Monopolar electrode and battery

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 having the same polarity are disposed on both sides of a current collector. In the field of batteries, a technology is being studied 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 layer and the separator layer, the active material layer having a groove formed on the surface thereof. Patent Document 2 discloses a battery module in which prismatic batteries and separators are stacked in the arrangement direction, the separator having a groove on the surface facing the prismatic batteries. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2022-026679 [Patent Document 2] 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, the gas discharge properties are improved, but the volume of the active material layer is reduced, which may reduce the volumetric efficiency of the battery (the battery's energy density per volume).

[0006] The present disclosure has been made in consideration of the above-mentioned 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 in plan 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 inner 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 cutout portion in the first direction is L 1B In this case, the above L 1A The above L 1B The ratio of is 0.5 or more for 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 cutout portion 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 cutouts in a second direction perpendicular to the first direction.

[0012] [6] 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, 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]. Effect 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 description of the drawings]

[0014] [Figure 1] 1A and 1B are schematic side and plan views illustrating a monopolar electrode according to the present disclosure. [Diagram 2] 1A and 1B are schematic side and plan views illustrating a monopolar electrode according to the present disclosure. [Diagram 3] FIG. 2 is a schematic plan view illustrating a monopolar electrode in the present disclosure. [Figure 4] FIG. 2 is a schematic plan view illustrating a monopolar electrode in the present disclosure. [Diagram 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 PREFERRED EMBODIMENTS

[0015] The monopolar electrode and the battery in the present disclosure will be described in detail below. Each of the figures shown below is a schematic illustration, and the size and shape of each part are appropriately exaggerated to facilitate understanding. In addition, in this specification, when expressing an aspect in which another member is arranged relative to a certain member, the term "above" or "below" is used, unless otherwise specified, it includes both a case in which another member is arranged directly above or below a certain member so as to be in contact with the certain member, and a case in which another member is arranged above or below a certain member via another member.

[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 Figures 1 and 2 are schematic side and plan views illustrating the monopolar electrode of the present disclosure. Specifically, Figures 1(a) and 2(a) are schematic side views of the monopolar electrode as viewed from the opening side of the cutout portion, and Figures 1(b) and 2(b) are schematic plan views of the monopolar electrode as viewed from the thickness direction. Note that the active material layer is omitted in Figures 1(b) and 2(b).

[0018] As shown in Figs. 1(a) and 2(a), the monopolar electrode 10 has a current collector 1 and active material layers 2 disposed on both sides (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 in plan from the thickness direction z, the current collector 1 has a notch S. The notch S has an opening Sa, a space Sc extending from the opening Sa in a first direction x corresponding to the inner direction of the current collector 1, and a bottom Sb corresponding to the inner end 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, since the current collector has a predetermined cutout portion, a monopolar electrode can be formed that can improve gas discharge properties and energy density in a battery.

[0020] In the monopolar electrode of the present disclosure, the cutout portion is provided in the current collector, not in the active material layer, so that the amount of the active material layer can be maintained, and the volume efficiency of the battery using the monopolar electrode can be improved. Here, as shown in the examples described later, there is a concern that the gas escape property may be reduced in a portion distant from the end of the electrode, such as the center portion of the electrode. In contrast, in the monopolar electrode of the present disclosure, the ratio of the length of the cutout portion to the length of the current collector in the first direction is 0.5 or more, so that the cutout portion, which is a gas escape path, is also provided in the center portion of the electrode. As a result, the gas escape property of the 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 of the present disclosure has a cutout portion S having an opening Sa, a space portion Sc extending in a first direction x, and a bottom portion 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 us assume that L 1A L for 1B Percentage of (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 portion to the bottom portion 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 Percentage of (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 cutout portion S. On the other hand, as shown in FIG. 2(b), the current collector 1 may have multiple cutout portions (S1 to S3) in a second direction y perpendicular to the first direction x. When the current collector has multiple cutout portions, the number of the cutout portions may be 3 or more, or may be 5 or more. In the multiple cutout portions, the above L 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 Fig. 1(a) and Fig. 2(a), the cutout portion S usually penetrates the current collector 1 in the thickness direction z. When the monopolar electrode 10 is viewed in plan 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 part of the cutout portion S and a part of the non-cutout portion may overlap with the active material layer 2 (Fig. 4(b)). Although not particularly shown, the entire cutout portion may overlap with the active material layer, and a part 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] Here, as shown in Figures 1(a), 2(a) and 4, active material layers are usually arranged 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 usually not filled with active material layers. Therefore, the cutouts in the current collector can be regarded as holes that communicate between the inside and outside of the monopolar electrode.

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

[0031] 2.Active material layer 1(a) and 2(a), active material layers 2 are disposed on both faces (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. The positive electrode active material is typically an oxide active material. Examples of the oxide active material 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 the like; 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 material, oxide active material, and metal active material. 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. Metal active materials include, for example, In, Al, Si, and Sn.

