Electrode stack, method for manufacturing the same, and electrochemical element

Abstract

The present invention provides an electrode laminate that can be used in the assembly of electrochemical elements and can reduce internal resistance, a method for manufacturing the same, and an electrochemical element using the electrode laminate. [Solution] The electrode laminate of the present invention comprises a first electrode, a second electrode, and an isolation layer interposed between them, wherein at least one of the first electrode and the second electrode has an electrode mixture layer and a sheet-like porous metal substrate, wherein 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 integrated with the electrode mixture layer, and the other end of the porous metal substrate is exposed on the surface of the electrode. The electrochemical element of the present invention comprises an outer casing having a conductive path to the outside and the electrode laminate of the present invention, wherein the porous metal substrate on the surface of the electrode of the electrode laminate is brought into contact with the conductive path, and the electrode and the conductive path are electrically connected.

Description

Technical Field

[0001] The present invention relates to an electrode laminate that can be used for assembling an electrochemical element and can reduce internal resistance, a method for manufacturing the same, and an electrochemical element using the electrode laminate.

Background Art

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

[0003] Currently, in lithium batteries, particularly lithium-ion batteries, which can meet this requirement, lithium-containing composite oxides such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2) are used as the positive electrode active material, graphite or the like is used as the negative electrode active material, and an organic electrolyte containing an organic solvent and a lithium salt is used as the non-aqueous electrolyte.

[0004] With the further development of the applicable devices of lithium-ion batteries, there is a demand for further extending the lifespan, increasing the capacity, and enhancing the energy density of lithium-ion batteries. At the same time, high reliability of lithium-ion secondary batteries with extended lifespan, increased capacity, and enhanced energy density is also highly demanded.

[0005] However, since the organic electrolyte used in lithium-ion batteries contains an organic solvent that is a flammable substance, when an abnormal situation such as a short circuit occurs in the battery, the organic electrolyte may generate abnormal heat. In addition, with the increasing energy density of recent lithium-ion batteries and the tendency of increasing the amount of organic solvent in the organic electrolyte, higher reliability of lithium-ion batteries is required.

[0006] In such situations, 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 without using an organic solvent instead of the conventional organic solvent-based electrolyte, and have no risk of abnormal heat generation in the solid electrolyte and high reliability.

[0007] In addition, all-solid-state batteries are expected to be maintenance-free batteries that not only have high safety, but also high reliability, high environmental resistance, and long life, and thus can contribute to the development of society and continue to contribute to peace of mind and safety. By providing all-solid-state batteries to society, among the 17 goals of the Sustainable Development Goals (SDGs) established by the United Nations, it can contribute to the achievement of Goal 3 (Ensure healthy lives and promote well-being for all people of all ages), Goal 7 (Ensure access for all people to affordable, reliable, sustainable and modern energy), Goal 11 (Make cities and human settlements inclusive, safe, resilient and sustainable), and Goal 12 (Ensure sustainable consumption and production patterns).

[0008] By the way, in batteries such as all-solid-state batteries, flat-shaped ones called coin-shaped batteries and button-shaped batteries are known. In such flat batteries, an outer package formed by interposing a gasket between an outer can and a sealing can and caulking the open end of the outer can inward is used. And in a battery having an electrode (pellet-shaped electrode) made of a molded body of an electrode mixture containing an active material, such as an all-solid-state battery, usually, the outer can and the sealing can are used as a conductive path leading from the inside to the outside of the battery, and the pellet-shaped electrode is brought into contact with the conductive path, so that the outer can and the sealing can function as a pair of electrode terminals, respectively.

[0009] However, when the pellet-shaped electrode is brought into contact with the conductive path, problems such as insufficient conductive connection between the electrode and the conductive path and an increase in the internal resistance of the battery are likely to occur due to vibration or volume change of the electrode during charge and discharge.

[0010] On the other hand, there are also proposed technologies to reduce internal resistance in batteries having the conductive paths described above. For example, Patent Document 1 discloses an all-solid-state lithium battery in which current collectors made of metal mesh or foamed metal are fixed at multiple locations to at least one of the battery case and sealing plate of the battery, the contact points between the current collectors and electrodes are movable relative to the battery case or sealing plate, and sufficient contact between the current collectors and the positive and negative electrodes of the battery pellets is ensured by the high spring elasticity of the current collectors.

[0011] Furthermore, Patent Document 1 discloses an all-solid-state lithium battery in which, as a different embodiment from the above, the current collector is embedded inside at least one of the pellets of the positive electrode and the negative electrode, thereby creating an electron conduction network within the electrode and improving current collection efficiency. In the all-solid-state lithium battery described in Patent Document 1, these means enable a reduction in internal resistance.

[0012] Furthermore, Patent Document 2 discloses a flat-type all-solid-state battery in which a flexible conductive porous member made of a molded graphite body is placed between a laminate in which a positive electrode, a solid electrolyte layer, and a negative electrode are stacked, and the inner bottom surface of the outer casing or the inner bottom surface of the sealing casing, thereby maintaining good contact between the electrode laminate and the battery container and ensuring excellent conductivity. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Japanese Patent Application Publication No. 10-247516 [Patent Document 2] International Publication No. 2020 / 066323 [Overview of the project] [Problems that the invention aims to solve]

[0014] However, as described in Patent Document 1, when the electrode mixture layer is brought into contact with a current collector made of a highly rigid metal mesh or foamed metal in a movable state, if the force pressing on the contact surface is weak, the electrical contact will not be sufficient, and there is a problem that the internal resistance of the battery will increase. Also, when the current collector is simply embedded inside the electrode mixture layer, a conductive network of the current collector is formed inside the electrode, which can reduce the resistance inside the electrode, but it does not sufficiently reduce the contact resistance between the electrode and the conductive path such as the outer casing or sealed casing.

