists; unless otherwise specified, the same applies hereinafter to the thickness of the porous metal substrate), from the viewpoint of more reliably integrating the porous metal substrate and the electrode mixture layer.

[0074] In an electrode having the above configuration, in order to reduce the resistance when in contact with the conductive path in the exterior body of an electrochemical element, it is desirable that the end of the porous metal substrate opposite the electrode mixture layer side (hereinafter sometimes referred to as the surface side end) is not embedded in the electrode mixture layer, and the end of the electrode (surface of the electrode) is composed only of the porous metal substrate. That is, during the production of the electrode laminate described below, when the porous metal substrate is compressed in the thickness direction, it is desirable that the pores at the surface side end of the porous metal substrate are crushed and disappear, and only the porous metal substrate is exposed to the surface of the electrode. However, some of the pores at the surface side end of the porous metal substrate are not crushed and remain as pores, or may be filled with an electrode mixture, and a portion of the electrode mixture may be exposed to the surface of the electrode together with the surface side end of the porous metal substrate, as long as it does not significantly affect the contact resistance with the conductive path. That is, as long as the surface side end of the porous metal substrate can be exposed to the electrode surface, the entire porous metal substrate (100% of the thickness of the porous metal substrate) may be embedded in the surface layer portion of the electrode mixture layer. By filling the pores of the porous metal substrate with the electrode mixture up to the surface of the electrode, the electrode mixture and the porous metal substrate can be more reliably integrated.

[0075] A scanning electron microscope (SEM) photograph of the surface of an example of the electrode laminate of the present invention is shown in Figure 1. On the surface of the electrode laminate (surface of the electrode) shown in Figure 1, the end of the porous metal substrate 10 of the electrode having the above-mentioned configuration related to the electrode laminate is exposed, and part of the electrode mixture 11 is also exposed on the surface of the electrode by entering into pores present at the end of the porous metal substrate.

[0076] However, since the contact resistance between the porous metal substrate and the conductive path of the electrochemical element increases as the proportion (area ratio) of the electrode mixture exposed on the surface of the electrode increases, it is desirable that the proportion of the area of ​​the exposed electrode mixture on the electrode surface be 50% or less in plan view, more desirably 25% or less, even more desirably 15% or less, and particularly desirably 10% or less.

[0077] In the electrode having the above configuration, when at least a portion of the porous metal substrate is embedded in the surface layer of the electrode mixture layer, from the viewpoint of more reliably integrating the porous metal substrate and the electrode mixture layer, the thickness of the porous metal substrate is preferably 1% or more of the total thickness of the electrode mixture layer (including the thickness of the portion coexisting with the porous metal substrate. Unless otherwise specified, the "thickness of the electrode mixture layer" referred to below means the "total thickness of the electrode mixture layer"). It is more preferably 2% or more, and particularly preferably 3% or more. Furthermore, from the viewpoint of improving the filling property of the electrode mixture layer in the electrode, the thickness of the porous metal substrate is preferably 30% or less of the thickness of the electrode mixture layer, more preferably 20% or less, and particularly preferably 10% or less.

[0078] In the electrode having the above configuration, the thickness of the porous metal substrate is preferably 10 μm or more, more preferably 20 μm or more, and particularly preferably 30 μm or more, while it is preferably 300 μm or less, more preferably 200 μm or less, and particularly preferably 100 μm or less. The thickness of the electrode mixture layer is preferably 0.2 mm or more, more preferably 0.5 mm or more, and particularly preferably 0.7 mm or more, while it is preferably 2 mm or less, more preferably 1.7 mm or less, and particularly preferably 1.5 mm or less.

[0079] The thickness of the porous metal substrate and the thickness of the electrode mixture layer in the electrode laminate are determined by the maximum thickness-wise width of the region where the porous metal substrate can be confirmed and the region where the electrode mixture can be confirmed in an image of a cross section of the electrode in the thickness direction observed with an SEM at a magnification of 50 to 1000 times. The thickness of the portion of the porous metal substrate embedded in the electrode mixture layer is determined by the maximum thickness-wise width of the portion where the region where the porous metal substrate can be confirmed and the region where the electrode mixture can be confirmed overlap (the values ​​in the examples described below are determined by these methods).

