Current collector structure and secondary battery using the same

Abstract

The problem to be solved by the present invention is to prevent the fracture of the joint when the collector tabs are bundled and joined, and also to prevent the rotation of the external connection tab. In order to solve the above problems, the present invention provides a collector structure, comprising: a plurality of electrode collectors, which are composed of a metal porous body; and a collector tab, which extends from one end of the metal porous body in each of the aforementioned electrode collectors; and a joint portion for joining with the external connection tab is formed at the tab bundling position where the plurality of collector tabs are bundled, the plurality of collector tabs are arranged to sandwich the aforementioned external connection tab from above and below the external connection tab, the width of the plurality of collector tabs is greater than the width of the external connection tab, and the width of the joint portion is at least greater than the width of the external connection tab.

Description

Technical Field

[0001] The present invention relates to a current collector structure and a secondary battery using the same. Background Art

[0002] In the past, lithium-ion secondary batteries have been widely used as secondary batteries with high energy density. Liquid lithium-ion secondary batteries have the following battery structure: there is a separator between the positive electrode and the negative electrode, and it is filled with a liquid electrolyte (electrolyte). And, when the electrolyte is a solid-state battery, it has a battery structure in which a solid electrolyte is present between the positive electrode and the negative electrode. Multiple single cells are laminated to form a lithium-ion secondary battery.

[0003] It is proposed to use a metal porous body as a current collector constituting a positive electrode and a negative electrode (for example, refer to Patent Document 1). The metal porous body has a mesh structure with fine pores and a large surface area. By filling an electrode composite material containing an electrode active material into the interior of the mesh structure, the amount of electrode active material per unit area of ​​the electrode layer can be increased.

[0004] [Prior technical literature]

[0005] (Patent Document)

[0006] Patent Document 1: Japanese Patent Application Publication No. 2012-186139 Summary of the invention

[0007] [Problems to be solved by the invention]

[0008] When a metal porous body is used as a current collector, the positive electrode tab and the negative electrode tab are bundled separately and then connected to an external connection tab at the tab bundling position by ultrasonic wave or welding to form a joint.

[0009] The porous metal body constituting the pole ear usually has pores of more than 90% by volume. Therefore, if compression bonding is performed, the thickness at the joint will be reduced to about 1 / 10. At this time, there is the following problem: a large height difference (thickness difference) is generated between the joint and its surroundings, and the pole ear on the upper side of the joint will become a shape that is pressed and cut by a pressure member such as an ultrasonic horn, especially the positive pole ear on the upper part of the laminate is easy to break.

[0010] Furthermore, at the joint, the external connection tab is easily rotated with the joint as a base point, which may also cause the tab to break.

[0011] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to prevent the joint portion from being broken when the current collector tabs are bundled and joined.

[0012] [Technical means to solve the problem]

[0013] The inventors of the present invention have found that the above-mentioned problem can be solved by arranging a plurality of tabs so as to sandwich the external connection tabs from above and below the external connection tabs, and arranging the tabs so that the width of the tabs is larger than the width of the external connection tabs so as to cover the external connection tabs, thereby completing the present invention. That is, the present invention provides the following solution.

[0014] (1) A current collector structure comprising:

[0015] A plurality of electrode current collectors, composed of a metal porous body; and

[0016] A collector tab extends from one end of the aforementioned porous metal body in each aforementioned electrode collector; and

[0017] A joint portion for joining with an external connection tab is formed at a tab clustering position where the plurality of current collector tabs are clustered.

[0018] The plurality of current collector tabs are arranged to sandwich the external connection tabs from above and below the external connection tabs.

[0019] The width of the plurality of current collector tabs is greater than the width of the external connection tabs.

[0020] The width of the joint portion is at least equal to or greater than the width of the external connection tab.

[0021] According to the invention of (1), by configuring the plurality of current collector tabs to be separated up and down, the external connection tabs are sandwiched from above and below the external connection tabs, and the width of the current collector tabs is further made larger than the width of the external connection tabs, so that the external connection tabs can be wrapped and covered by the current collector tabs. Thus, the external connection tabs can be prevented from moving or rotating, thereby preventing the current collector tabs from breaking.

[0022] (2) The current collector structure according to (1), wherein the joint portion is formed across the width of the external connection tab.

[0023] Compression-joined portions for compressively joining the upper and lower current collector tabs are provided on both sides exceeding the width of the external connection tab.

[0024] According to the invention of (2), the upper and lower porous metal bodies are compression-bonded in an intertwined state outside the both side edges of the external connection tab, thereby further suppressing the external connection tab from moving or rotating.

[0025] (3) The current collector structure according to (2), wherein in the compression joint, protrusions extending in the width direction from both side edges of the external connection tab are respectively arranged between the upper and lower current collector tabs.

