Energy storage devices

Abstract

This invention provides a technology to improve the current collection efficiency of the first electrode of an energy storage device. [Solution] The energy storage device disclosed herein comprises a first electrode (22) having a first current collector (22a) and a first active material layer (22b) provided on the first current collector (22a), a second electrode (24), a separator (23), and a conductive layer (27). The conductive layer (27) is provided between the first active material layer (22b) and the separator (23), extending from the surface of the first active material layer (22b) to the first current collector (22a).

Description

[Technical Field]

[0001] This disclosure relates to an energy storage device. [Background technology]

[0002] Examples of energy storage devices include rechargeable batteries such as lithium-ion batteries. In recent years, these types of rechargeable batteries have been suitably used as portable power sources for personal computers and mobile devices, as well as as power sources for vehicle propulsion systems such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs).

[0003] In the positive electrode for a non-aqueous electrolyte secondary battery disclosed in Japanese Patent Publication No. 2018-055836, a positive electrode active material layer containing positive electrode active material is formed on the surface of the current collector. The thickness of the positive electrode active material layer is 150 to 1500 μm. At least a portion of the surface of the positive electrode active material is coated with a coating agent containing a coating resin and a conductive additive. The porosity of the positive electrode active material layer is 35.0 to 50.0%, and its density is 2.1 to 3.0 g / cm³. 3 The publication states that in a non-aqueous electrolyte secondary battery having a positive electrode active material layer with such a configuration, it is possible to improve the output characteristics at high rates.

[0004] Japanese Patent Publication No. 2023-027096 discloses a microporous film or substrate comprising a layer of polycrystalline metal and / or metal oxide on at least one side of a polymer porous film. The layer is deposited by a deposition method. The publication states that the modified film may have improved impedance / charge transfer, dielectric breakdown, and / or improved safety.

[0005] Japanese Patent Publication No. 2012-043629 discloses a separator for use in a non-aqueous electrolyte secondary battery. The separator has a conductive layer. The apparent volume resistivity of the conductive layer is 1 × 10⁻⁶ -4 Ω cm to 1×10 6The coefficient of force is Ω·cm. The meltdown temperature of the separator is 170°C or higher. The publication states that this configuration can enhance the safety of non-aqueous electrolyte secondary batteries.

[0006] The battery separator disclosed in Japanese Patent Publication No. 2008-084866 includes a separator and a conductive layer placed on the separator, wherein the conductive layer is applied so as to be in contact with the electrodes, thereby providing a new route for current to and from the electrodes. The publication states that such a configuration can improve the cycle life of the battery.

[0007] In the lithium-ion secondary battery disclosed in Japanese Patent Publication No. 2011-222215, the separator has a resin layer and a porous metal layer applied to one side thereof, and the metal layer is arranged to face the negative electrode. The publication states that with this configuration, the amount of metallic lithium deposited by high-rate charging is reduced, and excellent high-rate charge-discharge characteristics can be achieved. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2018-055836 [Patent Document 2] Japanese Patent Publication No. 2023-027096 [Patent Document 3] Japanese Patent Publication No. 2012-043629 [Patent Document 4] Japanese Patent Publication No. 2008-084866 [Patent Document 5] Japanese Patent Publication No. 2011-222215 [Overview of the project] [Problems that the invention aims to solve]

[0009] The inventors of this invention want to improve the current collection efficiency at the electrodes.

Means for Solving the Problem

[0010] The power storage device disclosed herein includes a first electrode having a first current collector and a first active material layer provided on the first current collector, a second electrode, a separator, and a conductive layer. The conductive layer is provided between the first active material layer and the separator, extending from the surface of the first active material layer to the first current collector. With such a configuration, the current collection efficiency in the first electrode can be enhanced.

Brief Description of the Drawings

[0011] [Figure 1] FIG. 1 is a schematic perspective view of the power storage device 100. [Figure 2] FIG. 2 is a sectional view taken along line II-II of FIG. 1. [Figure 3] FIG. 3 is a schematic view of the electrode body 20. [Figure 4] FIG. 4 is a partial sectional view of the electrode body 20. [Figure 5] FIG. 5 is a partial sectional view of the electrode body 220.

Modes for Carrying Out the Invention

[0012] Hereinafter, an embodiment of the power storage device disclosed herein will be described. The embodiment described here does not particularly limit the technology disclosed here. The technology disclosed here is not limited to the embodiment described here unless otherwise specified. The drawings are schematically drawn and do not necessarily reflect the actual objects. Also, members and parts having the same function may be appropriately assigned the same reference numerals, and redundant descriptions may be omitted. Also, the notation "A~B" indicating a numerical range means "A or more and B or less" and also includes the meaning of "exceeding A and being less than B" unless otherwise specified.

