Monopolar electrodes and batteries

Abstract

To provide a monopolar electrode that can improve the gas emission properties and energy density in a battery as a primary object.SOLUTION: A monopolar electrode having a current collector and active material layers disposed on both surfaces of the current collector in the thickness direction is provided in the present disclosure. When the monopolar electrode is viewed in plan from the thickness direction, the current collector has a cutout portion, and the cutout portion has an opening, a space portion extending in a first direction corresponding to an inner direction of the current collector from the opening, and a bottom portion corresponding to an inner end portion of the space portion. When the length of the current collector in the first direction is L1A and the length of the cutout portion in the first direction is L1B, a ratio of L1B to L1A is 0.5 or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to monopolar electrodes and batteries. [Background technology]

[0002] It is known that a monopolar electrode is used in batteries, in which active material layers of the same polarity are disposed on both sides of a current collector. In the field of batteries, a technology has been investigated for discharging gas generated from the active material layer during charging and discharging of the battery to the outside of the electrode or the battery.

[0003] For example, Patent Document 1 discloses an electricity storage device including a separator layer disposed between active material layers and an adhesive layer disposed between the active material layers and the separator layer, wherein grooves are formed on the surface of the active material layer. Patent Document 2 also discloses a battery module in which prismatic batteries and separators are stacked along the arrangement direction, and the separator has grooves on the surface facing the prismatic batteries. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-026679 [Patent Document 2] Japanese Patent Publication No. 2022-092269 Summary of the Invention [Problem to be solved by the invention]

[0005] As in Patent Document 1 mentioned above, when grooves are provided on the surface of the active material layer, gas discharge properties are improved, but the volume of the active material layer is reduced, which may result in a decrease in the volumetric efficiency of the battery (the battery's energy density per volume).

[0006] The present disclosure has been made in view of the above circumstances, and has as its main object to provide a monopolar electrode that can improve gas discharge properties and energy density in a battery. [Means for solving the problem]

[0007] [1] A monopolar electrode having a current collector and active material layers disposed on both sides of the current collector in a thickness direction, wherein, when the monopolar electrode is viewed from above in the thickness direction, the current collector has a notch, the notch has an opening, a space extending from the opening in a first direction corresponding to an inward direction of the current collector, and a bottom corresponding to an inner end of the space, and the length of the current collector in the first direction is defined as L 1A The length of the notch in the first direction is L 1B In this case, the above L 1A The above L 1B The ratio is 0.5 or more, monopolar electrodes.

[0008] [2] In the plan view, the length of the current collector in a second direction perpendicular to the first direction is defined as L 2A The length of the notch in the second direction is L 2B In this case, the above L 2A The above L 2B The monopolar electrode according to [1], wherein the ratio is 0.02 or more.

[0009] [3] The monopolar electrode according to [1] or [2], wherein, in the plan view, the first direction is parallel to a longitudinal direction of the current collector.

[0010] [4] The monopolar electrode according to [1] or [2], wherein, in the plan view, the first direction is parallel to a short-side direction of the current collector.

[0011] [5] The monopolar electrode according to any one of [1] to [4], wherein the current collector has a plurality of the notches in a second direction perpendicular to the first direction.

[0012] [6] A battery having a first monopolar electrode, a second monopolar electrode having a polarity opposite to that of the first monopolar electrode, and a separator disposed between the first monopolar electrode and the second monopolar electrode, wherein at least one of the first monopolar electrode and the second monopolar electrode is a monopolar electrode according to any one of [1] to [5]. [Effects of the Invention]

[0013] The present disclosure has an effect of providing a monopolar electrode that can improve gas discharge properties and energy density in a battery. [Brief explanation of the drawings]

