Secondary batteries

Abstract

To provide a secondary battery that can appropriately suppress charging and discharging during abnormal conditions. [Solution] A secondary battery 1 comprises an electrode stack 2 in which a plurality of positive electrode layers 10 and a plurality of negative electrode layers 20 are stacked via a solid electrolyte layer 30, and an outer casing 3 that houses the electrode stack 2, wherein a positive electrode tab lead 4 protruding from the outer casing 3 is joined to the positive electrode current collector 11 of the positive electrode layer 10, and a resin member 7 capable of interrupting overcurrent in response to rising temperature is joined between the positive electrode current collector 11 and the positive electrode tab lead 4.

Description

[Technical Field]

[0001] This invention relates to a secondary battery. [Background technology]

[0002] In recent years, research and development has been conducted on rechargeable batteries that contribute to energy efficiency, in order to ensure that more people have access to affordable, reliable, sustainable, and advanced energy.

[0003] For example, Patent Document 1 describes a laminate film type lithium-ion secondary battery comprising a flat electrode body to which positive electrode leads and negative electrode leads are attached, an electrolyte, and a film-like outer material that houses the electrode body and the electrolyte. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6973489 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Research and development related to secondary batteries is being conducted to ensure safety by appropriately suppressing the charging and discharging of secondary batteries in the event of abnormalities such as thermal runaway. Regarding the suppression of charging and discharging during such abnormal situations, there was room for consideration from a structural perspective of secondary batteries.

[0006] This invention provides a secondary battery that can appropriately suppress charging and discharging during abnormal conditions. [Means for solving the problem]

[0007] The present invention An electrode laminate in which multiple positive electrode layers and multiple negative electrode layers are stacked with an electrolyte layer in between, A secondary battery comprising an outer casing that houses the electrode stack, Tab leads protruding from the outer casing are attached to the current collector of the positive electrode layer and the current collector of the negative electrode layer. A resin member capable of interrupting overcurrent in response to rising temperature is bonded between the current collector of at least one of the positive electrode layer and the negative electrode layer and the tab lead. [Effects of the Invention]

[0008] According to the present invention, a resin member capable of interrupting overcurrent in response to temperature rise is bonded between the current collector and the tab lead. For example, if the secondary battery becomes hot, the overcurrent flowing during charging and discharging of the secondary battery can be interrupted. Therefore, the safety of the secondary battery can be improved. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic cross-sectional view showing the internal structure of a secondary battery 1 according to one embodiment of the present invention. [Figure 2] Figure 2 is an enlarged cross-sectional view of the vicinity of the positive electrode tab lead 4. [Figure 3] Figure 3 shows the vicinity of the positive electrode tab lead 4 as viewed from the +Z side (-Z side). [Modes for carrying out the invention]

[0010] A secondary battery according to one embodiment of the present invention will be described below based on the attached drawings. In the following description, the arrow directions shown in the figures will be described as the X-axis direction, Y-axis direction, and Z-axis direction, respectively.

[0011] Figure 1 is a schematic cross-sectional view showing the internal structure of the secondary battery 1. The secondary battery 1 is configured as a solid-state battery having a solid electrolyte, for example. The secondary battery 1 is not particularly limited, but examples include lithium-ion secondary batteries and lithium-metal secondary batteries.

[0012] The secondary battery 1 includes an electrode laminate 2 in which a plurality of positive electrode layers 10 and a plurality of negative electrode layers 20 are laminated via a solid electrolyte layer 30, an exterior body 3 that houses the electrode laminate 2, and a positive electrode tab lead 4 and a negative electrode tab lead 5 that protrude from the exterior body 3. The secondary battery 1 has a shape that is long in the X-axis direction, and in the Z-axis direction, a plurality of positive electrode layers 10, a plurality of negative electrode layers 20, and the solid electrolyte layer 30 are laminated.

