Separator and power storage device including the separator

Abstract

To provide a technique for obtaining a power storage device in which the impregnability of the electrolyte is suitably improved.SOLUTION: Separators 70 are used in a battery 100. The battery 100 includes: an electrode body 20 having a positive and negative electrode stacking structure A in which a positive electrode 50 and a negative electrode 60 are stacked via the separator 70; a battery case 30 for housing the electrode body 20; and an electrolyte. The separator 70 has a plurality of grooves 72 extending from one end 70A of the separator 70 constituting one of the positive and negative electrode stacked structure A along a direction towards the other end 70B.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a separator and a power storage device including the separator.

Background Art

[0002] In recent years, batteries such as lithium-ion secondary batteries have been suitably used as portable power sources for personal computers, mobile terminals, etc., and power sources for driving vehicles such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc. Such a battery typically includes an electrode body in which a positive electrode and a negative electrode are laminated via a separator, and an electrolyte. For example, Patent Documents 1 and 2 below disclose such a battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, according to the study by the present inventors, it has been found that there is still room for improvement in power storage devices (for example, batteries) as described above from the viewpoint of improving the permeability of the electrolyte.

Means for Solving the Problems

[0005] The separator disclosed herein is a separator used in a power storage device including an electrode body having a positive-negative electrode laminate structure in which a positive electrode and a negative electrode are laminated via the separator, a case housing the electrode body, and an electrolyte, and has one or a plurality of groove portions extending along a direction from one end of the separator constituting one positive-negative electrode laminate structure toward the other end. Although details will be described later, according to the separator having such a configuration, it is possible to suitably improve the impregnation property of the electrolyte in the power storage device.

[0006] Also, from another aspect, the present disclosure provides a power storage device. Such a power storage device is a power storage device including an electrode body in which a positive electrode and a negative electrode are laminated via a separator, a case housing the electrode body, and an electrolyte, wherein the separator is any of the separators disclosed herein. Since such a power storage device includes any of the separators disclosed herein, the impregnation property of the electrolyte is suitably improved.

Brief Description of the Drawings

[0007]

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Embodiments for Carrying Out the Invention

[0008] Hereinafter, some embodiments of the technology disclosed herein will be described with reference to the drawings. Note that matters other than those specifically mentioned in this specification and necessary for the implementation of the technology disclosed herein (for example, general configurations and manufacturing processes of batteries that do not characterize the present invention) can be grasped as design matters of those skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common general knowledge in the relevant field. Note that the notation "A to B" indicating a range in this specification means "A or more and B or less". Also, it is intended to include the meanings of "exceeding A" and "less than B".

[0009] Note that in this specification, the "power storage device" refers to a device that can perform charging and discharging. Power storage devices include batteries such as primary batteries and secondary batteries (for example, lithium-ion secondary batteries and nickel-metal hydride batteries), and capacitors (physical batteries) such as electric double layer capacitors. Further, the electrolyte may be either a liquid electrolyte (electrolyte solution) or a gel electrolyte.

[0010] <Configuration of the Battery> Hereinafter, this technology will be described by taking a lithium-ion secondary battery, which is an embodiment of the energy storage device disclosed herein, as an example.

[0011] The lithium-ion secondary battery shown in FIG. 1 (hereinafter, also simply referred to as "battery 100") is a sealed battery constructed by accommodating an electrode body 20, which is a flat wound electrode body, and an electrolytic solution (not shown) in a flat rectangular battery case (i.e., an exterior container) 30. The battery case 30 is provided with a positive electrode terminal 42 and a negative electrode terminal 44 for external connection, and a thin safety valve 36 configured to release the internal pressure of the battery case 30 when the internal pressure thereof rises to a predetermined level or higher. The positive and negative electrode terminals 42 and 44 are electrically connected to positive and negative electrode current collectors 42a and 44a, respectively. As the material of the battery case 30, for example, a lightweight and highly thermally conductive metal material such as aluminum is used.