[0080] The proportion (area ratio) of the electrode mixture exposed on the surface of the electrode can be determined by the ratio (A / B) of the total area of ​​the exposed electrode mixture (A) to the area of ​​the entire electrode (B) in an image of the electrode surface observed with an SEM at a magnification of 50 to 200 times (the values ​​in the examples described later are determined by this method).

[0081] In the electrode laminate, an isolating layer is interposed between the first electrode and the second electrode, but in batteries and capacitors that do not use an electrolyte containing a solvent, such as all-solid-state batteries, a solid electrolyte layer is used as the isolating layer.

[0082] Specific examples of the solid electrolyte constituting the solid electrolyte layer include the same solid electrolytes as those exemplified above as those that can be contained in the positive electrode mixture. Among the solid electrolytes exemplified above, it is preferable to use a sulfide-based solid electrolyte because it has high lithium ion conductivity and also has the function of improving the formability of the negative electrode mixture. It is more preferable to use a sulfide-based solid electrolyte having an argyrodite-type crystal structure, and it is even more preferable to use one represented by the general composition formula (1) or the general composition formula (2).

[0083] The solid electrolyte layer may have a porous body such as a resin nonwoven fabric as a support.

[0084] The thickness of the solid electrolyte layer is preferably 10 to 200 μm.

[0085] In electrode stacks used in batteries and capacitors that use electrolytes containing a solvent, a separator is used as an isolating layer interposed between a first electrode and a second electrode.

[0086] The separator should have sufficient strength and be able to retain a large amount of electrolyte. From this viewpoint, a microporous film or nonwoven fabric containing polyethylene, polypropylene, or an ethylene-propylene copolymer, having a thickness of 10 to 50 μm and an opening ratio of 30 to 70%, is preferred.

[0087] The electrode laminate can be produced by a production method including the following first to third steps.

[0088] In the first step, the electrode mixture is placed in a mold and pressurized to form a preform. The surface pressure of the preform in the first step is preferably, for example, 30 to 500 MPa.

[0089] In the next step, a porous metal substrate is placed on the electrode mixture preformed in step 1, and in the next step, the porous metal substrate is pressed and compressed toward the electrode mixture in step 3. By applying pressure in step 3, at least a portion of the porous metal substrate, including the end portion on the electrode mixture side, is embedded in the electrode mixture, and an electrode mixture layer is formed that is integrated with the porous metal substrate.

[0090] As described above, in this third step, the porous metal substrate is compressed in the thickness direction, and the degree of compression is, from the viewpoint of more reliably forming the porous metal substrate and the electrode mixture layer, preferably the thickness of the porous metal substrate after compression is 30% or less of the thickness before compression, more preferably 20% or less, and particularly preferably 10% or less. Furthermore, from the viewpoint of retaining a certain amount or more of the electrode mixture in the pores of the porous metal substrate and increasing the bonding strength between the porous metal substrate and the electrode mixture layer, the thickness of the porous metal substrate after compression in the third step is preferably 1% or more of the thickness before compression, more preferably 2% or more.

[0091] The surface pressure during the pressurization in the third step is preferably 800 MPa or more, more preferably 1000 MPa or more, and particularly preferably 1200 MPa or more, for example, in order to compress and mold the electrode mixture and sufficiently increase the density of the electrode mixture layer. Although the upper limit of the surface pressure during the pressurization in the third step is not particularly specified, in a general pressurization device, the upper limit is usually about 2000 MPa.

[0092] By going through the first to third steps, an electrode can be obtained in which at least a portion of the porous metal substrate, including the end portion on the electrode mixture layer side (a certain range in the thickness direction from the end portion of the porous metal substrate), is embedded in the surface layer portion of the electrode mixture layer and is integrated with the electrode mixture layer, and the other end portion of the porous metal substrate is exposed on the surface of the electrode.