[0015] On the other hand, as described in Patent Document 2, when a porous molded sheet of graphite is placed between the electrode stack and the battery container, the electrical conductivity between the electrode stack and the battery container can be improved by the pressing force of the sheet. However, there is room for further consideration in order 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 the assembly of an electrochemical element and can reduce internal resistance, a method for manufacturing the same, and an electrochemical element using the electrode laminate. [Means for solving the problem]

[0017] The electrode laminate of the present invention comprises a first electrode, a second electrode, and an isolation layer interposed between them, wherein at least one of the first electrode and the second electrode comprises an electrode mixture layer and a sheet-like porous metal substrate, wherein 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 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 manufactured by a manufacturing method of the present invention, which comprises: a first step of pouring an electrode mixture into a mold and pressurizing it to pre-form it; a second step of placing a sheet-like porous metal substrate on the electrode mixture pre-formed in the first step; and a third step of pressing and compressing the porous metal substrate toward the electrode mixture so that at least a portion of the porous metal substrate, including the end on the electrode mixture side, is embedded in the electrode mixture, thereby forming an electrode mixture layer that is integrated with the porous metal substrate.

[0019] Furthermore, the electrochemical element of the present invention comprises an outer casing and an electrode stack of the present invention sealed inside the outer casing, wherein the outer casing has a conductive path that leads from the inside to the outside, and the porous metal substrate on the surface of the electrodes of the electrode stack is brought into contact with the conductive path, thereby creating electrical conductivity between the electrodes and the conductive path. [Effects of the Invention]

[0020] According to the present invention, it is possible to provide an electrode laminate that can be used in the assembly of an electrochemical element and can reduce internal resistance, a method for manufacturing the same, and an electrochemical element using the electrode laminate. [Brief explanation of the drawing]

[0021] [Figure 1] This is a scanning electron microscope image of the surface (electrode surface) of an example of the electrode stack of the present invention. [Figure 2] This is a schematic cross-sectional view showing an example of the electrochemical element of the present invention. [Modes for carrying out the invention]

[0022] The electrode laminate of the present invention comprises a first electrode, a second electrode, and an isolation layer interposed between them, wherein at least one of the first electrode and the second electrode comprises an electrode mixture layer and a sheet-like porous metal substrate, wherein 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 integrated with the electrode mixture layer, and the other end of the porous metal substrate is exposed on the surface of the electrode.

[0023] In other words, 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) on the electrode mixture layer side of the porous metal substrate, which functions as a current collector, is embedded in the surface layer of the electrode mixture layer. Therefore, the electrode mixture constituting the electrode mixture layer is held in at least a part of the pores of the porous metal substrate, so that the porous metal substrate and the electrode mixture layer are integrated, and as a result the conductivity between the electrode mixture layer and the current collector is very good.

[0024] Furthermore, in the electrode laminate of the present invention, the electrode having an electrode mixture layer and a sheet-like porous metal substrate has an end (end face) of the porous metal substrate opposite to the electrode mixture layer exposed to the surface (electrode surface). Therefore, when an outer casing having a conductive path from the inside to the outside is used, and the electrode laminate of the present invention is housed inside the outer casing to constitute an electrochemical element, the conductivity between the electrode and the conductive path is made very good by bringing the porous metal substrate on the surface of the electrode into contact with the conductive path.

[0025] Through this action, the electrode laminate of the present invention can reduce the internal resistance of the electrochemical element and improve its characteristics. In other words, the electrochemical element of the present invention having the electrode laminate of the present invention has low internal resistance and excellent characteristics due to the aforementioned action of the electrode laminate.

[0026] In the electrode laminate of the present invention, either the first electrode or the second electrode may have the above configuration, namely, an electrode mixture layer and a sheet-like porous metal substrate, wherein 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 integrated with the electrode mixture layer, and the other end of the porous metal substrate is exposed on the surface of the electrode. This configuration can reduce the internal resistance of the electrochemical element. However, from the viewpoint of further reducing internal resistance and constructing an electrochemical element with superior characteristics, it is preferable that both the first electrode and the second electrode have the above configuration.

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

[0028] <Electrode Laminate> The electrode stack comprises a first electrode, a second electrode, and an isolation layer interposed between them.

[0029] When an electrochemical element using an electrode stack is a battery or a lithium-ion capacitor, one of the first electrode and the second electrode is the positive electrode and the other is the negative electrode. Furthermore, when an electrochemical element using an electrode stack is an electric double-layer capacitor, the first electrode and the second electrode can be electrodes with the same configuration.

[0030] Furthermore, as described above, 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 integrated with the electrode mixture layer, while the other end of the porous metal substrate is exposed on the surface of the electrode.

[0031] In an electrode stack used in a battery, if the electrode having the above configuration is the 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 configuration is the positive electrode of a primary battery, the positive electrode active material can be the same as the positive electrode active material conventionally known for use in non-aqueous electrolyte primary batteries, alkaline batteries, manganese batteries, etc. Specifically, for example, manganese dioxide, lithium-containing manganese oxide [for example, LiMn3O6, or composite oxides having the same crystal structure as manganese dioxide (β-type, γ-type, or a structure in which β-type and γ-type are mixed, etc.) and having 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], Li a Ti 5 / 3 Examples include lithium-containing composite oxides such as O4 (4 / 3 ≤ a < 7 / 3); vanadium oxide; niobium oxide; titanium oxide; sulfides such as iron disulfide; graphite fluoride; silver sulfides such as Ag2S; and nickel oxides such as NiO2.