[0012] As shown in FIGS. 1 and 2, the electrode body 20 has a configuration in which a positive electrode 50 and a negative electrode 60 are overlapped via two long separator 70s and wound in the longitudinal direction. The positive electrode 50 has a configuration in which a positive electrode active material layer 54 is formed along the longitudinal direction on one side or both sides (here, both sides) of a long positive electrode current collector 52. The negative electrode 60 has a configuration in which a negative electrode active material layer 64 is formed along the longitudinal direction on one side or both sides (here, both sides) of a long negative electrode current collector 62. The non-formed portion 52a of the positive electrode active material layer (i.e., the portion where the positive electrode current collector 52 is exposed without the formation of the positive electrode active material layer 54) and the non-formed portion 62a of the negative electrode active material layer (i.e., the portion where the negative electrode current collector 62 is exposed without the formation of the negative electrode active material layer 64) are formed so as to protrude outward from both ends in the winding axis direction (i.e., the width direction orthogonal to the longitudinal direction) of the electrode body 20. A positive electrode current collector 42a and a negative electrode current collector 44a are joined to the non-formed portion 52a of the positive electrode active material layer and the non-formed portion 62a of the negative electrode active material layer, respectively.

[0013] As the positive electrode current collector 52, a known positive electrode current collector used in a lithium ion secondary battery may be used. Examples thereof include a sheet or foil made of a metal having good conductivity (for example, aluminum, nickel, titanium, stainless steel, etc.). As the positive electrode current collector 52, an aluminum foil is preferred.

[0014] The dimensions of the positive electrode current collector 52 are not particularly limited and may be appropriately determined according to the battery design. When using an aluminum foil as the positive electrode current collector 52, its thickness is not particularly limited, but is, for example, 5 μm to 35 μm, preferably 7 μm to 20 μm.

[0015] The positive electrode active material layer 54 contains a positive electrode active material. Examples of the positive electrode active material include lithium nickel-based composite oxides (e.g., LiNiO2, etc.), lithium cobalt-based composite oxides (e.g., LiCoO2, etc.), lithium nickel cobalt manganese-based composite oxides (e.g., LiNiCoMnO2, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, etc.), lithium nickel cobalt aluminum-based composite oxides (e.g., LiNi 0.8 Co 0.15 Al 0.5 O2, etc.), lithium manganese-based composite oxides (e.g., LiMn2O4, etc.), lithium nickel manganese-based composite oxides (e.g., LiNi 0.5 Mn 1.5 O4, etc.) and other lithium transition metal composite oxides; lithium transition metal phosphate compounds (e.g., LiFePO4, etc.).

[0016] The positive electrode active material layer 54 may contain components other than the positive electrode active material, such as trilithium phosphate, a conductive material, a binder, etc. As the conductive material, carbon black such as acetylene black (AB) and other carbon materials (e.g., graphite, etc.) can be preferably used. As the binder, polyvinylidene fluoride (PVDF), etc. can be used.

[0017] The content of the positive electrode active material in the positive electrode active material layer 54 (i.e., the content of the positive electrode active material when the total mass of the positive electrode active material layer 54 is 100% by mass) is not particularly limited, but is preferably 70% by mass or more, more preferably 80% by mass or more and 97% by mass or less, and still more preferably 85% by mass or more and 96% by mass or less. The content of lithium tripolyphosphate in the positive electrode active material layer 54 is not particularly limited, but is preferably 1% by mass or more and 15% by mass or less, and more preferably 2% by mass or more and 12% by mass or less. The content of the conductive material in the positive electrode active material layer 54 is not particularly limited, but is preferably 1% by mass or more and 15% by mass or less, and more preferably 3% by mass or more and 13% by mass or less. The content of the binder in the positive electrode active material layer 54 is not particularly limited, but is preferably 1% by mass or more and 15% by mass or less, and more preferably 1.5% by mass or more and 10% by mass or less.

[0018] The thickness of the positive electrode active material layer 54 is not particularly limited, but is, for example, 10 μm to 300 μm, preferably 20 μm to 200 μm.

[0019] As the negative electrode current collector 62, a known negative electrode current collector used in a lithium ion secondary battery may be used. Examples thereof include a sheet or foil made of a metal having good conductivity (for example, copper, nickel, titanium, stainless steel, etc.). As the negative electrode current collector 62, a copper foil is preferred.

[0020] The dimensions of the negative electrode current collector 62 are not particularly limited and may be appropriately determined according to the design of the battery. When a copper foil is used as the negative electrode current collector 62, its thickness is not particularly limited, but is, for example, 5 μm to 35 μm, preferably 7 μm to 20 μm or less.

[0021] The negative electrode active material layer 64 contains a negative electrode active material. Examples of the negative electrode active material include carbon materials such as graphite and silicon materials.