[0093] If the surface pressure during the application of pressure in the third step becomes too high, cracks may occur when the porous metal substrate is compressed. However, even if the substrate is broken into pieces, the ends of the pieces can contribute to reducing the contact resistance if they are exposed on the surface of the electrode.

[0094] When manufacturing an electrode laminate having a separator, two electrodes obtained as described above can be prepared and placed on both sides of the separator to form an electrode laminate. The electrode placed on one side of the separator can also be an electrode other than the electrode having the above configuration (such as an electrode consisting of only a molded body of an electrode mixture without a current collector, or an electrode using a metal foil or the like as a current collector).

[0095] When manufacturing an electrode laminate having a solid electrolyte layer, two electrodes obtained as described above are prepared, and these are placed on both sides of the solid electrolyte layer, and if necessary, pressed to form an electrode laminate. Furthermore, the electrode placed on one side of the solid electrolyte layer can also be an electrode other than the electrode having the above configuration (such as an electrode consisting of only a molded body of an electrode mixture without a current collector, or an electrode using a metal foil or the like as a current collector).

[0096] Furthermore, when manufacturing an electrode laminate having a solid electrolyte layer, a preliminary step of putting the solid electrolyte into a mold and pressurizing it to preform it can be provided before the first step, and the electrode mixture can be placed on the solid electrolyte preformed in this preliminary step, after which the first step can be carried out.

[0097] The surface pressure during preforming in the preliminary step is preferably set to, for example, 30 to 120 MPa.

[0098] Alternatively, an electrode laminate having electrodes of the above-described configuration on both sides of a solid electrolyte layer can be manufactured by carrying out the preliminary step, the first step, the second step, and the third step, and then sequentially carrying out the first step, the second step, and the third step on one side of the solid electrolyte layer having electrodes of the above-described configuration on the other side of the solid electrolyte layer.

[0099] <Electrochemical element> The electrochemical element of the present invention comprises an exterior body and the electrode laminate of the present invention sealed inside the exterior body, the exterior body having a conductive path leading from the inside to the outside of the exterior body, and the porous metal substrate on the surface of the electrode of the electrode laminate is in contact with the conductive path, thereby establishing electrical conduction between the electrode and the conductive path.

[0100] Fig. 2 is a cross-sectional view schematically illustrating an example of an electrochemical element of the present invention. The electrochemical element 100 shown in Fig. 2 includes an electrode stack 140 having a first electrode 110, a second electrode 120, and an isolation layer 130 interposed therebetween, and is enclosed in an exterior body formed of a metal outer can 150, a metal sealing can 160, and a resin gasket 170 interposed therebetween. The sealing can 160 is fitted into the opening of the outer can 150 via the gasket 170, and the open end of the outer can 150 is tightened inward, thereby bringing the gasket 170 into contact with the sealing can 160, thereby sealing the opening of the outer can 150 and forming a sealed structure inside the element.

[0101] When the electrode stack 140 has a solid electrolyte layer as the isolation layer 130, for example, only the electrode stack 140 is enclosed within the exterior body. On the other hand, when the electrode stack 140 has a separator as the isolation layer 130, an electrolyte (not shown) is enclosed within the exterior body together with the electrode stack 140.

[0102] The first electrode 110 has an electrode mixture layer 111 and a porous metal substrate 112. The entire porous metal substrate 112, including the end on the electrode mixture layer 111 side, is embedded in the surface layer of the electrode mixture layer 111. That is, the entire location of the porous metal substrate 112 corresponds to the region where the electrode mixture layer and the porous metal substrate coexist, i.e., the surface layer of the electrode mixture layer. Furthermore, in the first electrode 110, the end of the porous metal substrate 112 on the opposite side to the electrode mixture layer 111 side (the lower end in FIG. 2 ) is exposed to the surface. Note that the dotted line in the first electrode 110 indicates the boundary between the region in the electrode mixture layer 111 where the porous metal substrate does not coexist and the region where the electrode mixture layer and the porous metal substrate coexist, and corresponds to the end of the porous metal substrate 112 on the electrode mixture layer 111 side.