[0013] In this specification, the "power storage device" refers to a device in which charge carriers move between a pair of electrodes (a positive electrode and a negative electrode) through an electrolyte to cause charge and discharge. The power storage device includes secondary batteries such as lithium-ion secondary batteries; capacitors such as lithium-ion capacitors and electric double-layer capacitors. Hereinafter, embodiments in the case where the power storage device is a lithium-ion secondary battery will be described.

[0014] <First Embodiment> FIG. 1 is a schematic perspective view of a power storage device 100. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. As shown in FIGS. 1 and 2, the power storage device 100 includes a case 10, an electrode body 20, a positive electrode terminal 30, a negative electrode terminal 40, a positive electrode current collector member 50, a negative electrode current collector member 60, various insulating members, and a non-aqueous electrolyte (not shown).

[0015] The case 10 is an outer container that houses the electrode body 20 and the non-aqueous electrolyte. Here, the case 10 is a flat rectangular case. The material constituting the case 10 is not particularly limited, and for example, a material constituting a case of this type of power storage device may be appropriately used.

[0016] As shown in FIGS. 1 and 2, the case 10 includes a main body 12 and a sealing plate 14. The main body 12 has a bottom surface 12a, a pair of opposing first side surfaces 12b, and a pair of opposing second side surfaces 12c. The bottom surface 12a is rectangular. As shown in FIG. 2, the opposing portion with the bottom surface 12a is an opening 12h. The pair of opposing first side surfaces 12b are rectangular and extend from a pair of opposing long sides of the bottom surface 12a. The pair of opposing second side surfaces 12c are rectangular and extend from a pair of opposing short sides of the bottom surface 12a. In this embodiment, the area of the pair of opposing first side surfaces 12b is larger than the area of the pair of opposing second side surfaces 12c.

[0017] As shown in Figures 1 and 2, the sealing plate 14 is a rectangular flat plate and has a shape corresponding to the opening 12h. The sealing plate 14 has an injection hole 15, a safety valve 17, a first terminal mounting hole 18, and a second terminal mounting hole 19. The injection hole 15 is the part into which the non-aqueous electrolyte is injected into the case 10. As shown in Figures 1 and 2, the injection hole 15 is sealed by a sealing member 16. The safety valve 17 is a thin-walled portion that is set to release the internal pressure when the internal pressure of the case 10 rises above a predetermined level, for example. The first terminal mounting hole 18 is a through hole into which the positive electrode terminal 30 is attached. The second terminal mounting hole 19 is a through hole into which the negative electrode terminal 40 is attached. The sealing plate 14 closes the opening 12h and is welded (e.g., laser welded) to the main body 12.

[0018] The electrode body 20 is a power generation element of the energy storage device 100. Figure 3 is a schematic diagram of the electrode body 20. Figure 4 is a partial cross-sectional view of the electrode body 20. Figure 4 schematically shows the laminated structure of the electrodes near the positive electrode tab 22t in the electrode body 20. As shown in Figures 3 and 4, the electrode body 20 is a laminated electrode body comprising a sheet-shaped positive electrode 22, a sheet-shaped negative electrode 24, and a sheet-shaped separator 23. In the electrode body 20, the positive electrode 22 and the negative electrode 24 are superimposed with the separator 23 in between. The number of positive electrodes 22, the number of negative electrodes 24, and the number of separators 23 in the electrode body 20 can be appropriately set according to the desired capacity of the energy storage device 100. The positive electrode 22 is an example of a first electrode in the energy storage device disclosed herein. The negative electrode 24 is an example of a second electrode in the energy storage device disclosed herein.

[0019] As shown in Figures 3 and 4, the positive electrode 22 comprises a sheet-like positive electrode current collector 22a and a positive electrode active material layer 22b. The positive electrode current collector 22a comprises a rectangular sheet-like body portion 22a1 and a positive electrode tab 22t. In this embodiment, the positive electrode active material layer 22b is provided on the body portion 22a1 of the positive electrode current collector 22a. The positive electrode active material layer 22b is provided on the surface (here, both sides) of the body portion 22a1 of the positive electrode current collector 22a. As shown in Figure 3, the positive electrode tab 22t protrudes outward from one of a pair of opposing short sides of the body portion 22a1. The positive electrode tab 22t is an exposed portion of the positive electrode current collector 22a where the positive electrode active material layer 22b is not provided. The positive electrode current collector 22a is, for example, aluminum foil.

