Anode and battery including said anode

Abstract

To provide a technique for obtaining a battery with suitably improved reliability.SOLUTION: In a preferred aspect of a negative electrode disclosed herein, a negative electrode 24 includes a negative electrode current collector 24c made of copper, and a negative electrode active material layer 24a formed on the negative electrode current collector 24c. A negative electrode tab 24t is present in a part of the periphery of the negative electrode current collector 24c, and on at least one side of the negative electrode tab 24t, a metal film 27 made of a metal species whose laser absorption rate at wavelengths of 1 μm or more is higher than that of copper is formed.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present disclosure relates to a negative electrode and a battery including the negative electrode. [Background technology]

[0002] In recent years, batteries such as lithium ion secondary batteries have been suitably used as portable power sources for personal computers, mobile terminals, and the like, and as power sources for driving vehicles such as electric vehicles (BEVs), hybrid vehicles (HEVs), and plug-in hybrid vehicles (PHEVs). A negative electrode current collector made of copper is typically used in the negative electrode of such batteries. For example, Patent Documents 1 and 2 below disclose such a negative electrode current collector. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-022306 A [Patent Document 2] JP 2009-117267 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, as this type of negative electrode current collector, a configuration in which a current collecting tab is formed is known. The formation of such a tab is performed, for example, by laser processing. In addition, a laser having a wavelength of 1 μm or more is generally used for such laser processing. On the other hand, according to the study by the present inventor, it was found that, for example, a negative electrode current collector made of copper has a low laser absorption rate at a wavelength of 1 μm or more and tends to be insufficient in processability, which may cause burrs during laser processing. And, for example, if such burrs peel off, they may be mixed into the battery as foreign matter, which may cause malfunctions in the battery, and this is not preferable.

[0005] The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a technique for obtaining a battery with suitably improved reliability. [Means for solving the problem]

[0006] In order to achieve this object, the present disclosure provides a copper foil for a negative electrode current collector, in which a metal film made of a metal species having a higher laser absorptivity at wavelengths of 1 μm or more than copper is formed on a part of the periphery of at least one side of the copper foil for a negative electrode current collector. The copper foil for a negative electrode current collector having such a configuration can favorably improve the processability of the tab during laser processing. This favorably suppresses the generation of burrs during laser processing, thereby making it possible to obtain a highly reliable negative electrode (and a battery including the negative electrode).

[0007] In a preferred embodiment of the copper foil for a negative electrode current collector disclosed herein, the metal film is formed on a part of the periphery on both sides of the copper foil for a negative electrode current collector. This configuration is preferable because it can improve the working efficiency when forming the tab.

[0008] In a preferred embodiment of the copper foil for negative electrode current collector disclosed herein, the metal film is composed of at least one selected from the group consisting of aluminum, nickel, and molybdenum. Such metal species have a higher laser absorptivity at wavelengths of 1 μm or more than copper and are highly versatile, so they can be preferably used in the technology disclosed herein.

[0009] In one embodiment of the copper foil for a negative electrode current collector disclosed herein, the width of the metal film is 5 mm or more.

[0010] In a preferred embodiment of the copper foil for a negative electrode current collector disclosed herein, the metal film is formed in a convex shape so that the ratio (S / T) of the thickness S of the metal film to the thickness T of the copper foil for a negative electrode current collector is 0.05 to 0.3 in a cross-sectional view of the copper foil for a negative electrode current collector. By setting the ratio (S / T) within the above range, the processability of the tab can be more suitably improved.

[0011] In one embodiment of the copper foil for a negative electrode current collector disclosed herein, the portion on which the metal film is formed can be used to form a tab.

[0012] In another aspect, the present disclosure provides a method for producing the copper foil for a negative electrode current collector disclosed herein. The method for producing the copper foil for a negative electrode current collector includes the following steps: a step of preparing a copper foil; and a step of forming a metal film made of a metal species having a higher laser absorptivity at wavelengths of 1 μm or more than copper on a part of the periphery of at least one side of the copper foil. According to this production method, it is possible to obtain a copper foil for a negative electrode current collector that can suitably improve the processability of the tab during laser processing.

[0013] In another aspect, the present disclosure provides a negative electrode comprising a negative electrode current collector made of copper and a negative electrode active material layer formed on the negative electrode current collector, a tab being present on a part of the periphery of the negative electrode current collector, and a metal film made of a metal species having a higher laser absorptivity at wavelengths of 1 μm or more than copper being formed on at least one surface of the tab.

[0014] In one embodiment of the negative electrode disclosed herein, the metal film is formed on both sides of the tab. Also, in one embodiment of the negative electrode disclosed herein, the metal film is made of at least one selected from the group consisting of aluminum, nickel, and molybdenum.

[0015] In another aspect, a battery is provided that includes any of the negative electrodes disclosed herein. The battery includes a negative electrode in which burrs are suitably suppressed from being generated during laser processing. Therefore, a highly reliable battery can be provided. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a perspective view showing a battery according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic vertical cross-sectional view taken along line II-II in FIG. [Diagram 3] FIG. 4 is a perspective view showing a schematic view of an electrode assembly attached to a sealing plate. [Figure 4] FIG. 2 is a perspective view showing a schematic view of one electrode body. [Diagram 5] FIG. 2 is a schematic diagram showing the configuration of an electrode body. [Figure 6] FIG. 1 is a flow diagram showing a method for producing a copper foil for a negative electrode current collector according to one embodiment. [Figure 7] FIG. 6 is a schematic diagram showing the configuration of a copper foil for a negative electrode current collector for producing a negative electrode included in the electrode body of FIG. 5. [Figure 8] 8 is a schematic cross-sectional view taken along line VIII-VIII in FIG. 7. [Figure 9] 6 is a schematic diagram showing the configuration of a negative electrode included in the electrode assembly of FIG. 5. [Figure 10] 10 is a schematic cross-sectional view taken along line XX in FIG. 9. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, some preferred 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 implementing the present disclosure (for example, the general configuration and manufacturing process of a battery that does not characterize the present disclosure) can be understood as design matters of a person skilled in the art based on the conventional technology in the field. The present disclosure can be implemented based on the contents disclosed in this specification and the technical common sense in the field. In addition, the following description is not intended to limit the technology disclosed herein to the following embodiments. Note that the expression "A to B" indicating a range in this specification includes the meaning of A or more and B or less, as well as the meaning of more than A and less than B.