[0026] According to the invention of (3), by providing the protrusion extending from the external connection tab, the rotation of the external connection tab can be effectively suppressed.

[0027] (4) A secondary battery having the current collector structure described in any one of (1) to (3), and comprising:

[0028] The positive electrode and / or the negative electrode comprises a composite material filled region filled with the electrode composite material inside the metal porous body of the electrode current collector and a composite material unfilled region not filled with the electrode composite material; and,

[0029] an electrolyte disposed between the two electrodes; and

[0030] The region of the electrode current collector that is not filled with the composite material constitutes the current collector tab.

[0031] According to the invention of (4), a secondary battery that achieves the effects of (1) to (3) can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 1 is a schematic cross-sectional view showing an embodiment of the current collector structure of the present invention.

[0033] Figure 2 yes Figure 1 An enlarged top view of the tab clustering position P.

[0034] Figure 3 yes Figure 2 XX section diagram in .

[0035] Figure 4 It is shown Figure 3 A cross-sectional view of a modified example of .

[0036] Figure 5 It is shown Figure 2 A top view of a modified example of .

[0037] Figure 6 yes Figure 5 YY section diagram in . DETAILED DESCRIPTION

[0038] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The content of the present invention is not limited to the description of the following embodiment. In addition, in the following embodiment, a lithium-ion battery of a solid-state battery is used as an example for description, but the present invention is not limited to a solid-state battery, and can also be applied to a secondary battery having a liquid electrolyte and a separator. Furthermore, it can also be applied to batteries other than lithium-ion batteries.

[0039] <Overall structure of the current collector>

[0040] like Figure 1 As shown, in the current collector structure 100 of the present embodiment, a plurality of positive electrode tabs 11 extend from one end of the current collector constituting the positive electrode 10, are then bundled at the tab bundling position, and are electrically connected to the external connection tab 50 at the joint 60. In particular, the details of the joint 60 will be described below. In addition, the negative electrode not shown in the figure is also of the same structure as the positive electrode. In a solid-state battery having a current collector structure 100, the solid-state battery is composed of an electrode laminate and a current collector structure 100, and the electrode laminate is formed by alternately laminating the positive electrode 10, the solid electrolyte layer (not shown) and the negative electrode (not shown).

[0041] Hereinafter, members constituting the electrode laminate will be described.

[0042] <Positive and negative electrodes>

[0043] In this embodiment, the current collectors of the positive electrode and the negative electrode are each composed of a porous metal body having pores (interconnected pores) that are continuous with each other.

[0044] The holes of each current collector are composite material filled regions filled with electrode composite materials (positive composite material, negative composite material) containing electrode active materials, respectively. On the contrary, the positive electrode tab 11 and the negative electrode tab are composite material unfilled regions where electrode composite materials are not filled.

[0045] (Current Collector)

[0046] The current collector is composed of a metal porous body having mutually continuous pores. By having mutually continuous pores, the positive electrode composite material and the negative electrode composite material containing the electrode active material can be filled inside the pores, thereby increasing the amount of the electrode active material per unit area of ​​the electrode layer. As the above-mentioned metal porous body, as long as it has mutually continuous pores, there is no particular limitation, and examples thereof include foamed metal, metal mesh, porous metal, punching metal, metal nonwoven fabric, etc. having pores formed by foaming.

[0047] 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.

[0048] By using a current collector of a metal porous body, the amount of active material per unit area of ​​the electrode can be increased, and 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 can become easy to fix, it is different from the previous electrode using metal foil as the current collector. When the thick film of the electrode composite material layer is increased, it is not necessary to thicken the coating slurry forming the electrode composite material layer. Therefore, it is possible to reduce the adhesive such as the organic polymer compound required for thickening. Therefore, it is possible to increase the capacity per unit area of ​​the electrode, so that the high capacity of the lithium ion secondary battery can be achieved.

[0049] (Electrode Composite Materials)

[0050] 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 a positive electrode active material and a negative electrode active material as essential components, respectively.

[0051] (Electrode Active Material)

[0052] 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.

[0053] The negative electrode active material is not particularly limited as long as it can absorb and release lithium ions, and 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.

[0054] (Other ingredients)

[0055] The electrode composite material may also arbitrarily contain other components other than the electrode active material and the ion conductive particles. As other components, there is no particular limitation, as long as they are components that can be used when making lithium ion secondary batteries. For example, conductive aids, adhesives, etc. can be listed. As conductive aids for the positive electrode, acetylene black, etc. can be exemplified, and as adhesives for the positive electrode, polyvinylidene fluoride, etc. can be exemplified. As adhesives for the negative electrode, sodium carboxymethyl cellulose, styrene-butadiene rubber, sodium polyacrylate, etc. can be exemplified.