[0103] The second electrode 120 has an electrode mixture layer 121 and a porous metal substrate 122, and the entire porous metal substrate 122, including the end on the electrode mixture layer 121 side, is embedded in the surface layer of the electrode mixture layer 121. That is, the entire location of the porous metal substrate 122 corresponds to the region where the electrode mixture layer and the porous metal substrate coexist, i.e., the surface layer of the electrode mixture layer. Furthermore, in the second electrode 120, the end of the porous metal substrate 122 on the opposite side to the electrode mixture layer 121 side (the upper end in FIG. 2 ) is exposed to the surface. Note that the dotted line in the second electrode 120 indicates the boundary between the region in the electrode mixture layer 121 where the porous metal substrate does not coexist and the region where the electrode mixture layer and the porous metal substrate coexist, and corresponds to the end of the porous metal substrate 122 on the electrode mixture layer 121 side.

[0104] 2 , a metal outer can 150 forms a conductive path on the first electrode 110 side, and the first electrode 110 and the outer can 150 (the conductive path formed by the outer can 150) are electrically connected by contacting the end of the porous metal substrate 112 exposed on the surface of the first electrode 110 with the inner surface of the outer can 150. The outer surface of the outer can 150 serves as an external terminal that electrically connects the electrochemical element to an external device.

[0105] 2, the metal sealing can 160 forms a conductive path on the second electrode 120 side, and the second electrode 120 and the sealing can 160 (the conductive path formed by the sealing can 160) are electrically connected by contacting the end of the porous metal substrate 122 exposed on the surface of the second electrode 120 with the inner surface of the sealing can 160. The outer surface of the sealing can 160 serves as an external terminal that electrically connects the electrochemical device to an external device.

[0106] The exterior of the electrochemical element is, for example, a case having an exterior can and a sealing can as shown in Fig. 2. That is, an electrochemical element having such a case as an exterior is coin-shaped (button-shaped).

[0107] In the case where the exterior body of the electrochemical element has an exterior can and a sealing can, examples include a case where the exterior can and the sealing can are crimped and sealed with a gasket, as shown in FIG. 2, and a case where the exterior can and the sealing can are bonded with a resin.

[0108] The outer can and the sealing can can be made of stainless steel or the like. The gasket can be made of polypropylene, nylon, or the like. If heat resistance is required for the application of the electrochemical element, a heat-resistant resin with a melting point exceeding 240°C, such as a fluororesin such as tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyphenylene ether (PEE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), or polyetheretherketone (PEEK), can also be used. If the electrochemical element is used in an application requiring heat resistance, a glass hermetic seal can be used for sealing.

[0109] The exterior body of the electrochemical element is not limited to one having an exterior can and a sealing can, as long as it has a conductive path that runs from the inside to the outside of the exterior body and is configured so that the porous metal substrate on the surface of the electrode of the electrode laminate comes into contact with the conductive path, thereby enabling electrical continuity between the electrode and the conductive path. For example, a ceramic case in which a conductive path made of a metal such as gold, platinum, silver, palladium, copper, nickel, or cobalt or an alloy thereof is provided so as to penetrate through the constituent materials can also be used as the exterior body of the electrochemical element.

[0110] The shape of the exterior body of the electrochemical element in plan view may be circular or polygonal, such as quadrilateral (square or rectangle).

[0111] In the case of an electrochemical element having an electrode laminate with a separator as a separator layer, an electrolyte is used as described above. The electrolyte is typically a liquid electrolyte (non-aqueous electrolyte solution or aqueous electrolyte solution) containing a non-aqueous solvent or an aqueous solvent. The non-aqueous electrolyte solution is an organic solvent in which an electrolyte salt such as a lithium salt is dissolved. The organic solvent is not particularly limited, but examples include: chain esters such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate; cyclic esters with high dielectric constants such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate; and mixed solvents of chain esters and cyclic esters. Mixed solvents in which a chain ester is the main solvent and a cyclic ester are particularly suitable.