[0018] In this specification, the term "battery" refers to any power storage device capable of extracting electrical energy, and is a concept that includes primary batteries and secondary batteries. In addition, in this specification, the term "secondary battery" refers to any power storage device capable of repeated charging and discharging, and is a concept that includes so-called storage batteries (chemical batteries) such as lithium ion secondary batteries and nickel metal hydride batteries, and capacitors (physical batteries) such as electric double layer capacitors.

[0019] <Battery configuration> Fig. 1 is a perspective view of the battery 100. Fig. 2 is a schematic longitudinal sectional view taken along line II-II in Fig. 1. In the following description, the symbols L, R, F, Rr, U, and D in the drawings represent left, right, front, rear, top, and bottom, and the symbols X, Y, and Z in the drawings represent the short side direction, long side direction perpendicular to the short side direction, and up-down direction of the battery 100, respectively. However, these directions are merely for the convenience of description, and do not limit the installation form of the battery 100 in any way.

[0020] 2, the battery 100 includes a battery case 10, an electrode assembly 20, a positive electrode terminal 30, a negative electrode terminal 40, a positive electrode current collector 50, a negative electrode current collector 60, and a nonaqueous electrolyte (not shown). The battery 100 here is a lithium ion secondary battery.

[0021] The battery case 10 is a housing that contains the electrode assembly 20 and the nonaqueous electrolyte. Here, the battery case 10 has a flat, bottomed rectangular parallelepiped (rectangular) outer shape. However, the battery case 10 may be cylindrical or bag-shaped. The material of the battery case 10 may be the same as that used conventionally, and is not particularly limited. The battery case 10 is preferably made of metal, and more preferably made of, for example, aluminum, aluminum alloy, iron, iron alloy, or the like. The battery case 10 may be an aluminum laminate film having a metal layer containing aluminum and a fusion layer containing resin. As shown in FIG. 2, the battery case 10 includes an exterior body 12 having an opening 12h and a sealing plate (lid body) 14 that seals the opening 12h. As in this embodiment, the battery case 10 preferably includes an exterior body 12 having an opening 12h and a sealing plate 14 that seals the opening 12h.

[0022] As shown in FIG. 1, the exterior body 12 includes a bottom wall 12a, a pair of long side walls 12b extending from the bottom wall 12a and facing each other, and a pair of short side walls 12c extending from the bottom wall 12a and facing each other. The bottom wall 12a is substantially rectangular. The bottom wall 12a faces the opening 12h. The area of ​​the short side walls 12c is smaller than the area of ​​the long side walls 12b. The sealing plate 14 is attached to the exterior body 12 so as to close the opening 12h of the exterior body 12. The sealing plate 14 faces the bottom wall 12a of the exterior body 12. The sealing plate 14 is substantially rectangular in plan view. The battery case 10 is integrated by joining (for example, welding) the sealing plate 14 to the periphery of the opening 12h of the exterior body 12. The battery case 10 is hermetically sealed (sealed).

[0023] As shown in FIG. 2, the sealing plate 14 is provided with a liquid inlet 15, a discharge valve 17, and two terminal outlet holes 18 and 19. The liquid inlet 15 is for injecting a nonaqueous electrolyte after the sealing plate 14 is assembled to the exterior body 12. The liquid inlet 15 is sealed by a sealing member 16. The discharge valve 17 is configured to break when the pressure inside the battery case 10 reaches a predetermined value or more, and to discharge the gas inside the battery case 10 to the outside. The terminal outlet holes 18 and 19 are formed at both ends of the sealing plate 14 in the direction Y. The terminal outlet holes 18 and 19 penetrate the sealing plate 14 in the vertical direction Z. The terminal outlet holes 18 and 19 each have an inner diameter large enough to insert the positive electrode terminal 30 and the negative electrode terminal 40 before being attached to the sealing plate 14 (before being crimped).

[0024] The non-aqueous electrolyte may be the same as that of the conventional electrolyte, and is not particularly limited. The non-aqueous electrolyte contains a non-aqueous solvent and a supporting salt (electrolyte salt). The non-aqueous electrolyte may further contain additives as necessary. The non-aqueous solvent contains, for example, carbonates such as ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. The non-aqueous solvent preferably contains carbonates. In particular, it is preferable that the non-aqueous solvent contains a cyclic carbonate and a chain carbonate. The supporting salt is, for example, a fluorine-containing lithium salt such as lithium hexafluorophosphate (LiPF6).

[0025] The positive electrode terminal 30 is disposed at one end of the sealing plate 14 in the direction Y (the left end in FIG. 1 and FIG. 2). The negative electrode terminal 40 is disposed at the other end of the sealing plate 14 in the direction Y (the right end in FIG. 1 and FIG. 2). As shown in FIG. 2, the positive electrode terminal 30 and the negative electrode terminal 40 extend from the inside to the outside of the sealing plate 14 through the terminal drawing holes 18 and 19. The positive electrode terminal 30 and the negative electrode terminal 40 are fixed to the sealing plate 14. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are crimped to the peripheral portion surrounding the terminal drawing holes 18 and 19 of the sealing plate 14 by crimping. The crimped portions 30c and 40c are formed at the ends of the positive electrode terminal 30 and the negative electrode terminal 40 on the side of the exterior body 12 (the lower end in FIG. 2).