[0013] The exterior body 3 is, for example, a laminate film and seals the entire electrode laminate 2. As the laminate film, a three-layer laminate film in which an inner resin layer, a metal layer, and an outer resin layer are laminated in this order can be used. As materials for the inner resin layer and the outer resin layer, thermoplastic resins such as polyethylene terephthalate (PET), polyamide (nylon), and polypropylene (PP) can be used. As a material for the metal layer, for example, aluminum can be used.

[0014] The positive electrode tab lead 4 and the negative electrode tab lead 5 are provided at both ends in the longitudinal direction (X-axis direction) of the secondary battery 1 and partially protrude from the inside to the outside of the exterior body 3. The positive electrode tab lead 4 and the negative electrode tab lead 5 are plate-like members having conductivity. In the example shown here, the positive electrode tab lead 4 is provided on the +X side and the negative electrode tab lead 5 is provided on the -X side. Note that either the positive electrode tab lead 4 or the negative electrode tab lead 5 may be provided on the +X side or on the -X side.

[0015] FIG. 2 is an enlarged cross-sectional view of the vicinity of the positive electrode tab lead 4. In FIG. 2, the illustration of the exterior body 3 is omitted. First, the configurations of the positive electrode layer 10, the negative electrode layer 20, and the solid electrolyte layer 30 included in the electrode laminate 2 will be described.

[0016] Each positive electrode layer 10 has a positive electrode current collector 11 and a positive electrode active material layer laminated on each other. The positive electrode current collector 11 extends from the electrode laminate 2 to the +X side and is joined to the positive electrode tab lead 4 and electrically connected. The positive electrode tab lead 4 is formed of the same material (described later) as the positive electrode current collector 11.

[0017] The positive electrode current collector 11 has a function of collecting current of the positive electrode active material layer. The positive electrode current collector 11 is preferably composed of at least one material with high conductivity. Examples of materials with high conductivity include, for example, aluminum, aluminum alloy, stainless steel, nickel, iron, and titanium. Examples of the shape of the positive electrode current collector 11 include, for example, foil shape, thin plate shape, mesh shape, non-woven fabric shape, foam shape, etc. Also, in order to enhance the adhesion with the positive electrode active material layer, the surface of the positive electrode current collector 11 may be roughened.

[0018] The positive electrode active material layer contains, for example, a positive electrode active material and a solid electrolyte. The positive electrode active material layer is formed by applying a positive electrode slurry generated by kneading a positive electrode active material and a solid electrolyte together with a dispersion medium onto the positive electrode current collector 11 and drying it. Here, the dispersion medium contains a conductive auxiliary agent, a binder, and a solvent.

[0019] The positive electrode active material can be the same as those used for the positive electrodes of general solid-state batteries. Examples of the positive electrode active material include lithium-cobalt composite oxide, lithium-nickel composite oxide, lithium-nickel-cobalt composite oxide, lithium-nickel-manganese composite oxide, lithium-nickel-cobalt-manganese composite oxide, lithium-nickel-cobalt-aluminum composite oxide, etc. Specifically, the positive electrode active material is LiCoO2 or LiNi p Mn q Co r O2 (p + q + r = 1), LiNi p Al q Co r O2 (p + q + r = 1), etc. Also, the positive electrode active material may be a material containing metal elements such as Cr, Fe, V, Mg, Ca, Na, Ti, Zr, Nb, Mo, W, Cu, Zn, Ga, In, Sn, La, and Ce.

[0020] The solid electrolyte contained in the positive electrode active material layer can be the same as those used for general solid-state batteries, and examples include the same as the solid electrolyte (described later) contained in the solid electrolyte layer 30.

[0021] The conductive additives contained in the dispersion medium can be the same as those used in general solid-state batteries, and examples include carbon black, carbon nanotubes, graphene, and graphite particles.

[0022] The binder contained in the dispersion medium can be the same as that used in general solid-state batteries, and examples include polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polyisobutene (PIB), styrene-butadiene rubber (SBR), polyethylene-vinyl acetate copolymer (PEVA), nitrile rubber (NBR), and hydrogenated nitrile rubber (HNBR).

[0023] The solvent contained in the dispersion medium can be the same as that used in general solid-state batteries, and examples include organic solvents such as N-methyl-2-pyrrolidone (NMP), toluene, butyl butyrate, or alcohol, or water.