[0033] Furthermore, when the electrode having the above configuration is the positive electrode of a secondary battery, the same positive electrode active material as that used in conventionally known non-aqueous electrolyte secondary batteries, alkaline secondary batteries, etc., can be used. Specifically, Li 1-x M r Mn 2-rSpinel-type lithium manganese composite oxide represented by O4 (where 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; 0 ≦ x ≦ 1, 0 ≦ r ≦ 1), Li r Mn (1-s-t) Ni s M t O (2-u) F v (where 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; 0 ≦ r ≦ 1.2, 0 < s < 0.5, 0 ≦ t ≦ 0.5, u + v < 1, -0.1 ≦ u ≦ 0.2, 0 ≦ v ≦ 0.1) Layered compound represented by Li 1-x Co 1-r M r Lithium cobalt composite oxide represented by O2 (where 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; 0 ≦ x ≦ 1, 0 ≦ r ≦ 0.5), Li 1-x Ni 1-r M r Lithium nickel composite oxide represented by O2 (where 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; 0 ≦ x ≦ 1, 0 ≦ r ≦ 0.5), Li 1+s-x M<00000?19>N r PO4F s (where 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; 0 ≦ x ≦ 1, 0 ≦ r ≦ 0.5, 0 ≦ s ≦ 1) Olivine-type composite oxide represented by Li 2-x M 1-r N rExamples include pyrophosphate compounds represented by P2O7 (where 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, with 0≦x≦2 and 0≦r≦0.5), nickel hydroxide, silver oxide, etc. Only one of these may be used, or two or more may be used in combination.

[0034] When the electrochemical element 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, more preferably 10 μm or less, and more preferably 8 μm or less. The positive electrode active material may be primary particles or secondary particles formed by aggregation of primary particles. Using a positive electrode active material with an average particle size within the above range allows for a larger interface with the solid electrolyte contained in the positive electrode, thereby improving the output characteristics of the battery.

[0035] In this specification, the average particle diameter of various particles (such as positive electrode active material and solid electrolyte) is the 50% diameter value in the volume-based integrated fraction when determining the integrated volume from the smallest particles using a particle size distribution analyzer (such as the Microtrac particle size distribution analyzer "HRA9320" manufactured by Nikkiso Co., Ltd.). 50 ) means.

[0036] In the case of an all-solid-state secondary battery, it is preferable that the positive electrode active material has a reaction-inhibiting layer on its surface to suppress the 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 within the electrode mixture layer (positive electrode mixture layer), the solid electrolyte may oxidize and form a resistive layer, potentially reducing the ionic conductivity within the electrode mixture layer. By providing a reaction-inhibiting layer on the surface of the positive electrode active material to suppress the reaction with the solid electrolyte, direct contact between the positive electrode active material and the solid electrolyte can be prevented, thereby suppressing the reduction in ionic conductivity within the electrode mixture layer due to oxidation of the solid electrolyte.

[0038] The reaction suppression layer should be composed of a material that has ionic conductivity and can suppress the reaction between the positive electrode active material and the solid electrolyte. Examples of materials that can constitute 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, Nb-containing oxides such as LiNbO3, Li3PO4, Li3BO3, Li4SiO4, Li4GeO4, LiTiO3, LiZrO3, and Li2WO4. The reaction suppression layer may contain only one of these oxides, or two or more, and furthermore, multiple of these oxides may form a composite compound. Among these oxides, it is preferable to use an Nb-containing oxide, and more preferable to use LiNbO3.

[0039] The reaction-inhibiting 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 positive electrode active material. Within this range, the reaction between the positive electrode active material and the solid electrolyte can be effectively suppressed.

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

[0041] From the viewpoint of increasing the energy density of the electrochemical element, the content of the positive electrode active material in the positive electrode mixture is preferably 60 to 85% by mass.

[0042] The positive electrode mixture may contain a conductive additive. Specific examples include carbon materials such as graphite (natural graphite, artificial graphite), graphene, carbon black, carbon nanofibers, and carbon nanotubes. However, if Ag2S is used as the active material, conductive Ag is generated during the discharge reaction, so a conductive additive does not need to be included. When a conductive additive is included in the positive electrode mixture, its content 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, based on the content of 100 parts by mass of the positive electrode active material.

[0043] Furthermore, a binder can be included in the positive electrode mixture. Specific examples include fluororesins such as polyvinylidene fluoride (PVDF). However, if good moldability can be ensured in forming the electrode mixture layer (positive electrode mixture layer) without using a binder, for example, when the positive electrode mixture contains a sulfide-based solid electrolyte (details will be discussed later), then the positive electrode mixture does not need to contain a binder.

[0044] In the positive electrode mixture, if a binder is required, its content is preferably 15% by mass or less, and more preferably 0.5% by mass or more. On the other hand, in the positive electrode mixture, if moldability can be obtained without the need for a binder, its content 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 included).

[0045] When the electrochemical element is an all-solid-state battery (all-solid-state primary battery, all-solid-state secondary battery), it is preferable to include a solid electrolyte in the positive electrode mixture.

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

[0047] Examples of sulfide-based solid electrolytes include particles such as Li2S-P2S5, Li2S-SiS2, Li2S-P2S5-GeS2, and Li2S-B2S3 glass, as well as thio-LISICON type electrolytes, which have recently attracted attention for their high Li ion conductivity. 10 GeP2S 12 Li 9.54 Si 1.74 P 1.44 S 11.7 Cl 0.3 Examples include the general formula Li 12-12a-b+c+6d-e M 1 3+a-b-c-dM 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), and those having an all-dielectric type crystal structure exemplified later can also be used.)