[0112] The electrolyte salt to be dissolved in the organic solvent in preparing the non-aqueous electrolyte solution is, for example, LiPF when the electrochemical device is a battery or a lithium ion capacitor. ６ , LiBF ４ , LiAsF ６ , LiSbF ６ , LiCF ３ SO ３ , LiC ４ F ９ SO ３ , LiCF ３ CO ２ , Li ２ C ２ F ４ (SO ３ ) ２ , LiC ｎ F ２ｎ＋１ SO ３ (n≧2), LiN(RfSO ２ ) (Rf'SO ２ ), LiC(RfSO ２ ) ３ , LiN(RfOSO ２ ) ２ [wherein Rf and Rf' are fluoroalkyl groups] may be used alone or in combination of two or more. When the electrochemical element is an electric double layer capacitor, the electrolyte salt for the non-aqueous electrolyte solution may be (C ２ H ５ )４ NBF ４ , (C ２ H ５ ) ４ PBF ４ etc. are used.

[0113] The concentration of the electrolyte salt in the electrolytic solution is not particularly limited, but is preferably 0.3 mol / L or more, more preferably 0.4 mol / L or more, and is preferably 1.7 mol / L or less, more preferably 1.5 mol / L or less.

[0114] As the aqueous electrolyte, an alkaline aqueous solution (alkaline electrolyte) made of an aqueous solution of an alkali metal hydroxide such as potassium hydroxide, sodium hydroxide, or lithium hydroxide, or an aqueous solution having a pH in the range of 3 to 12, can be used.

[0115] The concentration of the alkali metal hydroxide in the alkaline electrolyte can be, for example, 25 to 40 mass %.

[0116] Examples of aqueous solutions having a pH in the range of 3 to 12 include solutions prepared by dissolving one or more of the following electrolyte salts in water: chlorides such as sodium chloride, potassium chloride, magnesium chloride, calcium chloride, ammonium chloride, and zinc chloride; hydroxides of alkali metals and alkaline earth metals (sodium hydroxide, potassium hydroxide, magnesium hydroxide, etc.), acetates (sodium acetate, potassium acetate, magnesium acetate, etc.), nitrates (sodium nitrate, potassium nitrate, magnesium nitrate, etc.), sulfates (sodium sulfate, potassium sulfate, magnesium sulfate, etc.), phosphates (sodium phosphate, potassium phosphate, magnesium phosphate, etc.), borates (sodium borate, potassium borate, magnesium borate, etc.), citrates (sodium citrate, potassium citrate, magnesium citrate, etc.), glutamate (sodium glutamate, potassium glutamate, magnesium glutamate, etc.); hydrogen carbonates of alkali metals (sodium hydrogen carbonate, potassium hydrogen carbonate, etc.); percarbonates of alkali metals (sodium percarbonate, potassium percarbonate, etc.); halogen-containing compounds such as fluorides; and polycarboxylic acids.

[0117] The electrolyte of the electrochemical element may be a gel electrolyte obtained by gelling the electrolytic solution with a gelling agent made of a polymer or the like.

[0118] The present invention will be described in detail below based on examples, but the present invention is not limited to these examples.

[0119] (Example 1) Lithium titanate (Li) having an average particle size of 2 μm ４ Ti ５ O １２ , negative electrode active material) and a sulfide-based solid electrolyte (Li6PS ５ Cl) and graphene (conductive additive) were mixed in a mass ratio of 50:41:9 to prepare a negative electrode mixture.

[0120] In addition, LiNbO ３ LiCoO having an average particle size of 5 μm on which a coating layer of ２ (positive electrode active material) and a sulfide-based solid electrolyte (Li6PS ５ Cl) and graphene were mixed in a mass ratio of 65:30.7:4.3 to prepare a positive electrode mixture.