[0026] As shown in Fig. 2, the positive electrode terminal 30 is electrically connected to the positive electrode 22 (see Fig. 5) of the electrode assembly 20 via a positive electrode current collector 50 inside the exterior body 12. The negative electrode terminal 40 is electrically connected to the negative electrode 24 (see Fig. 5) of the electrode assembly 20 via a negative electrode current collector 60 inside the exterior body 12. The positive electrode terminal 30 is insulated from the sealing plate 14 by an internal insulating member 80 and a gasket 90. The negative electrode terminal 40 is insulated from the sealing plate 14 by an internal insulating member 80 and a gasket 90.

[0027] A plate-shaped positive electrode external conductive member 32 and a plate-shaped negative electrode external conductive member 42 are attached to the outer surface of the sealing plate 14. The positive electrode external conductive member 32 is electrically connected to the positive electrode terminal 30. The negative electrode external conductive member 42 is electrically connected to the negative electrode terminal 40. The positive electrode external conductive member 32 and the negative electrode external conductive member 42 are members to which bus bars are attached when electrically connecting multiple batteries 100 to each other. The positive electrode external conductive member 32 and the negative electrode external conductive member 42 are insulated from the sealing plate 14 by an external insulating member 92.

[0028] FIG. 3 is a perspective view that shows a schematic diagram of the electrode assembly group 20 attached to the sealing plate 14. The electrode assembly group 20 has a plurality of electrode assemblies. The electrode assembly group 20 has three electrode assemblies 20a, 20b, and 20c here. However, the number of electrode assemblies arranged inside one exterior body 12 is not particularly limited, and may be, for example, one, two, or four or more. The electrode assemblies 20a, 20b, and 20c here are electrically connected in parallel. The electrode assemblies 20a, 20b, and 20c are arranged side by side in the short side direction X. The electrode assemblies 20a, 20b, and 20c each have a flattened outer shape. The electrode assemblies 20a, 20b, and 20c here are each wound electrode assemblies. The electrode assemblies 20a, 20b, and 20c are each arranged inside the battery case 10 with the winding axis WL (see FIG. 5) oriented substantially parallel to the direction Y. An end face of the electrode body 20a perpendicular to the winding axis WL (in other words, the lamination surface where the positive electrodes 22 and the negative electrodes 24 are laminated) faces the short side wall 12c.

[0029] FIG. 4 is a perspective view showing the electrode body 20a. In the following, the electrode body 20a will be described in detail as an example, but the electrode bodies 20b and 20c can have a similar configuration. The electrode body 20a has a pair of curved portions (R portions) 20r and a flat portion 20f connecting the pair of curved portions 20r. One curved portion 20r (upper side of FIG. 4) faces the sealing plate 14, and the other curved portion 20r (lower side of FIG. 4) faces the bottom wall 12a of the exterior body 12. The flat portion 20f faces the long side wall 12b of the exterior body 12. In the electrode bodies 20a, 20b, and 20c adjacent to each other in the short side direction X, the flat portions 20f face each other.

[0030] 5 is a schematic diagram showing the configuration of the electrode body 20a. The electrode body 20a has a positive electrode 22, a negative electrode 24, and a separator 26. In this embodiment, the electrode body 20a is configured by stacking a strip-shaped positive electrode 22 and a strip-shaped negative electrode 24 with a strip-shaped separator 26 interposed therebetween, and winding the stack around a winding axis WL. The winding axis WL direction is substantially parallel to the direction Y. However, in other embodiments, the electrode body 20a may be a laminated electrode body in which multiple square-shaped (e.g., rectangular) positive electrodes and multiple square-shaped (e.g., rectangular) negative electrodes are stacked in an insulated state.

[0031] The positive electrode 22 may be the same as a conventional one, and is not particularly limited. As shown in FIG. 5, the positive electrode 22 has a positive electrode collector 22c, and a positive electrode active material layer 22a and a positive electrode protective layer 22p fixed on at least one surface of the positive electrode collector 22c. However, the positive electrode protective layer 22p is not essential and can be omitted in other embodiments. The positive electrode collector 22c is strip-shaped. The positive electrode collector 22c is preferably made of metal, and more preferably made of metal foil. Here, the positive electrode collector 22c is aluminum foil.

[0032] A plurality of positive electrode tabs 22t are provided at one end of the positive electrode collector 22c in the direction Y (the left end in FIG. 5). The plurality of positive electrode tabs 22t protrude toward one side in the direction Y (the left side in FIG. 5). The plurality of positive electrode tabs 22t protrude in the direction Y beyond the separator 26. The positive electrode tab 22t is a part of the positive electrode collector 22c here, and is made of metal foil (aluminum foil). The positive electrode tab 22t has a portion (current collector exposed portion) where the positive electrode active material layer 22a and the positive electrode protective layer 22p of the positive electrode collector 22c are not formed. As shown in FIG. 2 to FIG. 4, the plurality of positive electrode tabs 22t are stacked at one end of the direction Y (the left end in FIG. 2 to FIG. 4) to form a positive electrode tab group 23. The positive electrode tab group 23 is electrically connected to the positive electrode terminal 30 via the positive electrode collector 50. A positive electrode second current collecting portion 52, which will be described later, is attached to the positive electrode tab group 23.