[0020] The positive electrode active material layer 22b contains, for example, a positive electrode active material. The positive electrode active material is not particularly limited as long as the effects of the technology disclosed herein are realized, and any positive electrode active material having a conventionally known composition used in this type of application may be used. The positive electrode active material may be, for example, a lithium composite oxide or a lithium transition metal phosphate compound. The crystal structure of the positive electrode active material is not particularly limited and may be a layered structure, a spinel structure, an olivine structure, etc.

[0021] As lithium composite oxides, lithium transition metal composite oxides containing at least one of Ni, Co, and Mn as a transition metal element are preferred. Examples of lithium transition metal composite oxides include lithium nickel-based composite oxides, lithium cobalt-based composite oxides, lithium manganese-based composite oxides, lithium nickel-manganese-based composite oxides, lithium nickel-cobalt-manganese-based composite oxides, lithium nickel-cobalt-aluminum-based composite oxides, and lithium iron-nickel-manganese-based composite oxides. These positive electrode active materials may be used individually or in combination of two or more.

[0022] In this specification, the term "lithium nickel cobalt manganese composite oxide" includes, in addition to oxides composed of Li, Ni, Co, Mn, and O as constituent elements, oxides containing one or more additional elements other than these. Examples of the additional elements include transition metal elements such as Mg, Ca, Al, Ti, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, W, Na, Fe, Zn, Sn, and typical metal elements. The additional elements may also be metalloid elements such as B, C, Si, P; and non-metal elements such as S, F, Cl, Br, I. This also applies to the above-mentioned lithium nickel-based composite oxides, lithium cobalt-based composite oxides, lithium manganese-based composite oxides, lithium nickel manganese-based composite oxides, lithium nickel cobalt aluminum-based composite oxides, lithium iron nickel manganese-based composite oxides, etc.

[0023] Examples of lithium transition metal phosphate compounds include lithium iron phosphate (LiFePO4), lithium manganese phosphate (LiMnPO4), lithium manganese iron phosphate, etc. Examples of the positive electrode active material include, for example, LiNi 0.33 Co 0.33 Mn 0.33 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNiO2, LiCoO2, LiFeO2, LiMn2O4, LiNi 0.5 Mn 1.5 O4, etc. can be preferably used.

[0024] The positive electrode active material layer 22b may contain conductive materials, binders, etc., in addition to the positive electrode active material. Examples of conductive materials include carbon black such as acetylene black (AB) and other carbon materials such as graphite. Examples of binders include polyvinylidene fluoride (PVdF). The content of the positive electrode active material in the total positive electrode active material layer 22b is preferably 70% by mass or more, more preferably 80% to 98% by mass, and even more preferably 85% to 95% by mass. The content of the conductive material in the total positive electrode active material layer 22b is, for example, 0.1% to 20% by mass. The content of the binder in the total positive electrode active material layer 22b is, for example, 0.5% to 15% by mass.

[0025] As shown in Figures 3 and 4, the negative electrode 24 comprises a sheet-like negative electrode current collector 24a and a negative electrode active material layer 24b. The negative electrode current collector 24a comprises a rectangular sheet-like body portion 24a1 and a negative electrode tab 24t. In this embodiment, the negative electrode active material layer 24b is provided on the body portion 24a1 of the negative electrode current collector 24a. The negative electrode active material layer 24b is provided on the surface (here, both sides) of the body portion 24a1 of the negative electrode current collector 24a. In this embodiment, the negative electrode tab 24t protrudes outward from one of a pair of opposing short sides of the body portion 24a1. The negative electrode tab 24t is an exposed portion of the negative electrode current collector 24a where the negative electrode active material layer 24b is not provided. The negative electrode current collector 24a is, for example, copper foil.

[0026] The negative electrode active material layer 24b contains, for example, a negative electrode active material. Examples of negative electrode active materials include carbon materials such as natural graphite and artificial graphite; silicon; and the like. In addition to the negative electrode active material, the negative electrode active material layer 24b may also contain, for example, a binder, a thickener, and the like. Examples of binders include styrene-butadiene rubber (SBR). Examples of thickeners include carboxymethylcellulose (CMC). The content of the negative electrode active material relative to the entire negative electrode active material layer 24b is, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 90% to 99% by mass, and may be 95% to 99% by mass. The content of the binder relative to the entire negative electrode active material layer 24b is, for example, 0.5% to 10% by mass.