[0022] The negative electrode active material layer 64 may contain components other than the negative electrode active material, such as a binder, a thickener, and the like. As the binder, for example, styrene butadiene rubber (SBR), polyvinylidene fluoride (PVDF), or the like can be used. As the thickener, for example, carboxymethyl cellulose (CMC) or the like can be used.

[0023] The content of the negative electrode active material in the negative electrode active material layer 64 (that is, the content of the negative electrode active material when the total mass of the negative electrode active material layer 64 is 100% by mass) is not particularly limited, but is preferably 90% by mass or more, and more preferably 95% by mass or more and 99% by mass or less. The content of the binder in the negative electrode active material layer is preferably 0.1% by mass or more and 8% by mass or less, and more preferably 0.5% by mass or more and 3% by mass or less. The content of the thickener in the negative electrode active material layer is preferably 0.3% by mass or more and 3% by mass or less, and more preferably 0.5% by mass or more and 2% by mass or less.

[0024] The thickness of the negative electrode active material layer 64 is not particularly limited, but is, for example, 10 μm to 300 μm, and preferably 20 μm to 200 μm.

[0025] Subsequently, the separator 70 included in the battery 100 will be described in detail. Here, FIG. 4 is a schematic explanatory diagram for explaining the groove portion 72 of the separator 70 shown in FIG. 2. FIG. 5 is a schematic cross-sectional view in the thickness direction of the separator shown in FIG. 4. The separator 70 is a separator used in a battery including an electrode body 20 having a positive-negative electrode laminated structure A in which a positive electrode 50 and a negative electrode 60 are laminated via the separator 70, a battery case 30 that houses the electrode body 20, and an electrolyte (here, a liquid electrolyte). As shown in FIGS. 2, 4 to 5, the separator 70 according to the present embodiment has a plurality (here, six) of groove portions 72 extending along the direction from the end portion 70A to the other end portion 70B of the separator 70 constituting one positive-negative electrode laminated structure A.

[0026] In a conventional battery, in the liquid injection process, it generally takes a long time to allow the electrolytic solution to penetrate throughout the inside of the electrode body. Also, if the time from liquid injection to the first charge becomes long, there is a risk of metal elution from the electrode current collector, which is not preferable. In contrast, in the present disclosure, as a separator constituting the battery 100, a separator 70 having one or a plurality of groove portions extending along the direction from the end portion 70A of the separator 70 constituting one positive / negative electrode laminate structure A of the electrode body 20 toward the other end portion 70B is used. Thereby, in the liquid injection process in the process of manufacturing the battery 100, it becomes possible to penetrate the electrolytic solution to the central region of the electrode body 20 in a short time. Specifically, when the electrolytic solution penetrates from the two end faces constituting the positive / negative electrode laminate structure A of the electrode body 20 toward the center (here, when the electrolytic solution penetrates from both end portions in the winding axis direction WD of the electrode body 20 toward the center), it penetrates so as to flow inside the groove portion 72 of the separator 70, and thus the electrolytic solution can be quickly penetrated. Therefore, according to the separator 70 having such a configuration, a highly reliable battery 100 with suitably improved impregnation property of the electrolytic solution can be obtained. Also, in the battery 100 provided with the separator 70, elution of metal from the electrode current collector as described above can be suitably suppressed. Furthermore, since the battery 100 provided with the separator 70 is a battery manufactured with the liquid injection process time shortened, it is also preferable from the viewpoint of manufacturing cost.

[0027] As shown in FIGS. 2 and 4, the groove portion 72 provided in the separator 70 according to the present embodiment is formed from one end portion 70A to the other end portion 70B of the separator 70. According to such a configuration, in the electrolyte injection step in the process of manufacturing the battery 100, it becomes possible to penetrate the electrolyte to the central region of the electrode body 20 in a shorter time. Specifically, between the two end faces from the center of the positive and negative electrode laminated structure A of the electrode body 20 to the center (here, between both ends in the winding axis direction WD of the electrode body 20 to the center), the electrolyte flows through the inside of the groove portion 72 of the separator 70 and penetrates, so that the electrolyte can be penetrated in a shorter time. However, in other embodiments, the groove portion 72 may be intermittently formed along the direction from the end portion 70A to the other end portion 70B of the separator 70. Alternatively, the groove portion 72 may be formed in a region (for example, the central region of the separator 70) excluding the end portion 70A and / or the other end portion 70B of the separator 70.