[0056] (Method for manufacturing positive electrode and negative electrode)

[0057] The positive electrode 10 and the negative electrode 20 are obtained by filling the pores of a metal porous body having mutually continuous pores as a current collector with an electrode composite material. First, the electrode active material and, if necessary, a binder or an auxiliary agent are uniformly mixed using a conventionally known method to obtain an electrode composite material composition adjusted to a specific viscosity and preferably in a paste state.

[0058] Next, the electrode composite material composition is filled as an electrode composite material into the pores of the metal porous body as a current collector. The method of filling the electrode composite material into the current collector is not particularly limited, and the following methods can be cited: for example, a plunger-type die coater is used to apply pressure to fill the slurry containing the electrode composite material into the pores of the current collector. In addition to the above, the ion conductor layer can also be impregnated into the interior of the metal porous body by impregnation.

[0059] <Solid electrolyte layer>

[0060] The solid electrolyte constituting the solid electrolyte layer 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 "Li2S-P2S5" record refers to a sulfide-based solid electrolyte material formed using a raw material composition containing Li2S and P2S5, and the other records are the same. As oxide-based solid electrolyte materials, for example, if it is a lithium-ion battery, NASICON (Na superionic conductor) type oxides, garnet-type oxides, perovskite-type oxides, etc. 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] <Liquid Electrolyte>

[0062] The electrolyte dissolved in the non-aqueous solvent is not particularly limited, and examples thereof include LiPF6, LiBF4, LiClO4, LiN(SO2CF3), LiN(SO2C2F5)2, LiCF3SO3, LiC4F9SO3, LiC(SO2CF3)3, LiF, LiCl, LiI, Li2S, Li3N, Li3P, Li 10 GeP2S 12 (LGPS), Li3PS4, Li6PS5Cl, Li7P2S8I, Li x PO y N z (x=2y+3z-5, LiPON), Li7La3Zr2O 12 (LLZO), Li 3x La 2 / 3-x TiO3(LLTO), Li 1+x Al x Ti 2-x (PO4)3(0≦x≦1, LATP), Li 1.5 Al 0.5 Ge 1.5 (PO4)3(LAGP), Li 1+x+y Al x Ti 2-x Si y P 3-y O 12 , Li 1+x+y Al x (Ti,Ge) 2-x Si y P 3-y O 12 , Li 4- 2x Zn x GeO4 (LISICON), etc. These may be used alone or in combination of two or more.

[0063] The nonaqueous solvent contained in the electrolyte solution is not particularly limited, and examples thereof include aprotic solvents such as carbonates, esters, ethers, nitriles, sulfones, and lactones. Specifically, there can be mentioned ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE), tetrahydrofuran (THF), 2-methyltetrahydrofuran, dioxane, 1,3-dioxolane, diethylene glycol dimethyl ether, ethylene glycol dimethyl ether, acetonitrile (AN), propionitrile, nitromethane, N,N-dimethylformamide (DMF), dimethyl sulfoxide, sulfolane, γ-butyrolactone, etc. The above-mentioned can be used alone or in combination of two or more.

[0064] (Diaphragm)

[0065] In particular, when a liquid electrolyte is used, the lithium ion secondary battery of this embodiment may also include a separator. The separator is located between the positive electrode and the negative electrode. Its material and thickness are not particularly limited, and well-known separators that can be used in lithium ion secondary batteries such as polyethylene or polypropylene can be used.

[0066] <Current Collector Structure>

[0067] Next, use Figures 1 to 3 The current collector structure which is a feature of the present invention will be described in detail. Figure 1 is a schematic cross-sectional view showing an embodiment of the current collector structure of the present invention, Figure 2 yes Figure 1 An enlarged top view of the tab cluster position P, Figure 3 yes Figure 2 XX section diagram in .

[0068] like Figure 1 As shown, in the current collector structure 100 of the present embodiment, a plurality of positive electrode tabs 11 extend from one end of the current collector constituting the positive electrode 10, are bundled at the tab bundling position, and are electrically connected to the external connection tab 50 at the junction 60. The current collector structure on the positive electrode side is described below as an example, and the negative electrode side has the same structure, so its description is omitted.

[0069] The positive electrode 10 is formed of a metal porous body as a whole, and there are composite material filled areas filled with electrode composite materials and composite material unfilled areas not filled with electrode composite materials, and the composite material unfilled areas constitute positive electrode tabs 11. The positive electrode tabs 11 are respectively bundled at the tab bundling position P, and in this embodiment, they are sandwiched between the external connection tabs 50 and distributed up and down, with the upper three positive electrode tabs 11a arranged above the external connection tabs 50, and the lower three positive electrode tabs 11b arranged below the external connection tabs 50. A pair of liner plates 70 are arranged in a manner of sandwiching the positive electrode tabs 11a and the positive electrode tabs 11b, and ultrasonic bonding is performed from the top and bottom via the liner plates 70. In this way, a plurality of electrode tabs are arranged above and below (front and back) the external connection tabs, thereby preventing the electrode tabs from breaking.