[0027] In this embodiment, the separator 23 separates the positive electrode 22 and the negative electrode 24. In this embodiment, the separator 23 is a rectangular sheet that covers the positive electrode active material layer 22b and a portion of the positive electrode tab 22t. As shown in Figure 4, the separator 23 covers the end face 22b1 in the thickness direction of the positive electrode active material layer 22b. In the configuration shown in Figure 4, the separator 23 is joined to the positive electrode tab 22t (joint W). For example, ultrasonic welding can be preferably used as such a joining method.

[0028] While not particularly limited, the thickness of the separator 23 is preferably 5 μm to 50 μm, and more preferably 10 μm to 30 μm, from the viewpoint of facilitating contact between the conductive layer 27 and the side surface 22b2 in the thickness direction of the positive electrode active material layer 22b, in addition to the end face 22b1 of the positive electrode active material layer 22b, and from the viewpoint of improving the permeability of the electrolyte in the separator 23 provided with the conductive layer 27. From a similar viewpoint, the air permeability of the separator 23 obtained by the Gurley test method is not particularly limited, but is preferably 350 seconds / 100 cc or less.

[0029] As the separator 23, for example, a porous sheet (film) made of a resin material such as polyethylene (PE), polypropylene (PP), polyester, cellulose, or polyamide can be used. The porous sheet used as the separator 23 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).

[0030] As shown in Figure 4, the conductive layer 27 is provided between the positive electrode active material layer 22b and the separator 23, extending from the surface of the positive electrode active material layer 22b to the positive electrode current collector 22a. Here, "provided from the surface of the positive electrode active material layer 22b to the positive electrode current collector 22a" means that both the surface of the positive electrode active material layer 22b and the surface of the positive electrode current collector 22a have the conductive layer 27 and are connected by the conductive layer 27. In this embodiment, the conductive layer 27 is provided on the surface of the separator 23. In the configuration shown in Figure 4, the conductive layer 27 is provided on the first surface 23a of the separator 23. The first surface 23a is the surface located on the positive electrode 22 side. In this embodiment, the conductive layer 27 is not provided on the second surface 23b of the separator 23. The second surface 23b is the surface opposite to the first surface 23a and is located on the negative electrode 24 side. In this embodiment, the conductive layer 27 covers the positive electrode active material layer 22b and also covers a portion of the positive electrode tab 22t. The conductive layer 27 is bonded to the positive electrode current collector 22a (in this case, the positive electrode tab 22t) at the junction W between the positive electrode current collector 22a and the separator 23.

[0031] In this embodiment, the conductive layer 27 is a metal layer. The conductive layer 27 may consist of, for example, aluminum, titanium, stainless steel, nickel, or an alloy thereof, or any of these metals. The conductive layer 27 can be formed, for example, by vapor deposition, sputtering, plating, etc., on the separator 23. Among the methods for forming the conductive layer 27, physical vapor deposition such as vacuum deposition and electroless plating are preferably used. The thickness of the conductive layer 27 is not particularly limited, and may be set to, for example, 10 nm to 1000 nm, preferably 100 nm to 900 nm.

[0032] The positive electrode terminal 30 is a component electrically connected to the positive electrode 22 of the electrode body 20. As shown in Figures 1 and 2, the positive electrode terminal 30 is mounted on the sealing plate 14. As shown in Figure 2, the positive electrode terminal 30 is mounted on the right side of the sealing plate 14 and connected to the positive electrode tab 22t via the positive electrode current collector 50. The positive electrode terminal 30 comprises a positive electrode external terminal 31 and a positive electrode internal terminal 32. As shown in Figures 1 and 2, the positive electrode external terminal 31 is plate-shaped and positioned along the outer surface of the sealing plate 14. As shown in Figure 2, the positive electrode internal terminal 32 has a base portion 32a and a shaft portion 32b. The base portion 32a is plate-shaped and positioned along the outer surface of the sealing plate 14. The shaft portion 32b is cylindrical, extends vertically from the base portion 32a, and passes through the through hole 31h of the positive electrode external terminal 31 and the first terminal mounting hole 18 of the sealing plate 14. The lower end of the shaft portion 32b is further connected to the positive electrode current collector member 50. The positive electrode terminal 30 may be made of aluminum, for example.

[0033] The negative electrode terminal 40 is a component electrically connected to the negative electrode 24 of the electrode body 20. As shown in Figures 1 and 2, the negative electrode terminal 40 is attached to the sealing plate 14. As shown in Figure 2, the negative electrode terminal 40 is attached to the left side of the sealing plate 14 and is connected to the negative electrode tab 24t via the negative electrode current collector 60. The negative electrode terminal 40 may be made of copper, for example. Other than this, the negative electrode terminal 40 may have the same shape as the positive electrode terminal 30. In Figures 1 and 2, the reference numerals "41" and "42" indicate the "negative electrode external terminal" and the "negative electrode internal terminal," respectively.