[0121] Next, a sulfide-based solid electrolyte (LiPS) having an average particle size of 0.7 μm was ５ A powder of HCl) was placed in a powder molding die and preforming was performed using a press at a surface pressure of 70 MPa to form a provisionally molded layer of a solid electrolyte layer. Furthermore, the negative electrode mixture was placed on the upper surface of the provisionally molded layer of the solid electrolyte layer and preforming was performed at a surface pressure of 50 MPa, and a provisionally molded layer of a negative electrode was further formed on the provisionally molded layer of the solid electrolyte layer.

[0122] Next, a nickel-made porous metal foam (nickel "Celmet" (registered trademark)) manufactured by Sumitomo Electric Industries, Ltd., cut to a diameter of 7.25 mm (thickness: 1.2 mm, porosity: 98%) was placed on the provisionally molded layer of the negative electrode formed on the provisionally molded layer of the solid electrolyte layer, and pressure molding was performed at a surface pressure of 300 MPa to form an integrated product of the solid electrolyte layer and the negative electrode.

[0123] By the pressure molding, the foamed metal porous body was compressed and embedded in the negative electrode mixture in the provisionally molded layer of the negative electrode (negative electrode mixture), and a negative electrode was obtained in which the porous metal substrate was embedded in the surface layer of the negative electrode mixture layer.

[0124] Furthermore, after the mold was turned upside down, the positive electrode mixture was placed on the upper surface of the solid electrolyte layer in the mold (the surface opposite to the surface having the negative electrode), and preforming was performed at a surface pressure of 50 MPa, thereby forming a provisionally formed layer of the positive electrode on the solid electrolyte layer.

[0125] Next, a cut piece of the same nickel foamed metal porous body used for the negative electrode was placed on the provisionally molded layer of the positive electrode formed on the solid electrolyte layer, and pressure molding was performed at a surface pressure of 1400 MPa to obtain an electrode laminate.

[0126] On the positive electrode side, similarly to the negative electrode, a positive electrode having a porous metal substrate embedded in the surface layer of the positive electrode mixture layer could be obtained.

[0127] In the obtained electrode laminate, the thickness of the negative electrode mixture layer of the negative electrode, the thickness of the porous metal substrate, and the thickness of the portion of the porous metal substrate embedded in the negative electrode mixture layer were 1400 μm, 60 μm (5% of the thickness of the porous metal substrate before use in the negative electrode), and 60 μm (100% of the total thickness of the porous metal substrate), respectively. In addition, the area ratio of the portion of the negative electrode mixture exposed on the surface of the negative electrode was 7%.

[0128] In addition, in the obtained electrode laminate, the thickness of the positive electrode mixture layer of the positive electrode, the thickness of the porous metal substrate, and the thickness of the portion of the porous metal substrate embedded in the positive electrode mixture layer were 800 μm, 60 μm (5% of the thickness of the porous metal substrate before use in the positive electrode), and 60 μm (100% of the total thickness of the porous metal substrate), respectively. In addition, the area ratio of the portion of the positive electrode mixture exposed on the surface of the positive electrode was 7%.

[0129] Comparative Example 1 An electrode stack was produced in the same manner as in Example 1, except that no porous metal substrate was disposed in the positive electrode or negative electrode.

[0130] The electrode laminates of Example 1 and Comparative Example 1 were subjected to impedance measurement by the following method.

[0131] First, using the electrode laminates of Example 1 and Comparative Example 1, coin-type all-solid-state batteries were fabricated in the following manner.

[0132] Flexible graphite sheet "PERMA-FOIL (product name)" manufactured by Toyo Tanso Co., Ltd. (thickness: 0.1 mm, apparent density: 1.1 g / cm ３ One of the sheets was placed on the inner bottom surface of a stainless steel sealing can fitted with a polyphenylene sulfide annular gasket, and the electrode laminate of Example 1 or Comparative Example 1 was placed thereon so that the negative electrode faced the graphite sheet side. The remaining graphite sheet was then placed on the positive electrode of the electrode laminate, and a stainless steel outer can was placed over it. The stainless steel outer can was then placed over it, and the open end of the outer can was then crimped inward to seal, thereby producing a coin-type all-solid-state battery.