[0048] Examples of the hydride-based solid electrolyte include, for example, LiBH4, a solid solution of LiBH4 and the following alkali metal compound (for example, those having a molar ratio of LiBH4 to the alkali metal compound of 1:1 to 20:1), and the like. Examples of the alkali metal compound in the solid solution include at least one selected from the group consisting of lithium halide (LiI, LiBr, LiF, LiCl, etc.), rubidium halide (RbI, RbBr, RbF, RbCl, etc.), cesium halide (CsI, CsBr, CsF, CsCl, etc.), lithium amide, rubidium amide, and cesium amide.)

[0049] Examples of the halide-based solid electrolyte include, for example, monoclinic LiAlCl4, defective spinel-type or layered LiInBr4, monoclinic Li 6-3m Y m X6 (where 0 < m < 2 and X = Cl or Br), etc., and in addition, for example, those known from WO2020 / 070958 and WO2020 / 070955 can also be used.)

[0050] Examples of the oxide-based solid electrolyte include, for example, garnet-type Li7La3Zr2O 12 、NASICON-type Li 1+O Al<00Ti 2-O (PO4)3, Li 1+p Al 1+p Ge 2-p (PO4)3, perovskite-type Li 3q La 2 / 3-q Examples include TiO3.

[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 crystal structure are even more preferred due to their higher lithium ion conductivity and chemical stability.

[0052] As sulfide-based solid electrolytes having an argyrodite-type crystal structure, those represented by the following general composition formula (1) or (2), such as Li6PS5Cl, are particularly preferred.

[0053] Li 7-x+y PS 6-x Cl x+y (1)

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

[0055] Li 7-a PS 6-a Cl b Br c (2)

[0056] In the above general composition formula (2), a = b + c, 0 <a≦1.8、0.1≦b / c≦10.0である。

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

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

[0059] In an electrode stack used in a battery, if the electrode having the above configuration is the 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 negative electrode active materials include carbon materials such as graphite, lithium titanium oxide (such as lithium titanate), elements such as Si and Sn, elements in elemental form, compounds (such as oxides), and alloys thereof. In addition, lithium metal and lithium alloys (such as lithium-aluminum alloy and lithium-indium alloy) can also be used as negative electrode active materials.

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

[0062] The negative electrode mixture may contain a conductive additive. Specific examples include the same conductive additives mentioned earlier as those that can be included in the positive electrode mixture. The content of the conductive additive in the negative electrode mixture is preferably 10 to 30 parts by mass, based on a negative electrode active material content of 100 parts by mass.

[0063] Furthermore, a binder can be included in the negative electrode mixture. Specific examples include the same binders mentioned earlier that can be included in the positive electrode mixture. However, if good moldability can be ensured in forming the electrode mixture layer (negative electrode mixture layer) without using a binder, such as when the negative electrode mixture contains a sulfide-based solid electrolyte (as described later), then the negative electrode mixture does not need to contain a binder.

[0064] In the negative electrode mixture, if a binder is required, its content is preferably 15% by mass or less, and more preferably 0.5% by mass or more. On the other hand, in the negative electrode mixture, if moldability can be obtained without the need for a binder, its content 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 included).

[0065] When the electrochemical element is an all-solid-state battery, it is preferable to include a solid electrolyte in the negative electrode mixture. Specific examples include the same solid electrolytes exemplified above that can be included in the positive electrode mixture. Among the exemplified solid electrolytes, sulfide-based solid electrolytes are preferred because they have high lithium-ion conductivity and enhance the moldability of the negative electrode mixture. More preferably, sulfide-based solid electrolytes having an argyrodite crystal structure are used, and even more preferably, those represented by the general composition formula (1) or (2) are used.

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

[0067] From the viewpoint of further enhancing ionic conductivity within the negative electrode and improving the output characteristics of the electrochemical element, the solid electrolyte content in the negative electrode mixture is preferably 30 parts by mass or more, and more preferably 35 parts by mass or more, when the negative electrode active material content is 100 parts by mass. However, if the amount of solid electrolyte in the negative electrode mixture is too high, the amount of other components will decrease, and the effects of those components may be reduced. Therefore, the solid electrolyte content in the negative electrode mixture is preferably 130 parts by mass or less, and more preferably 110 parts by mass or less, when the negative electrode active material content is 100 parts by mass.

[0068] When the electrochemical element using the electrode stack is an electric double-layer capacitor, the electrode mixture layer of the electrode having the above configuration can be formed by 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 using the electrode stack is a lithium-ion capacitor, the electrode composite layer of the electrode having the above configuration can be formed by an electrode composite having the same configuration as the electrode composite for the electrode of an electric double-layer capacitor if the electrode is a positive electrode, and by an electrode composite having the same configuration as the negative electrode composite if the electrode is a negative electrode.

[0070] In electrodes having the above configuration, it is preferable to use a foamed metal porous material for the porous metal substrate. A specific example of a foamed metal porous material is "Cellmet®" from Sumitomo Electric Industries, Ltd. Such porous metal substrates are usually compressed and their thickness decreases when electrodes are manufactured together with the electrode mixture, so the thickness before use in the electrode (electrode stack) is greater than the aforementioned 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 it is 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 manufacture of the electrode stack described later, and its thickness becomes the values ​​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, in order to facilitate the filling of the pores in the porous metal substrate with the electrode mixture during the process of pressurizing the porous metal substrate and the electrode mixture, and to allow the porous metal substrate and the electrode mixture layer to easily integrate. On the other hand, in order to increase conductivity by keeping the amount of substrate above a certain level, the porosity is preferably 99.5% or less, more preferably 99% or less, and particularly preferably 98.5% or less.