[0028] As shown in FIG. 4, in the present embodiment, six groove portions 72 are formed, but the present invention is not limited to this. In other embodiments, only one groove portion 72 may be formed, or a plurality of groove portions 72 other than six may be formed. Further, as shown in FIG. 4, in the present embodiment, the shape of the groove portion 72 in plan view is rectangular, but the present invention is not limited to this. For example, it can be various shapes such as those in the seventh to tenth embodiments described later. And, as shown in FIG. 5, in the present embodiment, the cross-sectional shape of the groove portion 72 is rectangular, but the present invention is not limited to this. For example, it can be various shapes such as those in the second to sixth embodiments described later.

[0029] Further, the depth (%) of the groove portion 72 of the separator 70 is not particularly limited as long as the effects of the technology disclosed herein are exhibited. Here, the depth (%) of the groove portion 72 means the ratio of the depth S of the groove portion 72 to the length P in the direction Y in which the groove portion 72 of the electrode body 20 is formed (here, the length P in the winding axis direction WD of the electrode body 20), that is, the value expressed by (S / P)×100 (%) (see FIGS. 3 and 5). The lower limit of the depth of the groove portion 72 is, from the viewpoint of improving the impregnation property of the electrolytic solution with respect to the electrode body 20, for example, 0.0005% or more, preferably 0.001% or more, more preferably 0.002% or more, and particularly preferably 0.003% or more. Also, the lower limit of the groove portion 72 is, from the viewpoint of suitably ensuring the strength of the separator 70, for example, 0.02% or less, preferably 0.01% or less (for example, 0.007% or less). However, it is not limited thereto.

[0030] Further, the width (%) of the groove portion 72 of the separator 70 is not particularly limited as long as the effects of the technology disclosed herein are exhibited. Here, the width (%) of the groove portion 72 means the ratio of the width R of the groove portion 72 to the length P in the direction Y in which the groove portion 72 of the electrode body 20 is formed (here, the length P in the winding axis direction WD of the electrode body 20), that is, the value expressed by (R / P)×100 (%) (see FIGS. 3 and 5). The lower limit of the width of the groove portion 72 is, from the viewpoint of improving the impregnation property of the electrolytic solution with respect to the electrode body 20, for example, 0.002% or more, preferably 0.0025% or more, more preferably 0.005% or more, and particularly preferably 0.0075% or more. Also, the lower limit of the groove portion 72 is, from the viewpoint of suitably ensuring the strength of the separator 70, for example, 0.05% or less, preferably 0.02% or less. However, it is not limited thereto.

[0031] Also, the distance (%) between the groove portions 72 of the separator 70 is not particularly limited as long as the effects of the technology disclosed herein are exhibited. Here, the distance (%) between the groove portions 72 means a value expressed as the ratio of the distance T between the groove portions 72 to the length Q in the direction LD orthogonal to the winding axis direction WD of the electrode body 20 (that is, (T / Q)×100 (%)) (see FIGS. 3 and 5). The lower limit of the distance between the groove portions 72 is, from the viewpoint of suitably ensuring the strength of the separator 70, for example, 1% or more, preferably 2% or more, more preferably 5% or more. Also, the lower limit of the distance between the groove portions 72 is, from the viewpoint of improving the impregnation property of the electrolytic solution with respect to the electrode body 20, for example, 30% or less, preferably 20% or less, more preferably 15% or less, and particularly preferably 10% or less. However, it is not limited thereto.

[0032] Examples of the separator 70 include a porous sheet (film) made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Such a porous sheet may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). A heat-resistant layer (HRL) may be provided on the surface of the separator 70.

[0033] The thickness of the separator 70 is not particularly limited, but is, for example, 5 μm to 50 μm, preferably 10 μm to 30 μm.

[0034] The electrolyte (here, a non-aqueous electrolyte) typically contains a non-aqueous solvent and a supporting salt (electrolyte salt). As the non-aqueous solvent, various organic solvents such as carbonates, ethers, esters, nitriles, sulfones, lactones, etc., which are used in the electrolytes of common lithium-ion secondary batteries, can be used without particular limitation. Among them, carbonates are preferred, and specific examples thereof include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC), monofluoromethyl difluoromethyl carbonate (F-DMC), trifluorodimethyl carbonate (TFDMC), etc. Such non-aqueous solvents can be used alone or in appropriate combinations of two or more.

[0035] As the supporting salt, for example, lithium salts such as LiPF6, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI) (preferably LiPF6) can be preferably used. The concentration of the supporting salt is preferably 0.7 mol / L or more and 1.3 mol / L or less.