[0024] Each negative electrode layer 20 has a negative electrode current collector 21 and a negative electrode active material layer that are stacked on top of each other. The negative electrode current collector 21 extends from the electrode stack 2 towards the -X side and is electrically connected to the negative electrode tab lead 5 by joining them. The negative electrode tab lead 5 is made of the same material as the negative electrode current collector 21 (described later).

[0025] The negative electrode current collector 21 has the function of collecting current from the negative electrode active material layer. Preferably, the negative electrode current collector 21 is composed of at least one material with high conductivity. Examples of materials with high conductivity include copper, nickel, and stainless steel. Examples of the shape of the negative electrode current collector 21 include foil, thin plate, mesh, nonwoven fabric, and foam. In addition, the surface of the negative electrode current collector 21 may be roughened to improve adhesion with the negative electrode active material layer.

[0026] The negative electrode active material layer comprises, for example, a negative electrode active material and a solid electrolyte. The negative electrode active material layer is formed by kneading the negative electrode active material and solid electrolyte with a dispersion medium to produce a negative electrode slurry, which is then applied to the negative electrode current collector 21 and dried. The dispersion medium comprises a conductive additive, a binder, and a solvent, and each of these materials can be the same as those used in general solid-state batteries.

[0027] The negative electrode active material can be the same as that used in the negative electrode material of a typical solid-state battery. Examples of negative electrode active materials include silicon-based active materials such as lithium metal, lithium alloy, Si, and Si alloy, and lithium titanate (Li4Ti5O 12 Examples include lithium transition metal oxides such as ), transition metal oxides such as TiO2, Nb2O3, and WO3, metal sulfides, metal nitrides, carbon materials such as graphite, soft carbon, and hard carbon, and metallic indium.

[0028] The solid electrolyte contained in the negative electrode active material layer can be the same as that used in general solid-state batteries, and is similar to the solid electrolyte (described later) contained in the solid electrolyte layer 30.

[0029] The solid electrolyte layer 30 is formed between the positive electrode layer 10 and the negative electrode layer 20. The material constituting the solid electrolyte layer 30 can be the same as that used for the solid electrolyte of a general solid-state battery, for example, a sulfide-based solid electrolyte material. A sulfide-based solid electrolyte material usually contains a metal element (M) that acts as a conductive ion and sulfur (S). Examples of M include Li, Na, K, Mg, and Ca, with Li being preferred. In particular, a sulfide-based solid electrolyte material preferably contains Li, A (A is at least one selected from the group consisting of P, Si, Ge, Al, and B), and S, with phosphorus (P) being more preferred for A. Furthermore, a sulfide-based solid electrolyte material may also contain halogens such as Cl, Br, and I. This is because the inclusion of halogens improves ionic conductivity. A sulfide-based solid electrolyte material may also contain O.

[0030] Examples of sulfide-based solid electrolyte materials having ionic conductivity include, for example, Li2S-P2S5, Li2S-P2S5-LiI, Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (where m and n are positive numbers. Z is either Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li x MO y (where x and y are positive numbers. M is either P, Si, Ge, B, Al, Ga, or In). Note that the description "Li2S-P2S5" means a sulfide-based solid electrolyte material formed using a raw material composition containing Li2S and P2S5, and the same applies to other descriptions.

[0031] Further, as other examples of the material constituting the solid electrolyte layer 30, for example, oxide solid electrolytes, halide solid electrolytes, inorganic solid electrolytes such as lithium-containing salts, and polymer-based solid electrolytes such as polyethylene oxide can be mentioned. The material constituting the solid electrolyte layer 30 may be used alone or in combination of two or more.

[0032] Note that the secondary battery 1 may further include an intermediate layer disposed between the negative electrode layer 20 and the solid electrolyte layer 30. The intermediate layer has, for example, a function of uniformly depositing lithium metal when the secondary battery 1 is a lithium metal secondary battery. The substance constituting the intermediate layer is not particularly limited, and examples include metals that can alloy with lithium and amorphous carbon.