[0014] [Figure 1] 1A and 1B are schematic side and plan views illustrating a monopolar electrode according to the present disclosure. [Figure 2] 1A and 1B are schematic side and plan views illustrating a monopolar electrode according to the present disclosure. [Figure 3] FIG. 1 is a schematic plan view illustrating a monopolar electrode according to the present disclosure. [Figure 4] FIG. 1 is a schematic plan view illustrating a monopolar electrode according to the present disclosure. [Figure 5] FIG. 1 is a schematic side view illustrating a battery according to the present disclosure. [Figure 6] FIG. 1 is a diagram showing the results of examples and comparative examples in the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] The monopolar electrode and battery of the present disclosure will be described in detail below. The following drawings are schematic illustrations, and the size and shape of each part are appropriately exaggerated for ease of understanding. Furthermore, in this specification, when describing an arrangement of another member relative to a certain member, the term "above" or "below" simply refers to both an arrangement of another member directly above or below the certain member, so as to be in contact with the certain member, and an arrangement of another member above or below the certain member via another member, unless otherwise specified.

[0016] Here, the portion of the current collector other than the notched portion is referred to as a non-notched portion.

[0017] A. Monopolar electrode 1 and 2 are schematic side and plan views illustrating a monopolar electrode according to the present disclosure. Specifically, Fig. 1(a) and Fig. 2(a) are schematic side views of the monopolar electrode viewed from the opening side of the cutout, and Fig. 1(b) and Fig. 2(b) are schematic plan views of the monopolar electrode viewed from the thickness direction. Note that the active material layer is omitted in Fig. 1(b) and Fig. 2(b).

[0018] As shown in FIGS. 1(a) and 2(a), the monopolar electrode 10 includes a current collector 1 and active material layers 2 disposed on both surfaces (P, Q) of the current collector 1 in the thickness direction z. As shown in FIGS. 1(b) and 2(b), when the monopolar electrode 10 is viewed from above in the thickness direction z, the current collector 1 includes a notch S. The notch S includes an opening Sa, a space Sc extending from the opening Sa in a first direction x corresponding to the interior of the current collector 1, and a bottom Sb corresponding to the inner edge of the space Sc. The length of the current collector 1 in the first direction x is defined as L. 1A The length of the cutout portion S in the first direction x is L 1B In this case, L 1A L for 1B The ratio is 0.5 or more.

[0019] According to the present disclosure, the current collector has a predetermined notch, which results in a monopolar electrode that can improve gas discharge properties and energy density in a battery.

[0020] In the monopolar electrode of the present disclosure, the cutouts are provided in the current collector rather than in the active material layer, allowing the amount of active material layer to be maintained, improving the volumetric efficiency of a battery using the monopolar electrode. As shown in the examples described below, there is a concern that gas escape may be impaired in areas distant from the electrode's edges, such as the center of the electrode. In contrast, in the monopolar electrode of the present disclosure, the ratio of the length of the cutouts to the length of the current collector in the first direction is 0.5 or greater, so that a cutout serving as a gas escape path is also provided in the center of the electrode. As a result, the gas escape of a battery using the monopolar electrode can be improved.

[0021] 1. Current collector As shown in Figures 1(b) and 2(b), when viewed in plan from the thickness direction z, the current collector 1 according to the present disclosure has a cutout portion S having an opening Sa, a space Sc extending in a first direction x, and a bottom Sb. In the plan view, the first direction x may be parallel to the longitudinal direction of the current collector 1 (Figure 1(b)) or parallel to the lateral direction (Figure 2(b)). In this specification, "parallel" means that the angle between the two directions is 30° or less.

[0022] Here, the length of the current collector 1 in the first direction x is L 1A The length of the cutout portion S in the first direction x is L 1B Let's say. L 1A L for 1B The ratio (L 1B / L 1A ) is 0.5 or more, may be 0.6 or more, or may be 0.7 or more. 1B / L 1A is usually less than 1.0, and may be 0.9 or less, or may be 0.8 or less. Here, the length of the cutout portion can be considered as the length from the opening to the bottom of the space portion.