[0034] The active material layer may contain at least one of a conductive material and a binder, if necessary. 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 fibers, 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. Also, 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) having a short side in a first direction and a long side in a second direction perpendicular to the first direction is prepared. Then, the metal foil is cut using, for example, a blade and a laser to obtain a current collector having the above-mentioned notch. In addition, a core insert adjusted to the same thickness as the current collector is inserted into the notch. The surface of the core insert is preferably surface-treated by hard chrome plating and DLC (Diamond-Like Carbon) coating. Since the bond with the active material layer can be weakened, the active material layer is easily peeled off from the core insert when the core insert is pulled out after pressing as described below, and chipping of the active material layer can be suppressed.

[0037] Next, while the current collector is transported in the second direction, a composite material containing at least an active material is applied onto the current collector and pressed to form the active material layer. The insert is then pulled out to obtain a monopolar electrode having a short side in the first direction and the above-mentioned cutout portion. Note that a monopolar electrode having a long side in the first direction can be obtained by cutting the monopolar electrode having a short side in the first direction (a monopolar electrode having a long side in the second direction).

[0038] B.Battery FIG. 5 is a schematic side view illustrating a battery in the present disclosure. The battery shown in FIG. 5 is a stacked battery in which a plurality of monopolar electrodes are stacked in the thickness direction with a separator interposed therebetween. FIG. 5 is a schematic side view of the stacked battery as viewed from the opening side of the cutout portion. The battery 100 shown in FIGS. 5(a) and (b) has a first monopolar electrode 10A, a second monopolar electrode 10B having a polarity opposite to that of 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 have active material layers (2A, 2B) disposed on both sides of the 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 of the present disclosure described above, or as shown in FIG. 5(b), only the first monopolar electrode 10A may be the monopolar electrode of the present disclosure described above. Although not particularly 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 having opposite polarities, i.e., positive and negative electrodes. The positive and negative electrodes are the same as those described in "A. Monopolar electrodes", so the description here is omitted.

[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 film, 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 a 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 type battery in which a first monopolar electrode, a separator, and a second monopolar electrode are stacked in the thickness direction, or a wound type battery in which a first monopolar electrode, a separator, and a second monopolar electrode are wound, with the former being preferred.

[0043] The battery in the present disclosure is typically a liquid-based battery that contains a liquid electrolyte (electrolytic solution) as an electrolyte. The electrolytic solution contains a non-aqueous solvent and a supporting salt. The non-aqueous solvent may be an organic solvent such as carbonates, ethers, esters, nitriles, sulfones, lactones, etc. The supporting salt may be a lithium salt such as LiPF6, for example.

[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 automobiles, and diesel automobiles. In particular, the battery is preferably 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 moving objects other than vehicles (for example, railways, ships, and aircraft), and may also be used as a power source for electrical products such as information processing devices.

[0045] The present disclosure is not limited to the above-described embodiment. The above-described embodiment is merely an example, and any configuration that is substantially the same as the technical idea described in the claims of the present disclosure and that exhibits similar effects is included in the technical scope of the present disclosure. EXAMPLES

[0046] [Examples and Comparative Examples] Using CAE (Computer Aided Engineering), a monopolar electrode in which the current collector does not have a notch (Comparative Example) and a monopolar electrode in which the current collector has a notch (Example) were created, and the gas generation and gas movement phenomena in the electrodes 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 Fig. 6(a), when no cutout was provided, the gas density was maximum at the center of the electrode, and the gas density decreased from the center to the edge of the electrode. On the other hand, as shown in Fig. 6(b), when a certain cutout was provided, the gas density at the center of the electrode decreased significantly, and the gas density distribution changed. In addition, the maximum gas density was also decreased compared to the comparative example.

[0048] This demonstrates that the monopolar electrode of the present disclosure can provide good 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 having a current collector and an active material layer disposed on each of both sides of the current collector in a thickness direction, When the monopolar electrode is viewed in a plan view from the thickness direction, The current collector has a notch, the cutout portion has an opening, a space portion extending in a first direction corresponding to a direction toward the inside of the current collector from the opening, and a bottom portion corresponding to an inner end portion of the space portion, The length of the current collector in the first direction is L １Ａ and the length of the cutout portion in the first direction is L １Ｂ In this case, the L １Ａ The above L １Ｂ is 0.5 or greater.

2. In the plan view, the length of the current collector in a second direction perpendicular to the first direction is L ２Ａ and the length of the cutout portion in the second direction is L ２Ｂ In this case, Said L ２Ａ The above L ２Ｂ 2. The monopolar electrode of claim 1 , wherein the ratio is 0.02 or greater.

3. The monopolar electrode according to claim 1 , wherein in the plan view, the first direction is parallel to a longitudinal direction of the current collector.

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

5. 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.

6. 1. 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, A battery, wherein at least one of the first monopolar electrode and the second monopolar electrode is a monopolar electrode according to any one of claims 1 to 5.

Images