[0034] The positive electrode current collector 50 is a component electrically connected to the positive electrode 22 of the electrode body 20. As shown in Figure 2, the positive electrode current collector 50 is attached to the sealing plate 14 and connected to the positive electrode terminal 30 and the positive electrode tab 22t. The positive electrode current collector 50 has a terminal connection portion 51 and a tab connection portion 52. The terminal connection portion 51 has an L-shaped cross-section and has a portion located on the inner surface of the sealing plate 14 and a portion extending in the vertical direction. The portion located on the inner surface of the sealing plate 14 is connected to the shaft portion 32b of the positive electrode internal terminal 32. The portion extending in the vertical direction is connected to the tab connection portion 52. The tab connection portion 52 is plate-shaped and extends in the vertical direction. The tab connection portion 52 is connected to the positive electrode tab 22t. The positive electrode current collector 50 may be made of aluminum, for example.

[0035] The negative electrode current collector 60 is a component electrically connected to the negative electrode 24 of the electrode body 20. As shown in Figure 2, the negative electrode current collector 60 is attached to the sealing plate 14 and connected to the negative electrode terminal 40 and the negative electrode tab 24t. The negative electrode current collector 60 may be made of copper, for example. Other than this, the negative electrode current collector 60 may have the same shape as the positive electrode current collector 50. In Figure 2, the reference numerals "61" and "62" indicate the "terminal connection part" and the "tab connection part," respectively.

[0036] As shown in Figure 2, the insulating members of the energy storage device 100 include a first insulating member 71, a second insulating member 72, and an insulating film (not shown). The first insulating member 71 is positioned between the positive electrode terminal 30 and the sealing plate 14, and between the negative electrode terminal 40 and the sealing plate 14. The second insulating member 72 is positioned between the positive electrode current collector 50 and the sealing plate 14, and between the negative electrode current collector 60 and the sealing plate 14. The insulating film (not shown) is a resin film that encloses the electrode body 20 and insulates the electrode body 20 from the case 10 and other metal members. Any insulating material (e.g., resin material) conventionally used in this type of energy storage device can be used as the material for the various insulating members without particular limitation.

[0037] A non-aqueous electrolyte includes, for example, a non-aqueous solvent and a supporting salt. Examples of non-aqueous solvents include organic solvents such as various carbonates, ethers, esters, nitriles, sulfones, and lactones used in this type of application. Among these, carbonates are preferably used. Examples of carbonates include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC) (preferably monofluoroethylene carbonate), monofluoromethyldifluoromethyl carbonate (F-DMC), and trifluorodimethyl carbonate (TFDMC). A single non-aqueous solvent may be used alone, or two or more non-aqueous solvents may be used in combination. Examples of supporting salts include lithium salts such as LiPF6, LiBF4, and LiClO4. The concentration of the supporting salt is preferably, for example, 0.7 mol / L to 1.4 mol / L. The non-aqueous electrolyte may contain additives used for this type of application as needed. Examples of additives may include film-forming agents such as LiB(C2O4)2 (LiBOB) and LiBF2 (C2O4); gas-generating agents such as biphenyl (BP) and cyclohexylbenzene (CHB); thickeners; and so on.

[0038] The energy storage device 100 can be used for various applications. Suitable applications include power supplies for vehicles such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). The energy storage device 100 can be used, for example, as a battery in a small-scale power storage device. The energy storage device 100 can also be used, for example, in the form of a battery pack in which multiple devices are connected in series and / or parallel.

[0039] As described above, the energy storage device 100 includes a positive electrode 22, a negative electrode 24, a separator 23 separating the positive electrode 22 and the negative electrode 24, and a conductive layer 27. The positive electrode 22 includes a positive electrode current collector 22a and a positive electrode active material layer 22b provided on the positive electrode current collector 22a. The conductive layer 27 is provided between the positive electrode active material layer 22b and the separator 23, extending from the surface of the positive electrode active material layer 22b to the positive electrode current collector 22a.

[0040] The energy storage device 100 includes a conductive layer 27 between the positive electrode active material layer 22b and the separator 23, extending from the surface of the positive electrode active material layer 22b to the positive electrode current collector 22a. This allows current collection from the positive electrode active material layer 22b to be possible through both the positive electrode current collector 22a and the conductive layer 27. As a result, the current collection distance from the positive electrode active material layer 22b to the positive electrode 22 can be shortened, and consequently, the current collection efficiency can be increased.