[0036] In addition, as long as the effects of the present invention are not significantly impaired, the above non-aqueous electrolyte may contain components other than the above-described components, for example, film-forming agents such as oxalato complexes; gas generators such as biphenyl (BP) and cyclohexylbenzene (CHB); thickeners; and various other additives.

[0037] From the above, here, a battery 100 is disclosed which includes an electrode body 20 in which a positive electrode 50 and a negative electrode 60 are laminated via a separator 70, a battery case 30 that houses the electrode body 20, and an electrolyte. Since such a battery 100 includes a separator 70 having the above-described configuration, the impregnation property of the electrolyte is preferably improved.

[0038] Also, as an example above, a battery 100 has been described that includes a wound electrode body (electrode body 20) in which a strip-shaped positive electrode 50 and a strip-shaped negative electrode 60 are laminated via a strip-shaped separator 70 and wound. However, using the separator 70 according to this embodiment, a battery including a laminated electrode body (that is, an electrode body in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated) can be constructed. On the other hand, particularly in a wound electrode body, it is an infiltration mode in which the electrolytic solution infiltrates from two surfaces constituting the positive-negative electrode laminated structure toward the center, and compared with a laminated electrode body in which the electrolytic solution infiltrates from four surfaces constituting the positive-negative electrode laminated structure toward the center, the time required for the infiltration of the electrolytic solution tends to be longer. Therefore, it can be said that a wound electrode body is particularly suitable as an object to which the technology disclosed here is applied. Also, using the separator 70 according to this embodiment, a cylindrical battery, a laminate case type battery, etc. can also be constructed. Furthermore, using the separator 70 according to this embodiment, a non-aqueous electrolyte secondary battery other than a lithium ion secondary battery can be constructed according to a conventionally known method.

[0039] Also, as the capacity of the battery 100 increases, the size of the electrode body 20 becomes larger. Therefore, in the liquid injection process, when infiltrating the electrolytic solution throughout the inside of the electrode body 20, it takes a long time. Also, since the width of the electrodes (positive electrode 50 and negative electrode 60) is wide, the gap between the electrodes and the separator 70 becomes narrow, and there is also a possibility that the infiltration of the electrolytic solution becomes difficult. Therefore, it can be said that a high-capacity battery is suitable as an object to which the technology disclosed here is applied. As an example of such a high-capacity battery, there is a battery 100 including a wound electrode body (electrode body 20) having a height of 5 cm to 10 cm, a width of 10 cm to 25 cm, and a thickness of 1 cm to 5 cm. Here, the height of the electrode body 20 indicates the length in the Z direction in FIG. 3, the width of the electrode body 20 indicates the length in the Y direction in FIG. 3, and the thickness of the electrode body 20 indicates the length in the X direction in FIG. 3. However, it is not intended to be limited to these. Note that WL in FIG. 3 indicates the winding axis.

[0040] <Method for manufacturing a battery> Next, a method for manufacturing the battery 100 will be described. Note that the battery 100 according to the present embodiment is characterized in that a separator 70 having the groove portion 72 as described above is used as a separator, and the steps related to the method for manufacturing the battery can be carried out according to a conventionally known method. As such a separator 70, a purchased product in which the groove portion 72 is formed in advance may be used, or the groove portion 72 may be formed. Examples of the method for forming such a groove portion 72 include a method of bringing a roller having a convex portion corresponding to the groove portion 72 into contact with the separator before the formation of the groove portion 72.

[0041] <Battery applications> The battery 100 can be used for various applications. For example, it can be suitably used as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car or a truck. The type of vehicle is not particularly limited, and examples include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), and a battery electric vehicle (BEV). Since the variation in battery reaction of the battery 100 is reduced, it can be suitably used for constructing a battery pack.

[0042] As described above, one embodiment of the present disclosure has been described, but the above embodiment is merely an example. The present disclosure can be implemented in various other forms. The present disclosure can be implemented based on the content disclosed in this specification and common general knowledge in the art. The technology described in the claims includes various modifications and changes of the above-exemplified embodiments. For example, it is possible to replace a part of the above-described embodiment with another modified form, and it is also possible to add other modified forms to the above-described embodiment. Further, if the technical feature is not described as essential, it can be appropriately deleted.

