Electrode and secondary battery using the same

Abstract

The problem to be solved by the present invention is to improve the adhesion between the electrode composite and the solid electrolyte, thereby suppressing the electrodeposition of lithium. To solve the above problem, the present invention provides an electrode comprising: a planar electrode current collector composed of a porous metal body; an electrode composite layer filling the pores of the porous metal body; and a solid electrolyte layer filling the pores of the porous metal body. The electrode composite layer is formed on one side of the electrode current collector, and the solid electrolyte layer is formed on the other side. The electrode composite layer and the solid electrolyte layer are laminated into a planar shape within the pores of the porous metal body.

Description

Technical Field

[0001] The present invention relates to an electrode and a secondary battery using the same. Background Art

[0002] Lithium-ion secondary batteries have been widely used as high-energy-density secondary batteries. Solid-state batteries, where the electrolyte is solid, have a battery structure in which the solid electrolyte is located between the positive and negative electrodes. Multiple such cells are stacked to form a solid-state lithium-ion secondary battery.

[0003] In solid-state batteries, to maintain ionic conductivity of lithium ions, the electrode composite containing the positive or negative active material and the solid electrolyte must have sufficient adhesion. If this adhesion is reduced due to repeated expansion and contraction during charge and discharge, lithium electrodeposition occurs, resulting in a decrease in ionic conductivity.

[0004] Regarding this point, for example, Patent Document 1 below discloses a structure in which both surfaces of a dense solid electrolyte layer are sandwiched between porous solid electrolytes, and a composite material is filled in the porous pores to integrate the electrode composite material and the solid electrolyte.

[0005] [Prior technical literature]

[0006] (Patent Document)

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2008-226666 Summary of the Invention

[0008] [Problems to be solved by the invention]

[0009] However, even in Patent Document 1, the porous solid electrolyte is a so-called green sheet, and the adhesion between the electrode composite and the solid electrolyte is insufficient, requiring further improvement.

[0010] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to improve the adhesion between an electrode composite and a solid electrolyte, thereby suppressing the electrodeposition of lithium caused by a decrease in adhesion.

[0011] [Technical means to solve the problem]

[0012] The present inventors have discovered that the above-mentioned problems can be solved by laminating an electrode composite layer and a solid electrolyte layer in a planar manner within the pores of a porous metal body, thereby completing the present invention.

[0013] (1) An electrode comprising:

[0014] A planar electrode current collector made of a porous metal body;

[0015] an electrode composite material layer, wherein the pores of the aforementioned porous metal body are filled with an electrode composite material; and

[0016] A solid electrolyte layer, wherein the pores of the aforementioned porous metal body are filled with a solid electrolyte; and

[0017] The electrode composite layer and the solid electrolyte layer are laminated in a planar manner within the pores of the porous metal body.

[0018] According to the invention of (1), by laminating the electrode composite layer and the solid electrolyte layer in a planar shape inside the pores of the porous metal body, the volume change during the charge and discharge process can be followed, thereby suppressing the electrodeposition of lithium.

[0019] (2) The electrode according to (1), comprising a tab extending from one end of the porous metal body.

[0020] In a plan view, at least an end edge of the solid electrolyte layer in the tab direction is located beyond an end edge of the electrode composite layer in the tab direction.

[0021] According to the invention of (2), short circuits between the positive and negative electrodes and breakage of the tabs serving as current collectors can be effectively prevented.

[0022] (3) An electrode obtained by combining two electrodes of the same polarity as described in (1) or (2), and

[0023] The electrode composite material layers constituting each electrode are joined so as to face each other.

[0024] According to the invention of (3), the energy density can be improved by adopting a structure in which a pair of identical electrodes are bonded together.

[0025] (4) A secondary battery in which a positive electrode and a negative electrode are joined so that the respective solid electrolyte layers face each other,

[0026] The positive electrode is the positive electrode described in (1) or (2) including a positive electrode composite as the aforementioned electrode composite.

[0027] The negative electrode is the negative electrode described in (1) or (2) including a negative electrode composite as the aforementioned electrode composite.

[0028] The bonding is performed in such a manner that the respective solid electrolyte layers face each other.

[0029] According to the invention of (4), a secondary battery having the effects of (1) to (3) can be provided.

[0030] (5) The secondary battery according to (4), wherein a second solid electrolyte layer is disposed between the solid electrolyte layers.

[0031] According to the invention of (5), the effect of preventing short circuits between the positive and negative electrodes can be enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a perspective view showing one embodiment of a secondary battery using the electrode of the present invention.

[0033] Figure 2 This is a process diagram showing an example of a method for producing an electrode of the present invention.

[0034] Figure 3 This is a process diagram showing another example of the method for producing the electrode of the present invention. DETAILED DESCRIPTION

[0035] An embodiment of the present invention will be described below with reference to the accompanying drawings. The present invention is not limited to the following embodiment. Furthermore, while the following embodiment uses a solid-state lithium-ion battery as an example, the present invention can also be applied to batteries other than lithium-ion batteries.