[0033] As shown in FIG. 5, the positive electrode active material layer 22a is provided in a strip shape along the longitudinal direction of the positive electrode current collector 22c. The positive electrode active material layer 22a contains a positive electrode active material capable of reversibly absorbing and releasing charge carriers. The positive electrode active material preferably contains a lithium transition metal composite oxide. Specific examples include lithium cobalt oxide, lithium manganate, lithium nickel oxide, lithium nickel manganese composite oxide, lithium nickel cobalt composite oxide, and lithium nickel cobalt manganese composite oxide. The positive electrode active material layer 22a may contain any component other than the positive electrode active material, such as a binder, a conductive material, and various additive components. For example, polyvinylidene fluoride (PVDF) or the like can be used as the binder. For example, a carbon material such as acetylene black (AB) can be used as the conductive material.

[0034] As shown in Fig. 5, the positive electrode protective layer 22p is provided at the boundary between the positive electrode current collector 22c and the positive electrode active material layer 22a in the direction Y. The positive electrode protective layer 22p is provided in a strip shape along the positive electrode active material layer 22a. The positive electrode protective layer 22p contains an inorganic filler (e.g., alumina). The positive electrode protective layer 22p may contain any component other than the inorganic filler, such as a conductive material, a binder, various additive components, and the like. The conductive material and the binder may be the same as those exemplified as those that may be contained in the positive electrode active material layer 22a.

[0035] Next, the negative electrode 24 according to this embodiment will be described. FIG. 9 is a schematic diagram showing the configuration of the negative electrode 24 included in the electrode body 20a. FIG. 10 is a schematic cross-sectional view of the negative electrode of FIG. 9 taken along the line XX. As shown in FIG. 9, the negative electrode 24 includes a strip-shaped negative electrode collector 24c made of copper, and a negative electrode active material layer 24a formed on the negative electrode collector 24c. Here, "made of copper" can mean an embodiment in which, when the total mass of the components constituting the negative electrode collector 24c is taken as 100 mass%, copper (Cu) is included in an amount of 90 mass% or more, 95 mass% or more, 99 mass% or more, or 99.5 mass% or more (may be 100 mass%). Examples of components other than copper include other metal components such as nickel (Ni).

[0036] As shown in FIG. 9, the negative electrode current collector 24c has a negative electrode tab 24t on a part of its periphery (here, a pair of short sides and a pair of long sides are shown). The negative electrode current collector 24c has a plurality of negative electrode tabs 24t formed intermittently along its long side direction (Z direction in FIG. 9). A plurality of negative electrode tabs 24t are provided on one end (right end in FIG. 5) in the direction Y of the negative electrode current collector 24c. The plurality of negative electrode tabs 24t protrude toward one side in the direction Y (right side in FIG. 5). The plurality of negative electrode tabs 24t protrude in the direction Y beyond the separator 26. The plurality of negative electrode tabs 24t protrude in the direction Y beyond the separator 26. Here, the negative electrode tab 24t is a part of the negative electrode current collector 24c, and is made of metal foil (copper foil). As shown in Figs. 2 to 4, the negative electrode tabs 24t are stacked at one end in direction Y (the right end in Figs. 2 to 4) to form a negative electrode tab group 25. The negative electrode tab group 25 is provided at a position symmetrical to the positive electrode tab group 23 in direction Y. The negative electrode tab group 25 is electrically connected to the negative electrode terminal 40 via a negative electrode current collecting part 60. A negative electrode second current collecting part 62, which will be described later, is attached to the negative electrode tab group 25.

[0037] As shown in FIG. 10, a metal film 27 is formed on at least one side (both sides in this case) of the negative electrode tab 24t. The metal film 27 is composed of a metal species having a higher laser absorptance at wavelengths of 1 μm or more than copper. Here, "composed of metal species" may mean an embodiment in which, when the total mass of the components constituting the metal film 27 is taken as 100 mass%, the metal species is contained in an amount of, for example, 90 mass% or more, 95 mass% or more, or 99 mass% or more, or 99.5 mass% or more (may be 100 mass%). Examples of such metal species include aluminum (Al), nickel (Ni), molybdenum (Mo), and carbon copper. As the metal species constituting the metal film 27, one type may be used alone, or two or more types may be used in combination. In addition, from the viewpoint of high versatility, it is preferable that the metal species constituting the metal film 27 includes at least one of aluminum, nickel, and molybdenum. The above-mentioned laser absorptance may mean a value measured using, for example, a spectrophotometer. A commercially available spectrophotometer can be used as such a spectrophotometer, and the measurement conditions can be determined according to the catalog. As described above, in this embodiment, the metal film 27 is formed on both sides of the negative electrode tab 24t. However, in other embodiments, the metal film 27 may be formed only on one side of the negative electrode tab 24t. As shown in FIG. 9, in this embodiment, the metal film 27 is formed on a part of the negative electrode tab 24t (in other words, the negative electrode tab 24t includes the metal film 27 and the negative electrode active material layer 24a). However, in other embodiments, the metal film 27 may be formed on the entire surface of the negative electrode tab 24t.

[0038] 9, when the width of the negative electrode tab 24t in the protruding direction (Y direction in FIG. 9) is Q and the width of the metal film 27 in the protruding direction is R, the ratio (R / Q) of the width R to the width Q can be within a range of approximately 0.2 to 1.0 (e.g., 0.5 to 0.8), but is not limited thereto.