[0043] For example, in the above embodiment, the groove portion 72 is formed only on one side of the separator 70, but the present invention is not limited thereto. In other embodiments, the groove portion 72 may be formed on both sides of the separator 70. And in such a case, the aspect of the groove portion 72 formed on one side of the separator 70 and the aspect of the groove portion 72 formed on the other side may be the same or different. Also, for example, when the separator has a plurality of groove portions, the configurations of the respective groove portions may be the same or different.

[0044] For example, FIG. 9 is a diagram corresponding to FIG. 5 according to the second embodiment. As shown in FIG. 9, in the second embodiment, the cross-sectional shape of the groove portion 172 is semi-circular. The battery according to the second embodiment may be the same as the above-described battery 100 except that the cross-sectional shape of the groove portion is changed from the groove portion 72.

[0045] For example, FIG. 10 is a diagram corresponding to FIG. 5 according to the third embodiment. As shown in FIG. 10, in the third embodiment, the cross-sectional shape of the groove portion 272 is triangular. The battery according to the third embodiment may be the same as the above-described battery 100 except that the cross-sectional shape of the groove portion is changed from the groove portion 72.

[0046] For example, FIG. 11 is a diagram corresponding to FIG. 5 according to the fourth embodiment. As shown in FIG. 11, in the fourth embodiment, the cross-sectional shape of the groove portion 372 is trapezoidal. The battery according to the fourth embodiment may be the same as the above-described battery 100 except that the cross-sectional shape of the groove portion is changed from the groove portion 72.

[0047] For example, FIG. 12 is a diagram corresponding to FIG. 5 according to the fifth embodiment. As shown in FIG. 12, in the fifth embodiment, the cross-sectional shape of the groove portion 472 is rectangular with a corner having a radius R. The battery according to the fifth embodiment may be the same as the above-described battery 100 except that the cross-sectional shape of the groove portion is changed from the groove portion 72.

[0048] For example, FIG. 13 is a corresponding view of FIG. 5 according to the sixth embodiment. As shown in FIG. 13, in the sixth embodiment, the cross-sectional shape of the groove portion 572 is a pentagonal shape. The battery according to the sixth embodiment may be the same as the above-described battery 100 except that the cross-sectional shape of the groove portion is changed from the groove portion 72.

[0049] For example, FIG. 14 is a corresponding view of FIG. 4 according to the seventh embodiment. As shown in FIG. 14, in the seventh embodiment, the shape of the groove portion 672 in plan view is a trumpet shape. In other words, the opening width V at at least one end (here, both ends) of the ends (70A and 70B) of the separator 70 in the groove portion 672 is larger than the opening width V' in the central region of the groove portion 672. According to such a configuration, the impregnation property of the electrolytic solution from the surface constituting the positive and negative electrode laminate structure A can be more suitably improved. The battery according to the seventh embodiment may be the same as the above-described battery 100 except that the shape of the groove portion in plan view is changed from the groove portion 72.

[0050] For example, FIG. 15 is a corresponding view of FIG. 4 according to the eighth embodiment. As shown in FIG. 15, in the eighth embodiment, the shape of the groove portion 772 in plan view is a slanted line shape. The battery according to the eighth embodiment may be the same as the above-described battery 100 except that the cross-sectional shape of the groove portion is changed from the groove portion 72.

[0051] For example, FIG. 16 is a corresponding view of FIG. 4 according to the ninth embodiment. As shown in FIG. 16, in the ninth embodiment, the shape of the groove portion 872 in plan view is an alternating shape. The battery according to the ninth embodiment may be the same as the above-described battery 100 except that the cross-sectional shape of the groove portion is changed from the groove portion 72.

[0052] For example, FIG. 17 is a corresponding view of FIG. 4 according to the tenth embodiment. As shown in FIG. 17, in the tenth embodiment, the shape of the groove portion 972 in plan view is a wavy line shape. The battery according to the tenth embodiment may be the same as the above-described battery 100 except that the cross-sectional shape of the groove portion is changed from the groove portion 72.

[0053] As described above, specific aspects of the technology disclosed herein include those described in the following items. Item 1: A separator used in a power storage device including an electrode body having a positive-negative electrode laminate structure in which a positive electrode and a negative electrode are laminated via a separator, a case that houses the electrode body, and an electrolyte, the separator having one or more groove portions extending along a direction from one end of the separator constituting one positive-negative electrode laminate structure toward the other end. Item 2: The separator according to Item 1, wherein the groove portion is formed from the one end of the separator to the other end. Item 3: The separator according to Item 2, wherein an opening width at at least one end of the groove portion is larger than an opening width in a central region of the groove portion. Item 4: A power storage device including an electrode body in which a positive electrode and a negative electrode are laminated via a separator, a case that houses the electrode body, and an electrolyte, wherein the separator is the separator according to any one of Items 1 to 3. Item 5: The power storage device according to Item 4, wherein the electrode body is a wound electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are laminated via a strip-shaped separator and wound.