[0036] [First embodiment]

[0037] <Overall structure of a lithium-ion secondary battery>

[0038] like Figure 1 As shown, the present embodiment Figure 1 The lithium-ion secondary battery 100 is a solid-state battery and is an electrode laminate in which positive electrodes 10, solid electrolyte layers 30, and negative electrodes 20 are alternately laminated. A positive electrode tab 11 and a negative electrode tab 21 extend from one end of the current collector of each electrode of the electrode laminate. Figure 1 This figure shows a state before the tabs are bundled, and the bundling portion is omitted.

[0039] Next, the respective components will be described.

[0040] <Positive and negative electrodes>

[0041] In this embodiment, the current collectors of the positive electrode 10 and the negative electrode 20 are each composed of a porous metal body having mutually continuous pores (connected pores).

[0042] The holes in each current collector are filled with an electrode material (positive electrode material, negative electrode material) containing an electrode active material. In contrast, the positive electrode tab 11 and the negative electrode tab 21 are unfilled areas where no electrode material is placed.

[0043] (Current Collector)

[0044] The current collector is composed of a porous metal body having mutually continuous pores. The mutually continuous pores allow the interior of the pores to be filled with a positive electrode composite material or a negative electrode composite material containing an electrode active material, thereby increasing the amount of electrode active material per unit area of ​​the electrode layer. The porous metal body is not particularly limited as long as it has mutually continuous pores. Examples thereof include foamed metal, metal mesh, porous metal, punched metal, and metal nonwoven fabrics having pores formed by foaming.

[0045] The metal used for the porous metal body is not particularly limited as long as it has conductivity, and examples thereof include nickel, aluminum, stainless steel, titanium, copper, silver, etc. Among them, foamed aluminum, foamed nickel, and foamed stainless steel are preferred as the current collector constituting the positive electrode, and foamed copper and foamed stainless steel are preferred as the current collector constituting the negative electrode.

[0046] By using a current collector of a porous metal body, the amount of active material per unit area of ​​the electrode can be increased. As a result, the volume energy density of the lithium-ion secondary battery can be improved. In addition, since the positive electrode composite material and the negative electrode composite material are easy to fix, unlike the electrodes that use metal foil as the current collector in the past, when increasing the film thickness of the electrode composite material layer, there is no need to thicken the coating slurry forming the electrode composite material layer. Therefore, the adhesive such as the organic polymer compound required for thickening can be reduced. Therefore, the capacity per unit area of ​​the electrode can be increased, thereby realizing the high capacity of the lithium-ion secondary battery.

[0047] (Electrode composite material)

[0048] The positive electrode composite material and the negative electrode composite material are respectively arranged in the pores formed inside the current collector. The positive electrode composite material and the negative electrode composite material contain positive electrode active material and negative electrode active material as essential components, respectively.

[0049] (Electrode active material)

[0050] The positive electrode active material is not particularly limited as long as it can absorb and release lithium ions, and examples thereof include LiCoO2, Li(Ni 5 / 10 Co 2 / 10 Mn 3 / 10 )O2、Li(Ni 6 / 10 Co 2 / 10 Mn 2 / 10 )O2、Li(Ni 8 / 10 Co 1 / 10 Mn 1 / 10 )O2、Li(Ni 0.8 Co 0.15 Al 0.05 )O2、Li(Ni 1 / 6 Co 4 / 6 Mn 1 / 6)O2、Li(Ni 1 / 3 Co 1 / 3 Mn 1 / 3 )O2, LiCoO4, LiMn2O4, LiNiO2, LiFePO4, lithium sulfide, sulfur, etc.

[0051] The negative electrode active material is not particularly limited as long as it can absorb and release lithium ions. Examples thereof include metallic lithium, lithium alloys, metal oxides, metal sulfides, metal nitrides, Si, SiO, and carbon materials such as artificial graphite, natural graphite, hard carbon, and soft carbon.

[0052] (Other ingredients)

[0053] The electrode composite material may also contain other components in addition to the electrode active material and the ion conductive particles. There is no particular limitation on the other components, as long as they are components that can be used when making lithium ion secondary batteries. Examples include conductive additives and binders. Examples of conductive additives for the positive electrode include acetylene black, and examples of binders for the positive electrode include polyvinylidene fluoride. Examples of binders for the negative electrode include sodium carboxymethyl cellulose, styrene-butadiene rubber, and sodium polyacrylate.

[0054] (Methods for manufacturing positive and negative electrodes)

[0055] The positive electrode 10 and the negative electrode 20 are obtained by filling the pores of a porous metal body having continuous pores, which serves as a current collector, with an electrode composite. First, the electrode active material and, if necessary, a binder or auxiliary agent are uniformly mixed using conventional methods to obtain an electrode composite composition adjusted to a specific viscosity, preferably in a paste form.