[0070] like Figure 2 , Figure 3 As shown, in the xy plan view, the external connection tab 50 is a plate-like member having a width direction (width W1) and a length direction, and the cross section is a rectangular shape. At the tab clustering position P, the positive electrode tab 11 has a width W4, which is greater than the width W1 of the external connection tab 50. Therefore, Figure 3 As shown, they are arranged so as to sandwich the external connection tab 50 ( W4 > W1 ).

[0071] The width of the liner 70 is W2, which is greater than the width W1 of the external connection tab 50 (W2>W1). Figure 3 As shown, the joint 60 is formed across the entire width W1 on the front and back sides of the external connection tab 50. That is, the width W3 of the joint 60 is substantially equal to the width W1 (W3=W1). Thus, the positive electrode tab 11 and the external connection tab 50 can be reliably joined.

[0072] exist Figure 3 In the embodiment, on both sides exceeding the width of the external connection tab 50, there is a compression joint 80 that continuously compresses and joins the above-mentioned collector tabs arranged above and below from the joint 60. The compression joint 80 is formed by compressing and joining the upper and lower metal porous bodies to each other in an intertwined state. Thereby, the movement or rotation of the external connection tab can be further prevented. In this embodiment, the compression joint 80 is formed across the entire width direction of the positive electrode tab 11, but it is not limited to this. The compression joint can also be formed to a part of the width direction of the positive electrode tab 11 that is continuous with the joint 60. The compression joint 80 can be formed by a pressing step different from the joint 60.

[0073] Figure 4 It is shown Figure 3 Figure 1 shows a modified example of . Figure 3 The difference is that the shape of the lining plate 70a is different. Figure 4 (a) is a diagram showing a state before the bonding portion is formed, Figure 4 (b) is a diagram showing a state after the joint is formed. In this embodiment, the upper and lower liner plates 70a are deformed along the cross-sectional shape of the external connection tab 50 during the pressing step, and extend along the width direction of the positive electrode tab 11 via the inclined portion to form the joint. As a result, the movement or rotation of the external connection tab can be further suppressed.

[0074] Figure 5 It is shown Figure 2 A top view of a modified example of Figure 6 yes Figure 5 In this modification, protrusions 50a, 50a are formed respectively from both side edges of the external connection tab 50 in the width direction. By forming the protrusions 50a, it is possible to more effectively prevent the external connection tab 50 from Figure 5 In the direction indicated by the arrow, that is, Figure 5 Rotation in the xy plane.

[0075] As mentioned above, although the preferred embodiment of the present invention was described, the content of the present invention is not limited to the above-mentioned embodiment, and it can be modified appropriately.

[0076] Reference numerals

[0077] 10 Positive electrode

[0078] 11. Positive electrode tab

[0079] 11a, 11b positive electrode tab

[0080] 50 External connection tabs

[0081] 50a Protrusion

[0082] 60 Joint

[0083] 70, 70a lining

[0084] 80 Compression joint

[0085] 100 Collector Construction

[0086] P Tab cluster position

Claims

1. A current collector structure, comprising: A plurality of electrode current collectors, composed of a metal porous body; and A collector tab extends from one end of the aforementioned porous metal body in each aforementioned electrode collector; and The current collector tab is made of a porous metal body. A joint portion for joining with an external connection tab is formed at a tab clustering position where the plurality of current collector tabs are clustered. The plurality of current collector tabs are arranged to sandwich the external connection tabs from above and below the external connection tabs. The width of the plurality of current collector tabs is greater than the width of the external connection tabs. The joint portion is formed across the width of the external connection tab. Compression-joined portions for compressively joining the upper and lower current collector tabs are provided on both sides exceeding the width of the external connection tab.

2. The current collector structure according to claim 1, wherein: In the compression joint, protrusions extending in the width direction from both side edges of the external connection tab are respectively arranged between the upper and lower current collector tabs.

3. A secondary battery having the current collector structure according to claim 1 or 2, and comprising: The positive electrode and / or the negative electrode comprises a composite material filled region filled with the electrode composite material inside the metal porous body of the electrode current collector and a composite material unfilled region not filled with the electrode composite material; and, an electrolyte disposed between the two electrodes; and The region of the electrode current collector that is not filled with the composite material constitutes the current collector tab.

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