[0041] The effects described above are desirable, for example, from the viewpoint of increasing the energy density of the energy storage device 100. To increase the energy density of the energy storage device 100, for example, the positive electrode active material layer 22b can be made thicker. Although not particularly limited, the thickness of the positive electrode active material layer 22b can be set to approximately 10 μm to 300 μm. When the positive electrode active material layer 22b is made thicker from the viewpoint of increasing energy density, the thickness of the positive electrode active material layer 22b is preferably 50 μm to 300 μm, and more preferably 100 μm to 300 μm.

[0042] The positive electrode current collector 22a may comprise a rectangular sheet-shaped main body 22a1 and a positive electrode tab 22t projecting outward from a first side (in this case, the short side) of the main body 22a1. The conductive layer 27 may be provided on the first side, extending from the surface of the positive electrode active material layer 22b to the positive electrode tab 22t. The positive electrode tab 22t is, for example, a portion electrically connected to another component (in this case, the positive electrode current collector 50). By providing the conductive layer 27 extending from the surface of the positive electrode active material layer 22b to the positive electrode tab 22t, in addition to the effects described above, connectivity from the positive electrode 22 to other components can be improved. In the above configuration, the electrode body 20 containing the positive electrode 22 may be a laminated electrode body. This can increase the productivity of the energy storage device 100.

[0043] A conductive layer 27 may be provided on the surface of the separator 23. In this embodiment, since only a separator 23 with a conductive layer 27 is provided as the separator, existing manufacturing lines can be used more easily for manufacturing the energy storage device 100. In addition, since the material of the conductive layer 27 is less likely to adhere to the positive electrode active material, the positive electrode active material can be recycled more easily.

[0044] The conductive layer 27 may be bonded to the positive electrode current collector 22a. By integrating the conductive layer 27 and the positive electrode current collector 22a through bonding, the effects of the technology disclosed herein can be better realized.

[0045] The conductive layer 27 may be a metal vapor-deposited layer. This allows for more reliable integration of the separator 23 and the conductive layer 27, thereby better reducing the risk of the conductive layer 27 delaminating from the separator 23 during the manufacturing process. For this reason, such an embodiment is preferred for realizing the effects of the technology disclosed herein.

[0046] The embodiments of the technology disclosed herein have been described above. The embodiments described above are merely examples of how the technology disclosed herein is applied and do not limit the scope of the technology disclosed herein.

[0047] <Second Embodiment> For example, in the first embodiment described above, a separator 23 provided with a conductive layer 27 was used. However, the conductive layer is not limited to being provided on the separator. Figure 5 is a partial cross-sectional view of the electrode body 220. Figure 5 schematically shows the laminated structure of the electrodes near the positive electrode tab 222t in the electrode body 220. The negative electrode is not shown in Figure 5. As shown in Figure 5, the electrode body 220 comprises a positive electrode 222, a negative electrode, and a separator 223 that separates the positive electrode 222 and the negative electrode. The electrode body 220 is a laminated electrode body in this case. The positive electrode 222 comprises a positive electrode current collector 222a and a positive electrode active material layer 222b. The positive electrode current collector 222a may be the same as the positive electrode current collector 22a described above (see Figures 3 and 4). The positive electrode active material layer 222b may be the same as the positive electrode active material layer 22b described above (see Figures 3 and 4). The separator 223 may be the same as the separator 23 described above (see Figures 3 and 4).

[0048] In the embodiment shown in Figure 5, a conductive layer 227 is provided on the surface of the positive electrode active material layer 222b. In this embodiment, the conductive layer 227 is provided on the end face 222b1 in the thickness direction of the positive electrode active material layer 222b, the side surface 222b2 along the same direction, and a part of the surface of the positive electrode current collector 222a (in this case, a part of the surface of the positive electrode tab 222t).

[0049] The conductive layer 227 may be, for example, a metal layer. The conductive layer 227 may include, for example, aluminum, titanium, stainless steel, nickel, or alloys thereof, or consist of any of these metals. The conductive layer 227 can be formed, for example, by performing vapor deposition, sputtering, plating, etc., on a portion of the surface of the positive electrode active material layer 222b and the positive electrode current collector 222a. Among the methods for forming the conductive layer 227, physical vapor deposition such as vacuum deposition and electroless plating are preferably used. The thickness of the conductive layer 227 is not particularly limited, but may be set to, for example, 10 nm to 1000 nm, preferably 100 nm to 900 nm.