[0056] Next, the electrode composite composition is applied as an electrode composite to the pores of a porous metal body serving as a current collector. The method for applying the electrode composite to the current collector is not particularly limited, and examples thereof include using a plunger-type die coater to apply pressure to fill a slurry containing the electrode composite into the pores of the current collector. Alternatively, the porous metal body may be impregnated with the ion conductor layer by impregnation.

[0057] Furthermore, the solid electrolyte layer 17 filling the pores of the porous metal body 15 described below can also be formed using the same method.

[0058] Solid electrolyte layer

[0059] like Figure 1 As shown, in the present invention, a second solid electrolyte layer 30 may be formed between the positive electrode 10 and the negative electrode 20. The same material may also be used for the solid electrolyte layer 17 filling the pores of the porous metal body 15 described below.

[0060] The solid electrolyte constituting the second solid electrolyte layer 30 is not particularly limited, and examples thereof include sulfide-based solid electrolyte materials, oxide-based solid electrolyte materials, nitride-based solid electrolyte materials, and halide-based solid electrolyte materials. As sulfide-based solid electrolyte materials, for example, if it is a lithium-ion battery, LPS-based halogens (Cl, Br, I), or Li2S-P2S5, Li2S-P2S5-LiI, etc. can be listed. In addition, the above-mentioned description of "Li2S-P2S5" refers to a sulfide-based solid electrolyte material formed using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions. As oxide-based solid electrolyte materials, for example, if it is a lithium-ion battery, NASICON-type oxides, garnet-type oxides, and perovskite-type oxides can be listed. As NASICON-type oxides, for example, oxides containing Li, Al, Ti, P, and O (such as Li 1.5 Al 0.5 Ti 1.5 (PO4)3). Examples of garnet-type oxides include oxides containing Li, La, Zr, and O (e.g., Li7La3Zr2O 12 ). Examples of perovskite-type oxides include oxides containing Li, La, Ti, and O (eg, LiLaTiO 3 ).

[0061] <Electrode Structure>

[0062] [First embodiment]

[0063] Next, use Figure 2 One embodiment of the electrode that is a feature of the present invention will be described in detail. Figure 2 1 is a process diagram showing an example of a method for manufacturing an electrode of the present invention. Hereinafter, the positive electrode 10 is used as an example, but the same is also applicable to the negative electrode 20.

[0064] Figure 2 (a) Yes Figure 1 The XZ cross-sectional view of the positive electrode 10a in FIG. The positive electrode 10a includes: a planar electrode current collector composed of a metal porous body 15; an electrode composite layer (positive electrode composite layer) 16, in which the pores of the metal porous body 15 are filled with an electrode composite; and a solid electrolyte layer 17, in which the pores of the metal porous body 15 are filled with a solid electrolyte. The electrode composite layer 16 and the solid electrolyte layer 17 are laminated into a planar shape in the pores of the metal porous body 15. Figure 1 in Figure 2 An electrode composite layer 16 is formed on the top of Figure 2 A solid electrolyte layer 17 is formed below.

[0065] The "planar shape" in the present invention means that the metal porous body 15 has Figure 1 The term "laminated in a planar shape" means that the electrode composite layer 16 and the solid electrolyte layer 17 are laminated vertically (along the Z direction) in the pores of the porous metal body 15 .

[0066] The positive electrode 10a described above can be obtained by, for example, applying the electrode composite layer 16 and the solid electrolyte layer 17 to the front and back sides of the porous metal body 15, respectively, with a specific viscosity, and applying the layers separately from the top and bottom. By filling the pores of the porous metal body 15 with each layer, an electrode can be obtained in which the porous metal body 15 uses elastic force to follow the volume changes during charge and discharge, thereby suppressing lithium electrodeposition. Furthermore, by using the porous metal body 15 as a matrix, the adhesion between the electrode composite layer 16 and the solid electrolyte layer 17 can be maintained.

[0067] At this time, if Figure 2 As shown in (a), when viewed in cross section, the end edge 17a of the solid electrolyte layer 17 in the direction of the pole tab is located at a position further extended than the end edge 16a of the electrode composite layer 16 in the direction of the pole tab. In other words, when viewed from above, at least the end edge 17a of the solid electrolyte layer in the direction of the pole tab is located at a position that exceeds the end edge 16a of the electrode composite layer in the direction of the pole tab. This can effectively prevent the short circuit of the positive and negative electrodes and the breakage of the pole tab as a current collector. In addition, as Figure 2 As shown in (a), the edge 17a only needs to be positioned beyond the edge 16a. For example, the edge 17a may be configured to cover the edge 16a.