[0023] In addition, in the plan view, the length of the current collector 1 in the second direction y perpendicular to the first direction x is defined as L 2A The length of the cutout portion S in the second direction y is L 2B In this case, L 2A L for 2B The ratio (L 2B / L 2A ) is, for example, 0.02 or more, may be 0.05 or more, or may be 0.1 or more. 2B / L 2A is, for example, 0.5 or less, may be 0.4 or less, or may be 0.3 or less.

[0024] As shown in FIG. 1(b), the current collector 1 may have one notch S. On the other hand, as shown in FIG. 2(b), the current collector 1 may have multiple notches (S1 to S3) in a second direction y perpendicular to the first direction x. When the current collector has multiple notches, the number of the notches may be 3 or more, or may be 5 or more. In the multiple notches, 1B / L 1A and L 2B / L 2A may be the same or different.

[0025] Furthermore, when the current collector has a plurality of cutouts, as shown in FIG. 3, the cutouts may include cutouts Sα and Sβ that extend in opposite directions from the opening Sa toward the bottom Sb.

[0026] As shown in FIGS. 1(a) and 2(a), the cutout portion S typically penetrates the current collector 1 in the thickness direction z. When the monopolar electrode 10 is viewed from above in the thickness direction, as shown in FIG. 4, the entire cutout portion S and the entire non-cutout portion (the entire current collector 1) may overlap with the active material layer 2 (FIG. 4(a)), or a portion of the cutout portion S and a portion of the non-cutout portion may overlap with the active material layer 2 (FIG. 4(b)). Although not specifically shown, the entire cutout portion may overlap with the active material layer, and a portion of the non-cutout portion may overlap with the active material layer.

[0027] In the plan view, the ratio of the area of ​​the cutout portion to the area of ​​the current collector is not particularly limited, but is, for example, 0.1 to 0.5. When the current collector has multiple cutout portions, the area of ​​the cutout portion refers to the total area of ​​the multiple cutout portions.

[0028] The shape of the cutout portion in the plan view (planar shape of the cutout portion) is not particularly limited, and may be a rectangle such as a square, or a circle such as a semi-ellipse. The planar shape of the current collector is typically a square, but is not limited thereto.

[0029] As shown in Figures 1(a), 2(a), and 4, active material layers are typically disposed above and below the cutouts in the thickness direction (above and below all or part of the cutouts). In other words, the cutouts in the current collector are typically not filled with active material layers. Therefore, the cutouts in the current collector can be considered as holes that connect the inside and outside of the monopolar electrode.

[0030] The material of the current collector is not particularly limited, and may be any conventional material used as a positive electrode current collector or a negative electrode current collector. Examples of the material of the positive electrode current collector include Al, SUS, and Ni. Examples of the material of the negative electrode current collector include Cu, SUS, and Ni. The thickness of the current collector is not particularly limited.

[0031] 2.Active material layer As shown in Figures 1(a) and 2(a), active material layers 2 are disposed on both surfaces (P, Q) of a current collector 1 in the thickness direction z. In a monopolar electrode, the two active material layers have the same polarity.

[0032] The active material layer contains at least an active material. When the active material layer is a positive electrode active material layer, the active material is a positive electrode active material. Typical examples of the positive electrode active material include oxide active materials. Examples of oxide active materials include LiCoO2, LiMnO2, LiNiO2, LiVO2, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc., rock salt layered active materials, LiMn2O4, Li(Ni0.5Mn 1.5 )O4, and olivine type active materials such as LiFePO4, LiMnPO4, LiNiPO4, and LiCuPO4.

[0033] When the active material layer is a negative electrode active material layer, the active material is a negative electrode active material. Examples of the negative electrode active material include carbon active materials, oxide active materials, and metal active materials. Examples of the carbon active material include mesocarbon microbeads (MCMB), highly oriented graphite (HOPG), hard carbon, and soft carbon. Examples of the oxide active material include Nb2O5, Li4Ti5O 12 and SiO. Examples of metal active materials include In, Al, Si, and Sn.