[0050] Thus, the conductive layer 227 may be provided on the surface of the positive electrode active material layer 222b. In this embodiment as well, the effects of the technology disclosed herein can be appropriately realized. Furthermore, providing the conductive layer 227 on the surface of the positive electrode active material layer 222b is preferable because it can improve the adhesion between the conductive layer 227 and the positive electrode active material layer 222b.

[0051] The conductive layer 227 may cover at least a portion of the end face 222b1 in the thickness direction of the positive electrode active material layer 222b, and at least a portion of the side surface 222b2 along the same direction. This increases the area in contact between the conductive layer 227 and the positive electrode active material layer 222b. As a result, the effects of the technology disclosed herein can be better realized.

[0052] <Other Embodiments> In the embodiments described above, the conductive layer is provided on the positive electrode side. However, the technology disclosed herein is not limited to this. The conductive layer may be provided on the negative electrode side instead of the positive electrode side, or together with the positive electrode side. When the conductive layer is provided on the negative electrode side, the metal included in or constituting the conductive layer is preferably, for example, copper, nickel, or an alloy thereof. The method for providing the conductive layer on the negative electrode side may be the same as the method for providing the conductive layer on the positive electrode side.

[0053] In the embodiments described above, a laminated electrode body was used. However, the technology disclosed herein is not limited thereto. The energy storage device disclosed herein may, for example, include a wound electrode body. The wound electrode body is an electrode body formed by winding a long sheet-shaped positive electrode and a long sheet-shaped negative electrode in the longitudinal direction of the sheet with a long sheet-shaped separator interposed between them. In the wound electrode body, the conductive layer may be provided between the separator and the positive electrode active material layer and / or the negative electrode active material layer. The conductive layer may be provided on the surface of the separator, or on the positive electrode active material layer and / or the negative electrode active material layer and on the current collector.

[0054] The following describes examples of tests relating to the technologies disclosed herein, but it is not intended that the technologies disclosed herein are limited to those shown in the following examples.

[0055] [Manufacturing of test cells] <Examples> LiNi as a positive electrode active material 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (LNCM), acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were prepared. These were mixed with N-methylpyrrolidone (NMP) in a mass ratio of LNCM:AB:PVdF = 92:5:3 to prepare a positive electrode slurry. The positive electrode slurry was applied to both sides of a rectangular sheet of aluminum foil with a thickness of 15 μm, dried, and then pressed to the desired thickness. This was then processed to the desired dimensions, and positive electrode tabs (aluminum pieces) were attached to obtain a positive electrode sheet.

[0056] Graphite particles were prepared as the negative electrode active material, styrene-butadiene rubber (SBR) as the binder, and carboxymethylcellulose (CMC) as the thickener. These were mixed with deionized water in a mass ratio of graphite particles / SBR / CMC = 99:0.5:0.5 to prepare a negative electrode slurry. The negative electrode slurry was applied to one side of a rectangular sheet of copper foil with a thickness of 10 μm, dried, and then pressed to the desired thickness. This was then processed to the desired dimensions, and negative electrode tabs (copper pieces) were attached to obtain a negative electrode sheet.

[0057] Two porous polyolefin sheets (20 μm thick) with a three-layer structure of PP / PE / PP were prepared as the substrate for the separator. An aluminum vacuum deposition layer (aluminum deposition layer) was formed on one side of each of these two sheets using an ULVAC vacuum deposition apparatus. Next, a positive electrode sheet was sandwiched between the conductive layer-forming surfaces of the two separators. At this time, the tip of the positive electrode tab protruded from the separator. Next, the base end of the separator and the positive electrode tab were joined by ultrasonic welding to obtain a composite of the separator and the positive electrode sheet. Next, a negative electrode sheet was placed on each of the separators of the composite (in this case, on the surface opposite to the conductive layer-forming surface) to obtain an electrode body. In the electrode body obtained here, a positive electrode sheet with positive electrode active material layers on both sides was sandwiched between two negative electrode sheets, each with a negative electrode active material layer on one side, with a conductive layer-coated separator in between.

[0058] The electrode body was inserted into an aluminum laminate sheet enclosure, a non-aqueous electrolyte was injected, and the opening of the enclosure was sealed to prepare the test cell for the example. The composition (volume ratio) of the non-aqueous electrolyte was EC / DMC / EMC = 30:30:40. LiPF6 was dissolved in the non-aqueous electrolyte at a concentration of 1 mol / L as a supporting salt.

[0059] <Comparative Example> A separator substrate without a conductive layer was used as the separator. Aside from this, the test cell for the comparative example was prepared using the same materials and procedures as in the example.