[0054] Hereinafter, embodiments of the present invention will be described, but the present invention is not intended to be limited to those shown in such test examples.

[0055] [Test Example 1] In the following test examples, for eight types of samples in which the depth (%) of the groove portion in the separator was changed as described above, the impregnation property of the electrolyte in the electrode was evaluated.

[0056] <Preparation of Samples> (Preparation of Separator) As a separator, a microporous polyethylene sheet having a single-layer structure of PE was prepared, with a length of 2100 mm (length in the Z direction in Fig. 4), a width of 150 mm (length in the Y direction in Fig. 4), and a thickness of 20 μm. And, as shown in Figs. 4 and 5, separators with six rectangular groove portions formed therein, with the depths (%) of the groove portions as described above being 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, and 0.007 were each prepared. Also, as a comparative object, one with a depth (%) of such groove portions being 0 was fabricated. Note that the width (%) of the groove portions was fixed at 0.0075% and the distance (%) between the groove portions was fixed at 10%. Such groove portions were created using a roll with corresponding portions as convex portions.

[0057] (Fabrication of negative electrode plate) Graphite as a negative electrode active material, styrene-butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener were mixed so that the weight ratio of negative electrode active material:binder:thickener = 100:1:1, and an appropriate amount of ion-exchanged water was added as a solvent to prepare a slurry for forming a negative electrode active material layer. This slurry for forming a negative electrode active material layer was applied onto a negative electrode current collector so that the basis weight was 7 mg / cm 2 . Thereafter, drying and roll pressing were performed to obtain a negative electrode plate.

[0058] (Fabrication of positive electrode plate) Lithium nickel cobalt manganese composite oxide (LiNiCoMnO2) as a positive electrode active material, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were mixed so that the positive electrode active material:conductive material:binder = 100:1:1, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added as a solvent to prepare a slurry for forming a positive electrode active material layer. This slurry for forming a positive electrode active material layer was applied onto a positive electrode current collector made of aluminum foil so that the basis weight was 10 mg / cm 2 . Thereafter, drying and roll pressing were performed to obtain a positive electrode plate.

[0059] Next, a wound electrode body was obtained by laminating a positive electrode plate and a negative electrode plate with a separator interposed therebetween and pressing them into a flat shape. As the two separators, those prepared above were both used. Here, the size of the wound electrode body was 7 cm in height, 15 cm in width, and 1 cm in thickness. Then, after welding a current collector plate to the wound electrode body, the wound electrode body was housed in a square battery case, and a non-aqueous electrolyte was poured. As the non-aqueous electrolyte, LiPF6 was dissolved as a supporting salt in a mixed solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of EC:EMC:DMC = 1:1:1 at a concentration of 1.0 mol / L. Thereafter, by sealing the battery case, a lithium-ion secondary battery for evaluation according to each example was obtained.

[0060] <Evaluation of the impregnation property of the electrolyte in the electrode> After taking out the wound electrode body from the battery case, the wound electrode body was disassembled. The impregnation property of the electrolyte was evaluated by calculating the ratio of the area of the portion wetted with the electrolyte visually confirmed when the total surface area of one side of the positive electrode and the negative electrode was taken as 100%. The results are shown in the graph of Fig. 6.

[0061] As shown in Fig. 6, it was found that in the sample in which the groove portion was formed in the separator, the impregnation property of the electrolyte in the electrode was preferably improved as compared with the sample in which the groove portion was not formed in the separator (i.e., the comparative sample). Also, as shown in Fig. 6, the depth (%) of such a groove portion is preferably 0.001% or more, more preferably 0.002% or more, and particularly preferably 0.003% or more.

[0062] [Test Example 2] In the following test examples, the impregnation property of the electrolyte in the electrode was evaluated for nine types of samples in which the width (%) of the groove portion in the separator was changed as described above.