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

[0073] In the electrode with the above configuration, the thickness of the portion of the porous metal substrate embedded in the electrode mixture layer is preferably 10% or more, and more preferably 20% or more, of the total thickness of the porous metal substrate (the total thickness of the porous metal substrate, including the thickness of the portion where the electrode mixture layer coexists; unless otherwise specified, the same applies hereinafter regarding 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 the electrode configuration described above, in order to reduce the resistance when in contact with the conductive path in the outer casing of the electrochemical element, it is desirable that the end of the porous metal substrate opposite to the electrode mixture layer (hereinafter sometimes referred to as the surface end) is not embedded in the electrode mixture layer, and that the end of the electrode (the electrode surface) is composed solely of the porous metal substrate. That is, when the porous metal substrate is compressed in the thickness direction during the manufacturing of the electrode laminate described later, it is desirable that the voids at the surface end of the porous metal substrate are crushed and eliminated, leaving only the porous metal substrate exposed on the electrode surface. However, some of the voids at the surface end of the porous metal substrate may not be crushed and may remain as voids, or the electrode mixture may be filled into them, and as long as it does not significantly affect the contact resistance with the conductive path, some of the electrode mixture may be exposed on the electrode surface along with the surface end of the porous metal substrate. In other words, as long as the surface end of the porous metal substrate can be exposed on the electrode surface, the entire porous metal substrate (100% of the thickness of the porous metal substrate) may be embedded in the surface layer of the electrode mixture layer. By ensuring that the electrode mixture fills the pores of the porous metal substrate all the way to the electrode surface, the integration of the electrode mixture and the porous metal substrate can be made more reliable.

[0075] Figure 1 shows a scanning electron microscope (SEM) image of the surface of an example of the electrode stack of the present invention. On the surface of the electrode stack shown in Figure 1 (the electrode surface), the edges of the porous metal substrate 10 of the electrode having the above-described configuration are exposed, but a portion of the electrode mixture 11 is also exposed on the electrode surface by entering into voids present at the edges of the porous metal substrate.

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

[0077] In the electrode with the above configuration, when embedding at least a portion of the porous metal substrate 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, more preferably 2% or more, and particularly preferably 3% or more, of the total thickness of the electrode mixture layer (including the thickness of the portion coexisting with the porous metal substrate; hereinafter, "thickness of the electrode mixture layer" means "total thickness of the electrode mixture layer" unless otherwise specified). Furthermore, from the viewpoint of improving the filling properties of the electrode mixture layer in the electrode, the thickness of the porous metal substrate is preferably 30% or less, more preferably 20% or less, and particularly preferably 10% or less, of the thickness of the electrode mixture layer.

[0078] In the electrode configuration described above, 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. Furthermore, 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] In the electrode laminate, the thickness of the porous metal substrate and the thickness of the electrode mixture layer are determined by the maximum width in the thickness direction of the region where the porous metal substrate is visible and the region where the electrode mixture is visible, respectively, in an image obtained by observing the cross-section of the electrode in the thickness direction using SEM at a magnification of 50 to 1000 times. Furthermore, the thickness of the portion of the porous metal substrate embedded in the electrode mixture layer is determined by the maximum width in the thickness direction of the overlapping region of the porous metal substrate and the electrode mixture (the values ​​in the examples described later were obtained by these methods).

[0080] Furthermore, the proportion (area ratio) of the electrode mixture exposed on the electrode surface is determined by the ratio (A / B) of the total area of ​​the exposed electrode mixture (A) to the total area of ​​the electrode (B) in images of the electrode surface observed by SEM at a magnification of 50 to 200 times (the values ​​in the examples described later were obtained by this method).

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

[0082] Specific examples of the solid electrolyte constituting the solid electrolyte layer include the same solid electrolytes as those previously exemplified as those that can be included in the positive electrode mixture. Among the solid electrolytes exemplified above, sulfide-based solid electrolytes are preferred because they have high lithium ion conductivity and the function of improving the moldability of the negative electrode mixture. More preferably, sulfide-based solid electrolytes having an argyrodite-type crystal structure are used, and even more preferably, those represented by the general composition formula (1) or the general composition formula (2) are used.

[0083] The solid electrolyte layer may have a porous material, 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 utilize electrolytes containing solvents, a separator is used as an isolation layer interposed between the first electrode and the second electrode.

[0086] As a separator, one that has sufficient strength and can retain a large amount of electrolyte is preferable. From this viewpoint, microporous films or nonwoven fabrics containing polyethylene, polypropylene, or ethylene-propylene copolymer, with a thickness of 10 to 50 μm and an opening ratio of 30 to 70%, are preferred.

[0087] The electrode stack can be manufactured by a manufacturing method comprising the following steps 1 to 3.

[0088] In the first step, the electrode mixture is poured into a mold and pre-formed under pressure. The surface pressure for pre-formation in the first step is preferably, for example, 30 to 500 MPa.

[0089] In the next second step, a porous metal substrate is placed on the electrode mixture that was pre-formed in the first step, and in the following third step, the porous metal substrate is pressed and compressed toward the electrode mixture. This pressing in the third step causes at least a portion of the porous metal substrate, including the end on the electrode mixture side, to be embedded in the electrode mixture, thereby forming an electrode mixture layer 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. From the viewpoint of more reliably forming the porous metal substrate and the electrode mixture layer, it is preferable that the thickness of the porous metal substrate after compression be 30% or less of the thickness before compression, more preferably 20% or less, and particularly preferable 10% or less. Furthermore, from the viewpoint of retaining a certain amount of electrode mixture in the voids of the porous metal substrate and increasing the bonding strength between the porous metal substrate and the electrode mixture layer, it is preferable that the thickness of the porous metal substrate after compression in the third step be 1% or more of the thickness before compression, and more preferably 2% or more.