[0039] As shown in FIG. 9, the negative electrode active material layer 24a is provided in a strip shape along the long side direction (Z direction in FIG. 9) of the negative electrode current collector 24c. The negative electrode active material layer 24a contains a negative electrode active material capable of reversibly absorbing and releasing charge carriers. Examples of the negative electrode active material include carbon materials such as natural graphite, artificial graphite, hard carbon, soft carbon, and amorphous carbon, silicon-based materials, and mixtures thereof. The negative electrode active material preferably contains graphite. Also, as shown in FIG. 10, the negative electrode active material layer 24a is formed so as to overlap a part of the metal film 27 here. However, in other embodiments, the negative electrode active material layer 24a may be formed so as not to overlap the metal film 27.

[0040] 10, when the thickness of the negative electrode active material layer 24a is U and the thickness of the metal film 27 is S, the ratio (S / U) of the thickness S to the thickness U can be generally 0.001 to 1.0 (preferably 0.005 to 0.05), but is not limited thereto.

[0041] The negative electrode active material layer 24a may contain any component other than the negative electrode active material, such as a binder, a thickener, a dispersant, a conductive material, various additive components, etc. The negative electrode active material layer 24a preferably contains a binder. As the binder, for example, rubbers such as styrene butadiene rubber (SBR), acrylic resins such as polyacrylic acid (PAA), and celluloses such as carboxymethyl cellulose (CMC) can be used. CMC can also be used as a thickener, dispersant, etc.

[0042] Returning to FIG. 5, the separator 26 is disposed between the positive electrode 22 and the negative electrode 24. The separator 26 is a member that insulates the positive electrode active material layer 22a of the positive electrode 22 from the negative electrode active material layer 24a of the negative electrode 24. For example, a resin porous sheet made of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable as the separator 26. The separator 26 may have a base layer made of a resin porous sheet and an adhesive layer containing a binder formed on at least one surface of the base layer. In this case, the separator 26 is preferably bonded to at least one of the positive electrode 22 and the negative electrode 24 via the adhesive layer.

[0043] 2, the positive electrode current collecting part 50 constitutes a conductive path that electrically connects the positive electrode tab group 23 consisting of the multiple positive electrode tabs 22t to the positive electrode terminal 30. The positive electrode current collecting part 50 includes a positive electrode first current collecting part 51 and a positive electrode second current collecting part 52. The positive electrode first current collecting part 51 and the positive electrode second current collecting part 52 may be made of the same metal type as the positive electrode current collector 22c, for example, a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel.

[0044] The positive electrode first current collecting part 51 is attached to the inner surface of the sealing plate 14. Here, the positive electrode first current collecting part 51 is fixed to the sealing plate 14 by crimping. The positive electrode first current collecting part 51 has a first region that spreads horizontally along the inner surface of the sealing plate 14, and a second region that extends from one end of the first region in the long side direction Y (the left end in FIG. 2) toward the short side wall 12c of the exterior body 12. In the first region, a through hole (not shown) that penetrates in the vertical direction Z is formed at a position corresponding to the terminal pull-out hole 18 of the sealing plate 14. The first region is electrically connected to the positive electrode terminal 30 by crimping. The first region is insulated from the sealing plate 14 by the internal insulating member 80. The second region extends along the vertical direction Z.

[0045] The positive electrode second current collecting portion 52 extends along the short side wall 12c of the exterior body 12. As shown in Fig. 3 and Fig. 4, the positive electrode second current collecting portion 52 is attached to the electrode body 20a. The positive electrode second current collecting portion 52 has a current collecting plate connection portion 52a electrically connected to the second region of the positive electrode first current collecting portion 51, a tab joint portion 52c attached to the positive electrode tab group 23 and electrically connected to the multiple positive electrode tabs 22t, and a connection portion 52b connecting the current collecting plate connection portion 52a and the tab joint portion 52c.

[0046] The current collector plate connection portion 52a extends along the up-down direction Z. The current collector plate connection portion 52a is provided with a recess 52d that is thinner than the surrounding area. The recess 52d is provided with a through hole 52e that penetrates in the short side direction X. A joint with the positive electrode first current collector portion 51 is formed in the through hole 52e. The joint is a welded joint formed by welding such as ultrasonic welding, resistance welding, laser welding, etc. The tab joint 52c extends along the up-down direction Z. The tab joint 52c is provided with a joint with the positive electrode tab group 23. The joint is a welded joint formed by welding such as ultrasonic welding, resistance welding, laser welding, etc. with a plurality of positive electrode tabs 22t overlapping each other.

[0047] As shown in FIG. 2, the negative electrode current collecting part 60 constitutes a conductive path that electrically connects the negative electrode tab group 25 consisting of a plurality of negative electrode tabs 24t and the negative electrode terminal 40. The negative electrode current collecting part 60 includes a negative electrode first current collecting part 61 and a negative electrode second current collecting part 62. The negative electrode first current collecting part 61 and the negative electrode second current collecting part 62 may be made of the same metal type as the negative electrode current collector 24c, for example, a conductive metal such as copper, a copper alloy, nickel, or stainless steel. The configurations of the negative electrode first current collecting part 61 and the negative electrode second current collecting part 62 may be the same as those of the positive electrode first current collecting part 51 and the positive electrode second current collecting part 52 of the positive electrode current collecting part 50.

[0048] 4, the negative electrode second current collecting portion 62 has a current collecting plate connection portion 62a electrically connected to the negative electrode first current collecting portion 61, a tab joint portion 62c attached to the negative electrode tab group 25 and electrically connected to the plurality of negative electrode tabs 24t, and a connection portion 62b connecting the current collecting plate connection portion 62a and the tab joint portion 62c. The current collecting plate connection portion 62a has a recess 62d connected to the tab joint portion 62c. The recess 62d is provided with a through hole 62e penetrating in the short side direction X.