[0033] Next, the connection between the plurality of positive electrode layers 10 and the positive electrode tab lead 4 will be described in detail while referring to FIGS. 2 and 3.

[0034] The positive electrode current collectors 11 of the multiple positive electrode layers 10 extend from the electrode stack 2 towards the +X side, are concentrated, and joined to the positive electrode tab lead 4. The positive electrode current collectors 11 are connected to the -X side end of the positive electrode tab lead 4.

[0035] In this embodiment, positive electrode current collectors 11 are connected to both sides of the positive electrode tab lead 4. The positive electrode current collector 11 positioned on the +Z side relative to the positive electrode tab lead 4 is joined to the +Z side surface of the positive electrode tab lead 4, and the positive electrode current collector 11 positioned on the -Z side relative to the positive electrode tab lead 4 is joined to the -Z side surface of the positive electrode tab lead 4.

[0036] In this embodiment, a resin member 7 capable of interrupting overcurrent in response to rising temperature is bonded between the positive electrode current collector 11 and the positive electrode tab lead 4. The resin member 7 is manufactured by mixing conductive particles such as carbon black and nickel with a polymer material. The resin member 7 is provided both between the +Z side surface of the positive electrode tab lead 4 and the positive electrode current collector 11 located on the +Z side, and between the -Z side surface of the negative electrode tab lead 5 and the positive electrode current collector 11 located on the -Z side.

[0037] As described above, since the resin member 7 is bonded between the positive electrode current collector 11 and the positive electrode tab lead 4, if an abnormality such as thermal runaway occurs and the secondary battery 1 becomes hot, the resin member 7 can interrupt the overcurrent that flows during the charging and discharging of the secondary battery 1. Therefore, the safety of the secondary battery 1 can be improved.

[0038] The resin component 7 is, for example, an element with a positive temperature coefficient (PTC (Positive Temperature Coefficient) element). When a PTC element exceeds a predetermined temperature (Curie temperature), its electrical resistance increases sharply. Under normal conditions, the PTC element can conduct electricity, but at high temperatures exceeding the predetermined temperature, its electrical resistance increases sharply, interrupting the overcurrent. In this way, by using a PTC element for the resin component 7, a high current interruption effect can be ensured.

[0039] The positive electrode current collector 11, the resin member 7, and the positive electrode tab lead 4 are joined by ultrasonic bonding. Since ultrasonic bonding can join the positive electrode current collector 11, the resin member 7, and the positive electrode tab lead 4 in a solid state, it can reduce the electrical influence at room temperature at the joint compared to welding, etc. Furthermore, it can ensure sufficient adhesion at the joint.

[0040] Each positive electrode current collector 11 has an excess length between the electrode stack 2 and the positive electrode tab lead 4, allowing it to slacken. Specifically, the positive electrode current collector 11 positioned on the +Z side is positioned to slacken towards the +Z side, and the positive electrode current collector 11 positioned on the -Z side is positioned to slacken towards the -Z side. In this way, each positive electrode current collector 11 has an excess length, so even if the electrode stack 2 expands and contracts, it is possible to suppress the positive electrode tab lead 4 from being pulled by the positive electrode current collector 11 and causing displacement.

[0041] As described above, the positive electrode current collector 11 is joined to both sides of the positive electrode tab lead 4 via the resin member 7. With this configuration, the number of positive electrode current collectors 11 at a single joining point can be reduced compared to the case where the positive electrode current collector 11 is joined to only one side of the positive electrode tab lead 4. Therefore, good joining between the positive electrode current collector 11 and the positive electrode tab lead 4 via the resin member 7 can be achieved.

[0042] The resin member 7 has an extension portion 7a that extends from the joint with the positive electrode tab lead 4 toward the electrode stack 2 (specifically toward the -X side). The extension portion 7a restricts the positive electrode current collector 11 positioned on the +Z side from slackening toward the -Z side, and also restricts the positive electrode current collector 11 positioned on the -Z side from slackening toward the +Z side. The length of the extension portion 7a is preferably, for example, half or more of the distance between the positive electrode tab lead 4 and the electrode stack 2.