[0068] Here, in the present invention, it is also possible to directly use Figure 2 (a) The positive electrode 10a is used as the positive electrode, but in this embodiment, as Figure 2 As shown in Figure (b), identical electrodes 10a and 10b are bonded together using a press or the like, with the electrode composite layers 16 facing each other, to form a positive electrode 10c. This preferred structure of bonding a pair of identical electrodes together can improve energy density. Furthermore, since the porous metal bodies 15 are intertwined and bonded at the bonding surface, the bonding surface can be firmly maintained.

[0069] Finally, if Figure 2 As shown in (c), the second solid electrolyte layer 30, the positive electrode 10c, the second solid electrolyte layer 30, the negative electrode 20c and the solid electrolyte layer 30 are laminated. In this way, by laminating the positive electrode and the negative electrode through the independent second solid electrolyte layer 30, a Figure 1The lithium ion secondary battery 100 is similar to the positive electrode 10c. The negative electrode 20c has an electrode composite layer (negative electrode composite) 26 and a solid electrolyte layer 27 (same as the solid electrolyte layer 17) laminated on top of each other in the pores of the porous metal body 25.

[0070] In the present invention, the second solid electrolyte layer 30 is not an essential component, but is preferably provided from the viewpoint of preventing a short circuit between the positive and negative electrodes.

[0071] [Second embodiment]

[0072] Figure 3 FIG is a diagram showing another embodiment of the present invention. In this embodiment, Figure 3 (a) is the same as the first embodiment in that the positive electrode 10a is obtained, but Figure 3 In (b), the solid electrolyte layer 30a is formed on the solid electrolyte layer 17 by coating to produce the positive electrode / solid electrolyte laminate electrode 10d. Figure 3 As shown in (c), the same electrodes 10d and 10d are joined together by a press machine or the like so that the electrode composite layers 16 face each other to form the positive electrode 10e. The negative electrode 20e is also manufactured in the same manner, and finally, the positive electrode 10e and the negative electrode 20e are laminated. This method can also be used to obtain Figure 1 A lithium-ion secondary battery 100 is provided.

[0073] In this case, only Figure 3 Any one of the opposing solid electrolyte layers 30a in (c).

[0074] While preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments and can be modified as appropriate.

[0075] Reference numerals

[0076] 10 positive electrode

[0077] 10a positive electrode

[0078] 10b positive electrode

[0079] 10c positive electrode

[0080] 10e positive electrode

[0081] 11. Positive electrode tab

[0082] 15 Metal porous bodies

[0083] 16 Electrode composite layer (positive electrode composite layer)

[0084] 16a End edge

[0085] 17 Solid electrolyte layer

[0086] 17a End edge

[0087] 20 negative electrode

[0088] 20c negative electrode

[0089] 20e negative electrode

[0090] 21. Negative electrode tab

[0091] 26 Electrode composite layer (negative electrode composite layer)

[0092] 26a End edge

[0093] 27 Solid electrolyte layer

[0094] 27a End edge

[0095] 30 Second solid electrolyte layer

[0096] 100 lithium-ion secondary batteries

Claims

1. An electrode comprising: A planar electrode current collector composed of a porous metal body; An electrode composite material layer, wherein the pores of the aforementioned porous metal body are filled with an electrode composite material; a solid electrolyte layer, wherein the pores of the porous metal body are different from the pores filled with the electrode composite material layer; and A tab extending from one end of the porous metal body, The electrode composite layer is formed along one of the two end surfaces in the thickness direction of the porous metal body, and the solid electrolyte layer is formed along the other of the two end surfaces in the thickness direction of the porous metal body. The electrode composite layer and the solid electrolyte layer are laminated in a planar shape within the pores of the porous metal body, and when viewed from above, at least the end edge of the solid electrolyte layer in the direction of the electrode tab is located beyond the end edge of the electrode composite layer in the direction of the electrode tab.

2. An electrode assembly, which is obtained by combining two electrodes of the same polarity as claimed in claim 1, and The electrode composite material layers constituting each electrode are joined so as to face each other.

3. A secondary battery comprising the electrode according to claim 1 comprising a positive electrode composite as the electrode composite and constituting a positive electrode and the electrode according to claim 1 comprising a negative electrode composite as the electrode composite and constituting a negative electrode, with the respective solid electrolyte layers facing each other.

4. The secondary battery according to claim 3, wherein A second solid electrolyte layer is arranged between the solid electrolyte layers.

5. A secondary battery comprising an electrode assembly according to claim 2 comprising a positive electrode composite as the aforementioned electrode composite and constituting a positive electrode and an electrode assembly according to claim 2 comprising a negative electrode composite as the aforementioned electrode composite and constituting a negative electrode, joined in such a manner that the respective solid electrolyte layers face each other.

6. The secondary battery according to claim 5, wherein A second solid electrolyte layer is arranged between the solid electrolyte layers.

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