[0049] <Battery manufacturing method> Next, an example of a method for manufacturing the battery 100 will be described. The method for manufacturing the battery 100 is characterized by the method for manufacturing the negative electrode 24. Other than the manufacturing of the negative electrode 24, the manufacturing process can be carried out according to a conventionally known manufacturing method for this type of battery. An example of a method for manufacturing the negative electrode 24 will be described below.

[0050] The method for producing the negative electrode 24 according to this embodiment roughly includes the steps of producing the copper foil 24C for the negative electrode current collector, forming the negative electrode active material layer 24a, and forming the negative electrode tab 24t. Each step will be described below.

[0051] First, the preparation of the copper foil 24C for the negative electrode current collector will be described. Here, FIG. 6 is a flow diagram showing the manufacturing method of the copper foil 24C for the negative electrode current collector according to this embodiment. FIG. 7 is a schematic diagram showing the configuration of the copper foil 24C for the negative electrode current collector. FIG. 8 is a schematic cross-sectional view along the line VIII-VIII of the copper foil 24C for the negative electrode current collector shown in FIG. 7. As shown in FIG. 6, the copper foil 24A is prepared (preparation step: step S1). In this embodiment, a strip-shaped copper foil 24A is prepared. Then, a metal film 27 made of a metal species having a higher laser absorption rate at a wavelength of 1 μm or more than copper is formed on a part of the periphery (here, a pair of short sides and a pair of long sides) on at least one side (here, both sides) of the copper foil 24A (formation step; step S2). The metal film 27 is made of the metal species as described above. Examples of the method for forming the metal film 27 include plating methods such as electroplating, hot-dip plating, and electroless plating, sputtering, and vapor deposition. These various methods can be carried out according to conventionally known methods. In this way, a copper foil 24C for a negative electrode current collector can be produced in which a metal film 27 made of a metal species having a higher laser absorption rate at wavelengths of 1 μm or more than copper is formed on at least a part of the periphery on one side of the copper foil 24A (here, on one of the pair of long sides). The copper foil 24C for a negative electrode current collector having such a configuration can suitably improve the processability of the tab during laser processing (in other words, the copper foil 24C for a negative electrode current collector can be suitably used to form the negative electrode tab 24t). This suitably suppresses the generation of burrs during laser processing, so that a highly reliable negative electrode 24 (and a battery 100 including the negative electrode 24) can be obtained.

[0052] As shown in FIG. 7, in this embodiment, the metal film 27 is formed on one of a pair of long sides of the copper foil 24C for the negative electrode current collector. This configuration is preferable because it can improve the work efficiency when forming the negative electrode tab 24t. Alternatively, the metal film 27 may be formed on the edge of the pair of long sides of the copper foil 24C for the negative electrode current collector. In this case, two sheets of the copper foil 24C for the negative electrode current collector can be obtained by cutting the center of the copper foil 24A with a cutter or the like. In another embodiment, the metal film 27 may be formed on only one side of the copper foil 24C for the negative electrode current collector. In another embodiment, the metal film 27 may be formed on the edge of the short side of the copper foil 24A. In addition, as shown in FIG. 8, the metal film 27 is formed so as to be convex with respect to the copper foil 24A. In one embodiment, when the thickness of the metal film 27 is S and the thickness of the copper foil 24A is T, the ratio (S / T) of the thickness S to the thickness T can be, for example, 0.01 to 1.0, and from the viewpoint of more suitably improving the processability of the negative electrode tab 24t, can be preferably 0.02 to 0.5, and more preferably 0.05 to 0.3. In addition, when the width in the direction Y of the metal film 27 provided on the copper foil 24C for a negative electrode current collector is P as shown in Fig. 7, the width P may be, for example, 5 mm or more, 10 mm or more, 20 mm or more, 30 mm or more, or 40 mm or more.

[0053] Next, the negative electrode active material layer 24a is formed on at least one side (both sides in this case) of the copper foil 24C for the negative electrode current collector prepared as described above. The negative electrode active material layer 24a can be formed, for example, by applying a slurry for forming a negative electrode active material layer to a desired region of the copper foil 24C for the negative electrode current collector and drying it. In this embodiment, as shown in FIG. 10, the negative electrode active material layer 24a is formed on both sides of the copper foil 24C for the negative electrode current collector. In this embodiment, the negative electrode active material layer 24a is formed so that a part of the negative electrode active material layer 24a overlaps the metal film 27. However, in other embodiments, the metal film 27 and the negative electrode active material layer 24a may be formed so as not to overlap each other.

[0054] Next, in the region including the portion where the metal film 27 of the copper foil 24C for the negative electrode current collector is formed, a plurality of negative electrode tabs 24t are formed along the long side direction (Z direction in FIG. 7) of the copper foil 24C for the negative electrode current collector. The formation of the negative electrode tabs 24t can be performed by laser irradiation or the like. The copper foil 24C for the negative electrode current collector is particularly suitable as a target for laser irradiation using a laser having a wavelength of 1 μm or more (for example, a YAG laser or a fiber laser). In this embodiment, in addition to the portion where the metal film 27 is formed, the overlapping portion formed so that the metal film 27 and the negative electrode active material layer 24a overlap is also irradiated with laser when forming the negative electrode tabs 24t. Since the overlapping portion includes the metal film 27a, it has excellent laser processability. In the above manner, the negative electrode 24 shown in FIG. 9 can be produced.

[0055] Battery 100 can be used for various purposes, but can be suitably used, for example, as a power source (driving power source) for a motor mounted on a vehicle such as a passenger car, truck, etc. The type of vehicle is not particularly limited, but examples include a plug-in hybrid electric vehicle (PHEV), a hybrid electric vehicle (HEV), a battery electric vehicle (BEV), etc.