[0133] The coin-type all-solid-state batteries were charged at a constant current of 4 mA until the voltage reached 2.6 V, then charged at a constant voltage of 2.6 V until the current reached 0.05 mA, and then discharged at a constant current of 0.01 mA until the voltage reached 1.0 V. Subsequently, charging was performed at a current of 1 mA, and the SOC was adjusted to 10%. Thereafter, each electrode laminate was removed from the coin-type all-solid-state batteries, and the impedance was measured as follows.

[0134] For the electrode laminate of Example 1, both ends of the electrode laminate were sandwiched between two SUS plates (SUS304 plates), and with a load of 0.02 N applied in the thickness direction, AC impedance was measured at 1 kHz with an applied voltage of 10 mV.

[0135] Furthermore, for the electrode laminate of Comparative Example 1, impedance was measured under the following three conditions. (1) Impedance was measured under the same conditions as for the electrode laminate of Example 1, except that the load applied in the thickness direction was changed to 2 N. This is referred to as Comparative Example 1-1. (2) Flexible graphite sheets "PERMA-FOIL (product name)" (thickness: 0.1 mm, apparent density: 1.1 g / cm) manufactured by Toyo Tanso Co., Ltd. were placed between the positive electrode and the negative electrode and the SUS plate, respectively. ３(3) The impedance was measured under the same conditions as for the electrode laminate of Comparative Example 1-1, except that the same foamed metal porous bodies as those used in producing the electrode laminate of Example 1 were placed between the positive electrode and the negative electrode and the SUS plate, respectively, and the impedance was measured under the same conditions as for the electrode laminate of Comparative Example 1-1. This is referred to as Comparative Example 1-3.

[0136] The results of the measurements are shown in Table 1.

[0137]

[0138] As shown in Table 1, the electrode laminate of Example 1, which had an electrode in which a porous metal substrate was embedded in the surface layer of an electrode mixture layer to integrate the porous metal substrate and the electrode mixture layer, and in which the end of the porous metal substrate of the electrode was exposed on the surface, had low impedance even when a small load was applied in the thickness direction. In other words, a good conductive connection was achieved between the electrode and the SUS plate without the SUS plate being pressed hard against the electrode laminate. Therefore, it was found that the electrode laminate of Example 1 could be used to construct an electrochemical element with low internal resistance and excellent characteristics.

[0139] In contrast, the electrode laminate of Comparative Example 1, which has an electrode that does not use a porous metal substrate, had a higher impedance than the electrode laminate of Example 1, even though a larger load was applied in the thickness direction and the SUS plate was pressed strongly against the electrode laminate, in all of Comparative Example 1-1, which did not use a current collector, and Comparative Examples 1-2 and 1-3, in which a graphite sheet or foamed metal porous body that functioned as a current collector was arranged on the electrode surface but was not integrated with the electrode.

[0140] The present invention can be implemented in other forms without departing from the spirit of the present invention. The embodiments disclosed in this application are merely examples, and the present invention is not limited to these embodiments. The scope of the present invention shall be interpreted in accordance with the appended claims rather than the description in the above specification, and all modifications within the scope of the claims are included in the scope of the claims.

[0141] The electrochemical device of the present invention can be used in the same applications as conventionally known electrochemical devices, and the electrode laminate of the present invention can constitute the electrochemical device of the present invention.