[0060] [Initial capacity measurement] A test cell was subjected to one charge-discharge cycle at a constant current charge rate of 0.05C under 25°C conditions. This cycle involved charging with a constant current charge rate of 0.05C until the voltage between the positive and negative electrodes reached 4.2V, followed by constant current discharge at a constant current charge rate of 0.05C until the voltage between the positive and negative electrodes reached 2.5V. The discharge capacity at this time was measured and defined as the initial capacity.

[0061] [Output IV Resistance Evaluation] A test cell with a state of charge (SOC) of 100% was placed in a constant temperature bath at 25°C. With the SOC adjusted to 50%, it was discharged for 10 seconds at currents of 1C, 1.5C, 2C, and 3C. The cell voltage was measured during discharge at each current value, and the current value and cell voltage were plotted to determine the IV characteristics during discharge. The IV resistance during discharge was calculated from the slope of the resulting straight line. The results are shown in the corresponding column of Table 1. Note that the results shown in Table 1 are relative values, with the calculated values ​​in the comparative example set to 100.

[0062] [Table 1]

[0063] As shown in Table 1, the IV resistance during discharge in the example was lower than that during discharge in the comparative example. The test cell of the example comprises a positive electrode having a positive electrode current collector and a positive electrode active material layer provided on the positive electrode current collector, a negative electrode, a separator separating the positive electrode and the negative electrode, and a conductive layer. The conductive layer is provided between the positive electrode active material layer and the separator, extending from the surface of the positive electrode active material layer to the positive electrode current collector. From the results obtained in the above test example, it was found that the current collection efficiency at the positive electrode is improved with this configuration.

[0064] The technologies disclosed herein may include the technologies described in the following sections. Section 1: A first electrode comprising a first current collector and a first active material layer provided on the first current collector; second electrode; A separator that separates the first electrode and the second electrode; and, A conductive layer is provided between the first active material layer and the separator, extending from the surface of the first active material layer to the first current collector. Equipped with, Energy storage device. Section 2: The first current collector comprises a rectangular sheet-shaped main body and a first tab protruding outward from a first side of the main body. The conductive layer is provided on the first side, extending from the surface of the first active material layer to the first tab. The energy storage device described in item 1. Section 3: The conductive layer is provided on the surface of the separator. A power storage device as described in item 1 or 2. Section 4: The conductive layer is bonded to the first current collector. A power storage device as described in any one of items 1 to 3. Section 5: The conductive layer is provided on the surface of the first active material layer. A power storage device as described in any one of items 1 to 4. Item 6: The conductive layer covers at least a portion of the end face in the thickness direction of the first active material layer and at least a portion of the side surface along the same direction. A power storage device as described in any one of items 1 to 5. Section 7: The conductive layer is a metal vapor-deposited layer. A power storage device as described in any one of items 1 to 6.

[0065] The embodiments of the technology disclosed herein have been described above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples illustrated above. [Explanation of symbols]

[0066] 20 Electrode body 22 Positive electrode 22a Positive electrode current collector 22a1 Main body 22b Positive electrode active material layer 22b1 End face 22b2 side 23 Separator 24 Negative electrode 24a Negative electrode current collector 24b Negative electrode active material layer 24t negative electrode tab 27 Conductive layer 100 Energy Storage Devices 220 Electrode body 222 Positive electrode 222a Positive electrode current collector 222b Cathode active material layer 222b1 End face 222b2 side 222t positive electrode tab 223 Separator 227 Conductive layer

Claims

1. A first electrode having a first current collector and a first active material layer provided on the first current collector; second electrode; A separator that separates the first electrode and the second electrode; and, A conductive layer is provided between the first active material layer and the separator, extending from the surface of the first active material layer to the first current collector. Equipped with, Energy storage device.

2. The first current collector comprises a rectangular sheet-shaped main body and a first tab protruding outward from a first side of the main body. The conductive layer is provided on the first side, extending from the surface of the first active material layer to the first tab. The energy storage device according to claim 1.

3. The conductive layer is provided on the surface of the separator. The energy storage device according to claim 1 or 2.

4. The conductive layer is bonded to the first current collector. The energy storage device according to claim 3.

5. The conductive layer is provided on the surface of the first active material layer. The energy storage device according to claim 1 or 2.

6. The conductive layer covers at least a portion of the end face in the thickness direction of the first active material layer and at least a portion of the side surface along the same direction. The energy storage device according to claim 5.

7. The conductive layer is a metal vapor-deposited layer. The energy storage device according to claim 1 or 2.

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