[0091] In the third step, the surface pressure during pressurization is preferably 800 MPa or higher, more preferably 1000 MPa or higher, and particularly preferably 1200 MPa or higher, in order to sufficiently increase the density of the electrode mixture layer by compression molding the electrode mixture. There is no specific upper limit for the surface pressure during pressurization in the third step, but in a typical pressurization device, the upper limit is usually around 2000 MPa.

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

[0093] Furthermore, if the surface pressure during pressurization in the third step becomes high, cracks may occur when the porous metal substrate is compressed. However, even if it is cut and fragments are generated, if the ends of these fragments are exposed on the electrode surface, it can contribute to reducing contact resistance.

[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. Alternatively, the electrode placed on one side of the separator can be an electrode other than the one configured above (such as an electrode consisting only of a molded electrode mixture without a current collector, or an electrode using 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 can be prepared, placed on both sides of the solid electrolyte layer, and pressurized as needed to form an electrode laminate. Alternatively, the electrode placed on one side of the solid electrolyte layer can be an electrode other than the one described above (such as an electrode consisting only of a molded electrode mixture without a current collector, or an electrode using metal foil or the like as a current collector).

[0096] Furthermore, when manufacturing an electrode laminate having a solid electrolyte layer, a preliminary step can be provided before the first step in which the solid electrolyte is placed in a mold and pressurized to pre-form it. The electrode mixture can then be placed on the solid electrolyte pre-formed in this preliminary step, and the first step can be carried out thereafter.

[0097] The surface pressure during pre-forming in the preliminary process is preferably, for example, 30 to 120 MPa.

[0098] Furthermore, an electrode laminate having electrodes with the above configuration on both sides of a solid electrolyte layer can also be manufactured by sequentially performing the first, second, and third steps on the other side of a solid electrolyte layer that has electrodes with the above configuration formed on one side, starting from the preliminary steps.

[0099] <Electrochemical elements> The electrochemical element of the present invention comprises an outer casing and an 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 electrodes of the electrode laminate is brought into contact with the conductive path, thereby creating electrical conductivity between the electrodes and the conductive path.

[0100] Figure 2 shows a schematic cross-sectional view of an example of the electrochemical element of the present invention. The electrochemical element 100 shown in Figure 2 has an electrode laminate 140 having a first electrode 110, a second electrode 120, and an isolation layer 130 interposed between them, which is sealed inside an outer casing formed of a metal outer casing 150, a metal sealing casing 160, and a resin gasket 170 interposed between them. The sealing casing

[0101] If the electrode stack 140 has a solid electrolyte layer as an isolation layer 130, for example, only the electrode stack 140 is sealed inside the outer casing. On the other hand, if the electrode stack 140 has a separator as an isolation layer 130, the outer casing contains an electrolyte (not shown) along with the electrode stack 140.

[0102] The first electrode 110 has an electrode mixture layer 111 and a porous metal substrate 112, and 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 area where the porous metal substrate 112 is located 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 opposite to the electrode mixture layer 111 side (the lower end in Figure 2) is exposed on the surface. 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. In other words, the entire area where the porous metal substrate 122 is located 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 opposite to the electrode mixture layer 121 side (the upper end in Figure 2) is exposed on the surface. 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] In the electrochemical element 100 shown in Figure 2, the metal outer casing 150 forms a conductive path on the first electrode 110 side. The end of the porous metal substrate 112 exposed on the surface of the first electrode 110 comes into contact with the inner surface of the outer casing 150, thereby creating electrical contact between the first electrode 110 and the outer casing 150 (the conductive path formed by the outer casing 150). The outer surface of the outer casing 150 serves as an external terminal for electrically connecting the electrochemical element to external equipment.

[0105] Furthermore, in the electrochemical element 100 shown in Figure 2, the metal sealing can 160 forms a conductive path on the second electrode 120 side, and the end of the porous metal substrate 122 exposed on the surface of the second electrode 120 comes into contact with the inner surface of the sealing can 160, thereby creating electrical contact between the second electrode 120 and the sealing can 160 (the conductive path formed by the sealing can 160). The outer surface of the sealing can 160 then serves as an external terminal for electrically connecting the electrochemical element to external equipment.

[0106] The casing of the electrochemical element may consist of a case having an outer can and a sealed can, as shown in Figure 2. In other words, an electrochemical element with such a case as its casing will be coin-shaped (button-shaped).

[0107] In cases where the casing of an electrochemical element has an outer can and a sealing can, as shown in Figure 2, examples include cases where the outer can and the sealing can are crimped together via a gasket, and cases where the outer can and the sealing can are bonded together with resin.

[0108] Stainless steel can be used for the outer casing and sealing cans. For the gasket material, polypropylene and nylon can be used. Furthermore, if heat resistance is required due to the application of the electrochemical element, heat-resistant resins with melting points exceeding 240°C, such as fluororesins like tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), polyphenylene ether (PEE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), and polyetheretherketone (PEEK), can also be used. Additionally, when the electrochemical element is applied to an application requiring heat resistance, a glass hermetic seal can be used for sealing.

[0109] Furthermore, the casing of the electrochemical element is not limited to having an outer can and a sealed can, as long as it has a conductive path that leads from the inside to the outside of the casing, and the porous metal substrate on the surface of the electrode of the electrode stack is in contact with the conductive path to enable electrical conductivity between the electrode and the conductive path. For example, a ceramic case in which a conductive path made of metals such as gold, platinum, silver, palladium, copper, nickel, and cobalt, or their alloys, is provided to penetrate through the constituent material can also be used as the casing of the electrochemical element.

[0110] The shape of the outer casing of the electrochemical element in plan view may be circular, or it may be a polygon such as a square or rectangle.