[0056] As described above, specific aspects of the technology disclosed herein include those described in the following items. Item 1: A negative electrode comprising a negative electrode current collector made of copper and a negative electrode active material layer formed on the negative electrode current collector, wherein a tab is present on a part of a periphery of the negative electrode current collector, and a metal film made of a metal species having a higher laser absorptivity at wavelengths of 1 μm or more than copper is formed on at least one surface of the tab. Item 2: The negative electrode according to item 1, wherein the metal film is formed on both sides of the tab. Item 3: The negative electrode according to item 1 or 2, wherein the metal film is made of at least one selected from the group consisting of aluminum, nickel, and molybdenum. Item 4: A copper foil for a negative electrode current collector, the copper foil for a negative electrode current collector having a metal film formed on a part of a periphery on at least one surface of the copper foil for a negative electrode current collector, the metal film being made of a metal species having a higher laser absorptivity at wavelengths of 1 μm or more than copper. Item 5: The copper foil for a negative electrode current collector according to item 4, wherein the metal film is formed on part of the periphery on both sides of the copper foil for a negative electrode current collector. Item 6: The copper foil for a negative electrode current collector according to item 4 or 5, wherein the metal film is made of at least one selected from the group consisting of aluminum, nickel, and molybdenum. Item 7: The copper foil for a negative electrode current collector according to any one of items 4 to 6, wherein the metal film has a width of 5 mm or more. Item 8: The copper foil for a negative electrode current collector according to any one of Items 4 to 7, wherein the metal film is formed in a convex shape so that a ratio (S / T) of a thickness S of the metal film to a thickness T of the copper foil for a negative electrode current collector is 0.05 to 0.3 in a cross-sectional view of the copper foil for a negative electrode current collector. Item 9: The copper foil for a negative electrode current collector according to any one of items 4 to 8, wherein the portion on which the metal film is formed is used for forming a tab. Item 10: A method for producing a copper foil for a negative electrode current collector, comprising the steps of: preparing a copper foil; and forming a metal film made of a metal species having a higher laser absorptivity at wavelengths of 1 μm or more than copper on a part of the periphery of at least one side of the copper foil. Item 11: A battery comprising the negative electrode according to any one of items 1 to 3.

[0057] Test examples relating to the negative electrode disclosed herein will be described below, but it is not intended that the present disclosure be limited to such test examples.

[0058] <Preparation of copper foil for negative electrode current collector according to Examples 1 to 5> A metal film (thickness: 1.0 μm) was formed on copper foil (electrolytic copper foil, length 200 mm × width 250 mm × thickness 10 μm) for a negative electrode current collector by electrolytic plating. Here, the metal species constituting the metal film and the location where the metal film was formed in each example were as shown in the corresponding column in Table 1. Here, the "end" in Table 1 indicates an area 6 mm from the end of one of a pair of short sides of the copper foil. Also, the metal film is formed on the ends on both sides of the copper foil. And, since no metal film was formed in Example 3, it is indicated as "-". It is known that the laser absorptance at wavelengths of 1 μm or more measured by a spectrophotometer is higher for nickel (Ni) and aluminum (Al) than for copper (Cu), and lower for silver (Ag) than for copper.

[0059] <Laser processability evaluation> The copper foil for negative electrode current collector according to each example prepared as described above was cut by scanning a YAG laser (wavelength: 1.064 μm) along its long side direction. The cut surface was checked for the presence or absence of burrs, and if burrs were found, their lengths were measured. If no burrs were found, or if burrs were found, but the length of the burrs was less than 200 μm, the laser processability was evaluated as "good", and if the length of the burrs was 200 μm or more, the laser processability was evaluated as "poor". The results are shown in the corresponding columns in Table 1.

[0060] <Preparation of Lithium-ion Secondary Batteries for Evaluation According to Examples 1 to 5> (Preparation of negative electrode plate) Graphite as the negative electrode active material, styrene butadiene rubber (SBR) as the binder, and carboxymethyl cellulose (CMC) as the thickener were mixed in a 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 to the copper foil for the negative electrode current collector according to each example prepared as described above in a weight ratio of 7 mg / cm. 2The coating was performed so that the coated end was overlapped with the metal film by 1 mm. After that, the negative electrode plate was obtained by drying and roll pressing. Then, a YAG laser (wavelength: 1.064 μm) was scanned on the end of the negative electrode plate according to each example to form a tab. In this way, the negative electrode plate according to each example was produced.

[0061] (Preparation 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 in a ratio of 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 positive electrode active material layer forming slurry. This positive electrode active material layer forming slurry was applied to an aluminum foil positive electrode current collector with a basis weight of 10 mg / cm. 2 The coating was applied so that the thickness of the positive electrode plate was 100 μm. After that, drying and roll pressing were performed to obtain a positive electrode plate. Then, a tab was formed on the positive electrode plate according to each example by laser scanning. In this manner, the positive electrode plate according to each example was produced.

[0062] A microporous polyethylene sheet having a thickness of 16 μm and a single layer structure of PE was prepared as a separator. The positive electrode plate and the negative electrode plate were laminated with the separator interposed therebetween to obtain a laminated electrode body.

[0063] Next, a current collector was welded to the laminated electrode body, and the laminated electrode body was housed in a laminate film and a non-aqueous electrolyte was poured in. The non-aqueous electrolyte was prepared by dissolving LiPF6 as a supporting salt at a concentration of 1.0 mol / L 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. The laminate film was then sealed to obtain a lithium ion secondary battery (capacity: 1 Ah) for evaluation according to each example.