[0063] <Preparation of samples> (Preparation of separator) As the separator, a separator having the same configuration as that in Test Example 1 was prepared. And, as shown in FIGS. 4 and 5, a separator in which six rectangular groove portions were formed, and the widths (%) of the groove portions as described above were set to 0.0025, 0.005, 0.0075, 0.01, 0.0125, 0.015, 0.0175, and 0.02 were prepared respectively. Further, as a comparison target, one having a groove width (%) of 0 was also produced. Note that the depth (%) of the groove portion was fixed at 0.003% and the distance (%) between the groove portions was fixed at 10%. Such groove portions were formed using a roll having corresponding portions as convex portions.

[0064] Then, except for changing the configuration of the separator, a wound electrode body was obtained in the same manner as the method for producing the sample according to Test Example 1.

[0065] <Evaluation of Electrolyte Impregnation Property> In the same manner as in Test Example 1, the evaluation of the electrolyte impregnation property was performed. The results are shown in the graph of FIG. 7.

[0066] As shown in FIG. 7, it was found that in the sample in which the groove portion was formed in the separator, the impregnation property of the electrolyte in the electrode was preferably improved as compared with the sample in which the groove portion was not formed in the separator (that is, the comparison target sample). Also, as shown in FIG. 7, the depth (%) of such groove portions is preferably 0.0025% or more, more preferably 0.005% or more, and particularly preferably 0.0075% or more.

[0067] [Test Example 3] In the following test example, the impregnation property of the electrolyte in the electrode was evaluated for five types of samples in which the distance (%) between the groove portions as described above in the separator was changed.

[0068] <Production of Sample> (Production of Separator) As a separator, a separator having the same configuration as in Test Example 1 was prepared. Then, as shown in FIGS. 4 and 5, separators having six rectangular groove portions formed therein, with the distances (%) between the groove portions as described above being 5, 10, 15, and 20, were prepared respectively. Also, as a comparative object, one having a distance (%) between such groove portions of 0 was fabricated. Note that the depth (%) of the groove portion was fixed at 0.003% and the width (%) of the groove portion was fixed at 0.0075%. Such groove portions were formed using a roll with corresponding portions as convex portions.

[0069] Then, except for changing the configuration of the separator, a wound electrode body was obtained in the same manner as the method for preparing the sample according to Test Example 1.

[0070] <Evaluation of electrolyte impregnation> In the same manner as in Test Example 1, the evaluation of the electrolyte impregnation was performed. The results are shown in the graph of FIG. 8.

[0071] As shown in FIG. 8, it was found that in the sample in which groove portions were formed in the separator, the impregnation of the electrolyte in the electrode was preferably improved as compared with the sample in which no groove portions were formed in the separator (i.e., the comparative object sample). Also, as shown in FIG. 8, the depth (%) of such groove portions is preferably 20% or less, more preferably 15% or less, and particularly preferably 10% or less. Further, from the results of Test Examples 1 to 3, for example, when the depth (%) of the groove portion of the separator is 0.003% or more, the width (%) of the groove portion is 0.0075% or more, and the distance (%) between the groove portions is 10% or less, it was confirmed that it is particularly preferable from the viewpoint of the impregnation of the electrolyte.

Explanation of reference numerals

[0072] 20 Electrode body 30 Battery case 36 Safety valve 42 Positive electrode terminal 42a Positive electrode current collector 44 Negative electrode terminal 44a Negative electrode current collector 50 Positive electrode 52 Positive electrode current collector Non-formed part of the positive electrode active material layer 54 Positive electrode active material layer 60 Negative electrode 62 Negative electrode current collector 62a Non-formed part of the negative electrode active material layer 64 Negative electrode active material layer 70, 170, 270, 370, 470, 570, 670, 770, 870, 970 Separator 72, 172, 272, 372, 472, 572, 672, 772, 872, 972 Groove part 100 Battery

Claims

1. An electrode body having a positive-negative electrode laminate structure in which a positive electrode and a negative electrode are laminated via a separator, a case for housing the electrode body, an electrolytic solution, A separator used in a power storage device comprising: On the surface of the separator, there are one or more groove portions formed along the direction from one end of the separator constituting one of the positive-negative electrode laminate structures toward the other end and reaching the other end. A separator in which the opening widths of both ends in the groove portion are larger than the opening width of the central region along the direction from the ends.

2. A power storage device comprising a positive electrode and a negative electrode, an electrode body laminated via a separator, a case for housing the electrode body, an electrolytic solution, wherein the separator is the separator according to Claim 1.

3. The power storage device according to Claim 2, wherein the electrode body is a wound electrode body in which a strip-shaped positive electrode and a strip-shaped negative electrode are laminated and wound via a strip-shaped separator. ​

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