[0111] In the case of an electrochemical element having an electrode stack with a separator as an isolation layer, an electrolyte is used as described above. Typically, a liquid electrolyte (non-aqueous electrolyte or aqueous electrolyte) having a non-aqueous or aqueous solvent is used as the electrolyte. The non-aqueous electrolyte is prepared by dissolving an electrolyte salt such as a lithium salt in an organic solvent. The organic solvent is not particularly limited, but examples include linear 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 linear esters and cyclic esters. Mixed solvents of linear esters and cyclic esters are particularly suitable.

[0112] For example, when the electrochemical element is a battery or lithium-ion capacitor, the electrolyte salts to be dissolved in the organic solvent include LiPF6, LiBF4, LiAsF6, LiSbF6, LiCF3SO3, LiC4F9SO3, LiCF3CO2, Li2C2F4(SO3)2, and LiC n F 2n+1 SO3 (n≧2), LiN(RfSO2)(Rf'SO2), LiC(RfSO2)3, LiN(RfOSO2)2 (where Rf and Rf' are fluoroalkyl groups) can be used individually or in combination of two or more. In addition, for the non-aqueous electrolyte in the case of an electric double-layer capacitor, (C2H5)4NBF4, (C2H5)4PBF4, etc., are used as the electrolyte salts.

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

[0114] Furthermore, as aqueous electrolytes, alkaline aqueous solutions (alkaline electrolytes) consisting of aqueous solutions of alkali metal hydroxides such as potassium hydroxide, sodium hydroxide, and lithium hydroxide, or aqueous solutions with a pH in the range of 3 to 12 are used.

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

[0116] Furthermore, aqueous solutions with a pH in the range of 3 to 12 include solutions obtained 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.), glutamates (sodium glutamate, potassium glutamate, magnesium glutamate, etc.); alkali metal bicarbonates (sodium bicarbonate, potassium bicarbonate, etc.); alkali metal percarbonates (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-like electrolyte obtained by gelling the aforementioned electrolyte with a gelling agent such as a polymer. [Examples]

[0118] The present invention will be described in detail below based on examples. However, the following examples are not intended to limit the present invention.

[0119] (Example 1) Lithium titanate (Li4Ti5O) with an average particle size of 2 μm 12 A negative electrode mixture was prepared by mixing a negative electrode active material, a sulfide-based solid electrolyte (Li6PS5Cl) with an average particle size of 0.7 μm, and graphene (conductive additive) in a mass ratio of 50:41:9.

[0120] Furthermore, a positive electrode mixture was prepared by mixing LiCoO2 (positive electrode active material) with an average particle size of 5 μm and a LiNbO3 coating layer formed on its surface, a sulfide-based solid electrolyte (Li6PS5Cl) with an average particle size of 0.7 μm, and graphene in a mass ratio of 65:30.7:4.3.

[0121] Next, a sulfide-based solid electrolyte (Li6PS5Cl) powder with an average particle size of 0.7 μm was placed in a powder molding die, and pre-molding was performed using a press machine at a surface pressure of 70 MPa to form a preliminary layer of the solid electrolyte. Furthermore, the anode mixture was placed on the upper surface of the preliminary layer of the solid electrolyte and pre-molded at a surface pressure of 50 MPa to form another preliminary layer of the anode on top of the preliminary layer of the solid electrolyte.

[0122] Next, a piece of nickel-based foamed metal porous material [Nickel "Cellmet" (registered trademark)] from Sumitomo Electric Industries, Ltd., cut to a diameter of 7.25 mm (thickness: 1.2 mm, porosity: 98%), was placed on the temporary molding layer of the negative electrode formed on the temporary molding layer of the solid electrolyte layer. Pressure molding was then performed at a surface pressure of 300 MPa to form an integrated solid electrolyte layer and negative electrode.

[0123] Through the aforementioned pressure molding, the foamed porous metal body was compressed and embedded in the negative electrode mixture in the pre-formed 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 inverting the mold, the positive electrode mixture was placed on the upper surface of the solid electrolyte layer inside the mold (the side opposite to the side with the negative electrode) and pre-molded with a surface pressure of 50 MPa to form a temporary positive electrode layer on top of the solid electrolyte layer.

[0125] Next, a piece of the same nickel-based foamed metal porous material used for the negative electrode was placed on top of the pre-formed positive electrode layer 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, similar to the negative electrode, a positive electrode was obtained in which a porous metal substrate was embedded in the surface layer of the positive electrode mixture layer.

[0127] In the obtained electrode laminate, the thickness of the negative electrode mixture layer, 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 as a negative electrode), and 60 μm (100% of the total thickness of the porous metal substrate), respectively. Furthermore, the area ratio of the portion of the negative electrode mixture exposed on the surface of the negative electrode was 7%.

[0128] Furthermore, in the obtained electrode laminate, the thickness of the positive electrode mixture layer, 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 laminate was fabricated in the same manner as in Example 1, except that porous metal substrates were not placed at the positive and negative electrodes.

[0130] The electrode stacks of Example 1 and Comparative Example 1 were subjected to impedance measurements using the following method.

[0131] First, coin-type all-solid-state batteries were fabricated using the electrode stacks of Example 1 and Comparative Example 1 according to the following procedure.

[0132] Flexible graphite sheet "PERMA-FOIL" (product name) manufactured by Toyo Tanso Co., Ltd. (thickness: 0.1 mm, apparent density: 1.1 g / cm³)3 Two pieces were prepared by punching out the same size as the molded body, and one of them was placed on the inner bottom surface of a stainless steel sealing can fitted with a polyphenylene sulfide annular gasket. On top of that, the electrode stack of Example 1 or Comparative Example 1 was placed with the negative electrode facing the graphite sheet side. Furthermore, the remaining graphite sheet was placed on the positive electrode of the electrode stack, and after covering it with a stainless steel outer can, the open end of the outer can was crimped inward to seal it, thereby manufacturing a coin-type all-solid-state battery.