[0043] Thus, since the resin member 7 has an extended portion 7a, when, for example, the electrode laminate 2 is sealed with the outer casing 3, it is possible to prevent the positive electrode current collector 11 with excess length from being biased to one side in the Z-axis direction relative to the positive electrode tab lead 4. Specifically, it is possible to prevent both the positive electrode current collector 11 positioned on the +Z side and the positive electrode current collector 11 positioned on the -Z side from being biased to the -Z side (+Z side) and becoming loose. Therefore, the positive electrode current collector 11 can be positioned in a balanced manner relative to the positive electrode tab lead 4.

[0044] The extension portion 7a of the resin member 7 has a shape in which the thickness decreases from the joint to the tip on the -X side. This prevents the positive electrode current collector 11 from being biased to one side in the Z-axis direction relative to the positive electrode tab lead 4, while also reducing the weight of the resin member 7.

[0045] Figure 3 shows the vicinity of the positive electrode tab lead 4 as viewed from the +Z side (-Z side). The extension portion 7a of the resin member 7 is provided in the central part of the positive electrode current collector 11 in the Y-axis direction (width direction), and is not provided at the +Y side end or the -Y side end of the positive electrode current collector 11. This configuration prevents the positive electrode current collector 11 from being biased to one side in the Z-axis direction relative to the positive electrode tab lead 4, while also reducing the weight of the resin member 7. Furthermore, since the contact area between the resin member 7 and the positive electrode current collector 11 can be reduced, the effects of unnecessary contact can be reduced.

[0046] Furthermore, the width of the extension portion 7a of the resin member 7 decreases in the Y-axis direction as it extends in the extension direction (towards the -X side). Therefore, the weight of the resin member 7 can be reduced while preventing the positive electrode current collector 11 from being biased to one side in the Z-axis direction relative to the positive electrode tab lead 4.

[0047] Although one embodiment of the present invention has been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to this embodiment. It is clear to those skilled in the art that various modifications or alterations can be conceived within the scope of the claims, and these are also understood to naturally fall within the technical scope of the present invention. Furthermore, the components of the above embodiment may be combined in any way without departing from the spirit of the invention.

[0048] For example, the embodiment described above shows an example in which the positive electrode current collector 11 is joined to both sides of the positive electrode tab lead 4, but it is not limited to this. For example, the positive electrode current collector 11 may be joined to only one side of the positive electrode tab lead 4. Even with such a configuration, the resin member 7 provided between the positive electrode tab lead 4 and the positive electrode current collector 11 can interrupt the current flowing during charging and discharging of the secondary battery 1 when an abnormality such as thermal runaway occurs and the secondary battery 1 becomes hot. Therefore, the safety of the secondary battery 1 can be improved.

[0049] Furthermore, although the above-described embodiment shows an example in which a resin member 7 is provided between the positive electrode tab lead 4 and the positive electrode current collector 11, the invention is not limited to this. For example, a resin member 7 may be provided between the negative electrode tab lead 5 and the negative electrode current collector 21. Specifically, a resin member 7 may be provided only between the negative electrode tab lead 5 and the negative electrode current collector 21, or a resin member 7 may be provided both between the positive electrode tab lead 4 and the positive electrode current collector 11, and between the negative electrode tab lead 5 and the negative electrode current collector 21.

[0050] This specification includes at least the following: The components and other elements corresponding to those in the embodiments described above are shown in parentheses as examples, but are not limited thereto.

[0051] (1) An electrode laminate (electrode laminate 2) in which multiple positive electrode layers (positive electrode layer 10) and multiple negative electrode layers (negative electrode layer 20) are stacked via an electrolyte layer (solid electrolyte layer 30), A secondary battery (secondary battery 1) comprising an outer casing (outer casing 3) that houses the electrode stack, Tab leads (positive electrode tab lead 4, negative electrode tab lead 5) protruding from the outer casing are attached to the current collector of the positive electrode layer and the current collector of the negative electrode layer (positive electrode current collector 11, negative electrode current collector 21). A resin member (resin member 7) capable of interrupting overcurrent in response to rising temperature is bonded between the current collector of at least one of the positive electrode layer and the negative electrode layer and the tab lead. Secondary battery.