[0034] The active material layer may also contain at least one conductive material and binder, as needed. Examples of conductive materials include carbon materials, metal particles, and conductive polymers. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and ketjen black (KB); and fibrous carbon materials such as carbon fiber, carbon nanotubes (CNT), and carbon nanofibers (CNF). Examples of binders include fluorine-containing binders such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE), rubber-based binders such as butadiene rubber, and acrylic binders.

[0035] 3. Monopolar Electrodes The monopolar electrode in the present disclosure may be a positive electrode or a negative electrode. That is, the current collector described above may be a positive electrode current collector or a negative electrode current collector. Furthermore, the active material layer described above may be a positive electrode active material layer or a negative electrode active material layer.

[0036] The monopolar electrode of the present disclosure can be manufactured, for example, by the following method. First, a metal foil (current collector) is prepared, with its short side aligned in a first direction and its long side aligned in a second direction perpendicular to the first direction. The metal foil is then cut using, for example, a blade and a laser to obtain a current collector with the aforementioned cutout. A core insert, adjusted to the same thickness as the current collector, is inserted into the cutout. The surface of the core insert is preferably subjected to a surface treatment such as hard chrome plating or DLC (Diamond-Like Carbon) coating. This weakens the bond with the active material layer, making it easier for the active material layer to peel off from the core insert when the core insert is removed after pressing, as described below, and thus reducing the risk of chipping of the active material layer.

[0037] Next, while the current collector is being transported in the second direction, a composite containing at least an active material is applied to the current collector and pressed to form the active material layer. The insert is then pulled out to obtain a monopolar electrode having a transverse direction in the first direction and the notch described above. Cutting the monopolar electrode having a transverse direction in the first direction (a monopolar electrode having a longitudinal direction in the second direction) can also produce a monopolar electrode having a longitudinal direction in the first direction.

[0038] B.Battery FIG. 5 is a schematic side view illustrating a battery according to the present disclosure. The battery shown in FIG. 5 is a stacked battery in which multiple monopolar electrodes are stacked in the thickness direction with separators interposed therebetween. FIG. 5 is also a schematic side view of the stacked battery as viewed from the cutout opening side. The battery 100 shown in FIGS. 5(a) and 5(b) includes a first monopolar electrode 10A, a second monopolar electrode 10B having the opposite polarity to the first monopolar electrode 10A, and a separator 20 disposed between the first monopolar electrode 10A and the second monopolar electrode 10B. The first monopolar electrode 10A and the second monopolar electrode 10B each include active material layers (2A, 2B) disposed on both sides of a current collector (1A, 1B). For example, the first monopolar electrode 10A is a positive electrode, and the second monopolar electrode 10B is a negative electrode. In the battery of the present disclosure, at least one of the first monopolar electrode and the second monopolar electrode is the monopolar electrode (monopolar electrode having a notch) described above. As shown in FIG. 5(a), in the battery 100, both the first monopolar electrode 10A and the second monopolar electrode 10B may be the monopolar electrode described above in the present disclosure. As shown in FIG. 5(b), only the first monopolar electrode 10A may be the monopolar electrode described above in the present disclosure. Although not specifically shown, only the second monopolar electrode 10B may be the monopolar electrode described above.

[0039] In the battery of the present disclosure, at least one of the first monopolar electrode and the second monopolar electrode is the monopolar electrode described above, and therefore the battery has good gas discharge properties and energy density.

[0040] The first monopolar electrode and the second monopolar electrode are electrodes of opposite polarity, i.e., positive or negative. The positive and negative electrodes are the same as those described in "A. Monopolar Electrodes," so a description thereof will be omitted here.

[0041] The separator is a member disposed between the first monopolar electrode and the second monopolar electrode. The material of the separator is not particularly limited as long as it is a porous membrane, and examples thereof include resins such as polyethylene (PE). The separator may have a single-layer structure or a multi-layer structure. The separator may be made of nonwoven fabric such as a resin nonwoven fabric or a glass fiber nonwoven fabric.