[0064] <Initial charging and aging process> The lithium-ion secondary battery for evaluation was subjected to an initial charging process in a 25°C environment, where the battery was charged at a constant current of 1C up to 4.1V, and the SOC (State of Charge) was fully charged (SOC 100%). Then, an aging process was performed by holding the battery at 60°C for 24 hours. Here, "1C" refers to the magnitude of the current that changes the SOC from 0% to 100% in 1 hour.

[0065] <Measurement of reaction resistance value> After adjusting the SOC of the lithium ion secondary battery for evaluation according to each example prepared as described above to 50%, AC impedance measurement was performed at a measurement temperature of 25°C, a measurement frequency range of 0.01Hz to 100000Hz, and a current amplitude of 0.2C. The charge transfer resistance (Rct) calculated by equivalent circuit fitting of the Cole-Cole plot was taken as the reaction resistance. Here, Table 1 shows the relative values ​​(reaction resistance ratios) when the reaction resistance ratio of Example 1 is taken as 1.

[0066] [Table 1]

[0067] As shown in Table 1, in Examples 1 and 2 in which a metal film made of a metal species having a laser absorptance at wavelengths of 1 μm or more higher than copper was formed at the end of the copper foil, it was confirmed that the laser processability was improved compared to Example 3 in which no metal film was formed and Example 4 in which a metal film made of a metal species having a laser absorptance at wavelengths of 1 μm or more lower than copper was formed at the end of the copper foil. In addition, it was found that the battery resistance (reaction resistance ratio) increased in Example 5 compared to Example 1. The reason for the increase in the battery resistance in this way is considered to be as follows, although it is not intended to be particularly limited. That is, when a metal film is formed on the entire surface of the copper foil as in Example 5, a metal film is also formed in the region in contact with the negative electrode active material layer. And, it can be considered that a metal having a laser absorptance higher than copper at wavelengths of 1 μm or more has a lower electrical conductivity than copper, and therefore the battery resistance increased.

[0068] The specific examples of the technology disclosed herein have been described above. However, the above description is merely an example and does not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples exemplified in the above description. [Explanation of symbols]

[0069] 20 Electrode group 20a, 20b, 20c electrode body 22 Positive electrode 22a Cathode active material layer 22c Positive electrode current collector 24 Negative electrode 24a Negative electrode active material layer 24c Negative electrode current collector 27 Metal Film 100 batteries

Claims

1. a negative electrode current collector made of copper; a negative electrode active material layer formed on the negative electrode current collector; A negative electrode comprising: A tab is present on a portion of the periphery of the negative electrode current collector, A metal film made of at least one material selected from the group consisting of aluminum and molybdenum is formed on at least one surface of the tab.

2. The negative electrode according to claim 1 , wherein the metal film is formed on both sides of the tab.

3. A copper foil for a negative electrode current collector used to form a negative electrode active material layer in a predetermined region to construct a negative electrode, comprising: a metal film made of a metal species having a higher laser absorptivity than copper for a wavelength of 1 μm or more is formed on a part of a peripheral edge of at least one surface of the copper foil for a negative electrode current collector; The copper foil for a negative electrode current collector, wherein the metal film is formed so as not to overlap a region where the negative electrode active material layer is formed or so as to overlap only a part of the region.

4. A copper foil for a negative electrode current collector used to form a negative electrode active material layer in a predetermined region to construct a negative electrode, comprising: A metal film made of a metal species having a higher laser absorptivity at wavelengths of 1 μm or more than copper is formed only on the periphery of one or both sides of the copper foil for a negative electrode current collector.

5. 5. The copper foil for a negative electrode current collector according to claim 3, wherein the metal film is made of at least one material selected from the group consisting of aluminum, nickel, and molybdenum.

6. 5. The copper foil for a negative electrode current collector according to claim 3, wherein the metal film has a width of 5 mm or more.

7. The metal film, in a cross-sectional view of the copper foil for a negative electrode current collector, The copper foil for a negative electrode current collector according to claim 3 or 4, which is formed in a convex shape so that a ratio (S / T) of a thickness S of the metal film to a thickness T of the copper foil for a negative electrode current collector is 0.05 to 0.

3.

8. 5. The copper foil for a negative electrode current collector according to claim 3, wherein the portion on which the metal film is formed is used for forming a tab.

9. A method for manufacturing a copper foil for a negative electrode current collector used to construct a negative electrode by forming a negative electrode active material layer in a predetermined region, comprising the following steps: providing a copper foil; and a forming step of forming a metal film made of a metal species having a laser absorptivity of 1 μm or more higher than that of copper on a part of the periphery of at least one surface of the copper foil, wherein the metal film is formed so as not to overlap a region where the negative electrode active material layer is to be formed or to overlap only a part of the region; The method for producing a copper foil for a negative electrode current collector includes the steps of:

10. A method for producing a copper foil for a negative electrode current collector, which is used to form a negative electrode active material layer in a predetermined region to construct a negative electrode, comprising the steps of: providing a copper foil; and a forming step of forming a metal film made of a metal species having a higher laser absorptivity at wavelengths of 1 μm or more than copper only on the periphery of one or both sides of the copper foil; The method for producing a copper foil for a negative electrode current collector includes the steps of:

11. A battery comprising the negative electrode according to claim 1 or 2.

12. A method for producing a negative electrode by forming a negative electrode active material layer on a predetermined region of a copper foil for a negative electrode current collector, comprising the following steps: Providing a copper foil; and forming a metal film made of a metal species having a higher laser absorptance at wavelengths of 1 μm or more than copper on a part of the periphery of at least one surface of the copper foil; forming a negative electrode tab on a part of the periphery including the part on which the metal film is formed, wherein the negative electrode tab is formed by irradiating a laser having a wavelength of 1 μm or more; A method for producing a negative electrode comprising the steps of:

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