[0142] REFERENCE SIGNS LIST 10 Porous metal substrate 11 Electrode mixture 100 Electrochemical element 110 First electrode 111 Electrode mixture layer 112 Porous metal substrate 120 Second electrode 121 Electrode mixture layer 122 Porous metal substrate 130 Separation layer 140 Electrode laminate 150 Outer can 160 Sealing can 170 Gasket

Claims

1. An electrode stack having a first electrode, a second electrode, and an isolating layer interposed therebetween, At least one of the first electrode and the second electrode has an electrode mixture layer and a sheet-like porous metal substrate, At least a portion of the porous metal substrate, including an end portion on the electrode mixture layer side, is embedded in a surface layer portion of the electrode mixture layer and is integrated with the electrode mixture layer, The other end of the porous metal substrate is exposed on the surface of the electrode.

2. 2. The electrode stack according to claim 1, wherein the porous metal substrate is a compressed porous metal foam.

3. 2. The electrode stack according to claim 1, wherein the separator layer is a solid electrolyte layer.

4. 2. The electrode laminate according to claim 1, wherein the thickness of the porous metal substrate is 30% or less of the thickness of the electrode mixture layer.

5. An electrode laminate as described in any of claims 1 to 4, wherein the electrode having an electrode mixture layer and a sheet-like porous metal substrate has an electrode mixture filled in some of the pores at the surface end of the porous metal substrate, and the electrode mixture is exposed on the surface of the electrode.

6. An electrode laminate as described in claim 5, wherein the proportion of the area of ​​the exposed electrode mixture on the surface of the electrode is 50% or less in a planar view.

7. A method for producing the electrode stack of claim 1, comprising the steps of: A first step of preforming an electrode mixture by putting the electrode mixture into a mold and applying pressure thereto; A second step of placing a sheet-shaped porous metal substrate on the electrode mixture preformed in the first step; and a third step of compressing the porous metal substrate toward the electrode mixture, thereby embedding at least a portion of the porous metal substrate, including the end portion on the electrode mixture side, in the electrode mixture, thereby forming an electrode mixture layer integrated with the porous metal substrate.

8. The method for producing an electrode laminate according to claim 7, wherein a foamed porous metal body is used as the porous metal substrate.

9. the separator layer of the electrode stack is a solid electrolyte layer; a preliminary step, prior to the first step, of introducing a solid electrolyte into a mold and pressurizing it to preform it; The method for producing an electrode laminate according to claim 7 , wherein the first step is carried out by placing the electrode mixture on the preformed solid electrolyte.

10. The method for producing an electrode laminate according to claim 7 , wherein in the third step, the thickness of the porous metal substrate is set to 30% or less of the thickness before compression.

11. A method for manufacturing an electrode laminate described in any of claims 7 to 10, wherein in the three steps, the electrode mixture is filled into a portion of the pores at the surface side end of the porous metal substrate, and the electrode mixture is exposed on the surface of the electrode.

12. A method for manufacturing an electrode laminate as described in claim 11, wherein the proportion of the exposed area of ​​the electrode mixture on the surface of the electrode is 50% or less in a planar view.

13. An electrochemical device comprising an exterior body and the electrode laminate according to claim 1 sealed inside the exterior body, The exterior body has a conductive path leading from the inside to the outside, An electrochemical element, characterized in that the porous metal substrate on the surface of the electrode of the electrode laminate is brought into contact with the conductive path, thereby electrically connecting the electrode and the conductive path.

14. 14. The electrochemical element according to claim 13, wherein the porous metal substrate is a compressed porous metal foam.

15. 14. The electrochemical device according to claim 13, wherein the separator layer is a solid electrolyte layer.

16. 14. The electrochemical element according to claim 13, wherein the thickness of the porous metal substrate is 30% or less of the thickness of the electrode mixture layer.

17. An electrochemical element as described in any of claims 13 to 16, wherein the electrode having an electrode mixture layer and a sheet-like porous metal substrate has an electrode mixture filled in some of the pores at the surface end of the porous metal substrate, and the electrode mixture is exposed on the surface of the electrode.

18. An electrochemical element as described in claim 17, wherein the proportion of the area of ​​the exposed electrode mixture on the surface of the electrode is 50% or less in a planar view.