[0133] A coin-type all-solid-state battery was charged with a constant current of 4mA until the voltage reached 2.6V, then charged with a constant voltage of 2.6V until the current reached 0.05mA, and finally discharged with a constant current of 0.01mA until the voltage reached 1.0V. Subsequently, it was charged with a current of 1mA and adjusted to achieve a State of Charge (SOC) of 10%. After that, each electrode stack was removed from the coin-type all-solid-state battery, and its impedance was measured as follows.

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

[0135] Furthermore, the impedance of the electrode laminate of Comparative Example 1 was measured under the following three conditions. (1) The impedance was measured under the same conditions as the electrode laminate in Example 1, except that the load applied in the thickness direction was changed to 2N. This is referred to as Comparative Example 1-1. (2) Between the positive electrode and the negative electrode and the SUS plate, a flexible graphite sheet "PERMA-FOIL" (product name) manufactured by Toyo Tanso Co., Ltd. (thickness: 0.1 mm, apparent density: 1.1 g / cm³) is placed. 3 The impedance was measured under the same conditions as the electrode stack of Comparative Example 1-1, except that the ) was placed and the measurement was performed. This is designated as Comparative Example 1-2. (3) The impedance was measured under the same conditions as the electrode laminate of Comparative Example 1-1, except that the same foamed metal porous material used in the fabrication of the electrode laminate of Example 1 was placed between the positive electrode and the negative electrode and the SUS plate. This was designated as Comparative Example 1-3.

[0136] The measurement results are shown in Table 1.

[0137] [Table 1]

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

[0139] In contrast, the electrode laminates of Comparative Example 1, which had electrodes that did not use a porous metal substrate, showed higher impedance than the electrode laminate of Example 1, even when the load applied in the thickness direction was increased and the SUS plate was strongly pressed towards the electrode laminate. This was true for Comparative Example 1-1, which did not use a current collector, and for Comparative Examples 1-2 and 1-3, which had graphite sheets or foamed porous metal materials that functioned as current collectors placed on the electrode surface but were not integrated with the electrodes.

[0140] The present invention can also be implemented in forms other than those described herein, without departing from its spirit. The embodiments disclosed herein are examples, and the present invention is not limited to these embodiments. The scope of the present invention shall be interpreted in accordance with the claims attached, which take precedence over the description herein, and all modifications within the scope equivalent to the claims are included in the claims. [Industrial applicability]

[0141] The electrochemical element of the present invention can be applied to the same applications as conventionally known electrochemical elements. Furthermore, the electrode laminate of the present invention can constitute the electrochemical element of the present invention. [Explanation of Symbols]

[0142] 10 Porous metal substrate 11 Electrode mixture 100 Electrochemical Elements 110 1st electrode 111 Electrode mixture layer 112 Porous metal substrate 120 2nd electrode 121 Electrode mixture layer 122 Porous metal substrate 130 Isolation layer 140 electrode stack 150 (outer can) 160 Sealed cans 170 Gasket

Claims

1. An electrode laminate having a first electrode, a second electrode, and an isolation layer interposed between them, At least one of the first electrode and the second electrode has an electrode mixture layer and a sheet-like porous metal substrate. The porous metal substrate is a compressed foamed porous metal body, and at least a portion of it, including the end on the electrode mixture layer side, is embedded in the surface layer of the electrode mixture layer and integrated with the electrode mixture layer. The other end of the porous metal substrate is exposed to the surface of the electrode. The electrode having an electrode mixture layer and a sheet-like porous metal substrate is characterized in that the electrode mixture fills a portion of the voids at the surface edge of the porous metal substrate, the electrode mixture is exposed on the surface of the electrode, and the proportion of the exposed area of ​​the electrode mixture on the surface of the electrode is 50% or less in a plan view.

2. The electrode laminate according to claim 1, wherein the isolation layer is a solid electrolyte layer.

3. 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.

4. A method for manufacturing an electrode stack according to claim 1, The first step involves pouring the electrode mixture into a mold and applying pressure to pre-form it, A second step involves placing a sheet-like porous metal substrate on the electrode mixture pre-formed in the first step, A method for manufacturing an electrode laminate, comprising a third step of pressurizing and compressing the porous metal substrate toward the electrode mixture, thereby embedding at least a portion of the porous metal substrate, including the end on the electrode mixture side, into the electrode mixture, and forming an electrode mixture layer integrated with the porous metal substrate.

5. The isolation layer of the electrode stack is a solid electrolyte layer, Prior to the first step, there is a preliminary step in which a solid electrolyte is poured into a mold and pressurized to pre-form it. The method for manufacturing an electrode laminate according to claim 4, wherein the electrode mixture is placed on the pre-formed solid electrolyte and the first step is carried out.

6. The method for manufacturing an electrode laminate according to claim 4, wherein in the third step, the thickness of the porous metal substrate is 30% or less of the thickness before compression.

7. An electrochemical element comprising an outer casing and an electrode laminate according to claim 1 sealed inside the outer casing, The aforementioned exterior body has a conductive path that leads 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 stack is brought into contact with the conductive path, thereby creating electrical conductivity between the electrode and the conductive path.

8. The electrochemical element according to claim 7, wherein the isolation layer is a solid electrolyte layer.

9. The electrochemical element according to claim 7, wherein the thickness of the porous metal substrate is 30% or less of the thickness of the electrode mixture layer.

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