[0052] According to (1), a resin member capable of interrupting overcurrent in response to temperature rise is bonded between the current collector and the tab lead. For example, if the secondary battery becomes hot, the overcurrent that flows during charging and discharging of the secondary battery can be interrupted. Therefore, the safety of the secondary battery can be improved.

[0053] (2) A secondary battery as described in (1), The aforementioned resin member is a PTC element. Secondary battery.

[0054] According to (2), since the resin component is a PTC element, the electrical resistance of the PTC element increases when the temperature rises, thus ensuring a high current interruption effect.

[0055] (3) A secondary battery as described in (1) or (2), The current collector, the resin member, and the tab lead are joined by ultrasonic bonding. Secondary battery.

[0056] According to (3), by joining the current collector, resin member, and tab lead by ultrasonic bonding, the electrical influence at room temperature in the joint can be reduced. In addition, the adhesion at the joint can be improved.

[0057] (4) A secondary battery as described in any of (1) to (3), The current collector is joined to both sides of the tab lead via the resin member. Secondary battery.

[0058] According to (4), by joining current collectors to both sides of the tab lead, the number of current collectors at one joining point can be reduced, thus enabling good bonding between the current collector and the tab lead via the resin member.

[0059] (5) A secondary battery as described in (4), The resin member has an extended portion (extended portion 7a) that extends from the joint with the tab lead toward the electrode laminate. Secondary battery.

[0060] According to (5), since the resin member has an extension that extends from the joint with the tab lead toward the electrode laminate, it is possible to prevent the current collector from being biased toward one side in the thickness direction of the electrode laminate relative to the tab lead. Therefore, the current collector can be positioned in a balanced manner relative to the tab lead.

[0061] (6) A secondary battery as described in (5), The resin member is provided only in the central part of the current collector in the width direction of the current collector to be joined. Secondary battery.

[0062] According to (6), the weight of the resin member can be reduced compared to the case where the resin member is provided to the end in the width direction of the current collector. In addition, the contact area between the resin member and the current collector can be reduced, thereby reducing the effects of unnecessary contact.

[0063] (7) A secondary battery as described in any of (1) to (6), The resin member is bonded between the current collector and the tab lead of the positive electrode layer. Secondary battery.

[0064] According to (7), since the resin component is provided on the positive electrode side, overcurrent can be interrupted on the positive electrode side, further improving safety. [Explanation of Symbols]

[0065] 1 Secondary battery 2-electrode stack 3. Exterior 7 Resin components 7a Extension 10 Positive electrode layer 20 Negative electrode layer 30 Solid electrolyte layer (electrolyte layer)

Claims

1. An electrode laminate in which multiple positive electrode layers and multiple negative electrode layers are stacked with an electrolyte layer in between, A secondary battery comprising an outer casing that houses the electrode stack, Tab leads protruding from the outer casing are attached to the current collector of the positive electrode layer and the current collector of the negative electrode layer. A resin member capable of interrupting overcurrent in response to temperature increases is bonded between the current collector of at least one of the positive electrode layer and the negative electrode layer and the tab lead. Secondary battery.

2. A secondary battery according to claim 1, The aforementioned resin member is a PTC element. Secondary battery.

3. A secondary battery according to claim 1, The current collector, the resin member, and the tab lead are joined by ultrasonic bonding. Secondary battery.

4. A secondary battery according to any one of claims 1 to 3, The current collector is joined to both sides of the tab lead via the resin member. Secondary battery.

5. A secondary battery according to claim 4, The resin member has an extension portion that extends toward the electrode laminate from the joint with the tab lead. Secondary battery.

6. A secondary battery according to claim 5, The resin member is provided only in the central part of the current collector in the width direction of the current collector to be joined. Secondary battery.

7. A secondary battery according to any one of claims 1 to 3, The resin member is bonded between the current collector and the tab lead of the positive electrode layer. Secondary battery.

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