[0042] The battery in the present disclosure may be a stacked battery in which a first monopolar electrode, a separator, and a second monopolar electrode are stacked in the thickness direction, or a wound battery in which a first monopolar electrode, a separator, and a second monopolar electrode are wound, but the former is preferred.

[0043] The battery in this disclosure is typically a liquid-based battery containing a liquid electrolyte (electrolytic solution) as an electrolyte. The electrolytic solution contains a non-aqueous solvent and a supporting salt. Examples of the non-aqueous solvent include organic solvents such as carbonates, ethers, esters, nitriles, sulfones, and lactones. Examples of the supporting salt include lithium salts such as LiPF6.

[0044] The battery in the present disclosure is typically a lithium-ion secondary battery. Examples of uses of the battery include power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), electric vehicles (BEVs), gasoline-powered vehicles, and diesel-powered vehicles. It is particularly preferred that the battery be used as a driving power source for hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or electric vehicles (BEVs). The battery in the present disclosure may also be used as a power source for mobile objects other than vehicles (e.g., trains, ships, and aircraft), or as a power source for electrical appliances such as information processing devices.

[0045] The present disclosure is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any configuration that is substantially identical to the technical idea described in the claims of the present disclosure and that provides similar effects is included within the technical scope of the present disclosure. [Example]

[0046] [Examples and Comparative Examples] Using CAE (Computer Aided Engineering), a monopolar electrode (Comparative Example) in which the current collector does not have a notch and a monopolar electrode (Example) in which the current collector has a notch were created, and the gas generation and gas movement phenomena in the electrode were simulated. The results are shown in Figure 6. The size of the notch in the Example was L 1B / L 1A = 0.5.

[0047] As shown in Figure 6(a), when no notches were provided, the gas density was highest at the center of the electrode and decreased from the center to the edge. On the other hand, as shown in Figure 6(b), when a specified notch was provided, the gas density at the center of the electrode decreased significantly, and the gas density distribution changed. Furthermore, the maximum gas density was also lower than in the comparative example.

[0048] This demonstrates that the monopolar electrode of the present disclosure can improve gas discharge properties and energy density in a battery. [Explanation of symbols]

[0049] 1...Current collector 2...Active material layer 10...Monopolar electrode 10A...First monopolar electrode 10B...Second monopolar electrode 20...Separator 100...battery

Claims

1. A monopolar electrode for use in a wound-type battery, comprising: the monopolar electrode has a current collector and active material layers disposed on both sides of the current collector in a thickness direction, When the monopolar electrode is viewed in plan from the thickness direction, the current collector has a notch, the notch portion has an opening, a space portion extending from the opening in a first direction corresponding to an inward direction of the current collector, and a bottom portion corresponding to an inner end of the space portion, The length of the current collector in the first direction is L １Ａ and the length of the notch in the first direction is L １Ｂ In this case, the L １Ａ The L １Ｂ is 0.5 or more, In the plan view, the first direction is parallel to a short-side direction of the current collector.

2. In the plan view, when the length of the current collector in a second direction perpendicular to the first direction is L2A and the length of the cutout portion in the second direction is L2B, The monopolar electrode of claim 1 , wherein the ratio of L 2B to L 2A is greater than or equal to 0.

02.

3. The monopolar electrode according to claim 1 , wherein the current collector has a plurality of the notches in a second direction perpendicular to the first direction.

4. A battery having a first monopolar electrode, a second monopolar electrode having an opposite polarity to the first monopolar electrode, and a separator disposed between the first monopolar electrode and the second monopolar electrode, the battery is a wound type battery in which the first monopolar electrode, the separator, and the second monopolar electrode are wound together, A battery, wherein at least one of the first monopolar electrode and the second monopolar electrode is the monopolar electrode according to any one of claims 1 to 3.

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