Lithium secondary battery

Abstract

Provided is a lithium secondary battery provided with: a laminate in which a plurality of positive electrodes and negative electrodes are laminated in a lamination direction via a separator, one of the positive electrodes and the negative electrodes including a first current collector configured by sandwiching a resin layer between a pair of conductive layers, the first current collector having a first end portion extending in a first direction different from the lamination direction; a first electrode tab electrically connected to the first end portion, the first electrode tab including: a first bonding trace formed by bonding with the first end portion; and a first insulating part which is arranged at an interval in the first direction from the first bonding trace and is covered with an insulating material. And a sealed container provided with a sealing part, the sealed container being configured such that, while sealing the laminated body inside the sealing part, the first insulating part of the first electrode tab is sandwiched in the sealing part, and a part of the first electrode tab is taken out to the outside of the sealed container.

Description

TECHNICAL FIELD

[0001] An exemplary embodiment of the present disclosure relates to a lithium secondary battery. BACKGROUND

[0002] Patent Literature 1 discloses improving the safety of a battery cell by using a current collector in which metal layers are formed on both surfaces of a resin film. The film surfaces / back surfaces of the resin film are separated by an insulating resin layer, and thus electric conduction cannot be performed. Therefore, when connecting electrode tabs for leading out wiring and electrode films, the surfaces / back surfaces of the electrodes, and the plurality of electrodes and the electrode tabs cannot be conducted. In this regard, Patent Literature 2 discloses folding and stacking the current collector multiple times on each metal layer in order to connect each metal layer separated by a resin layer and an electrode tab for leading out wiring.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 11-102711

[0006] Patent Literature 2: Japanese Patent Application Laid-Open No. 2013-016321 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] The present disclosure provides a technology for suppressing reduction in output characteristics and production capacity of a lithium secondary battery.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] In one exemplary embodiment of the present disclosure, a lithium secondary battery is provided, the lithium secondary battery including: a laminate obtained by laminating a positive electrode and a negative electrode in a lamination direction by a separator, one of the positive electrode and the negative electrode including a first current collector including a resin layer interposed between a pair of conductive layers, the first current collector including a first end portion extending in a first direction different from the lamination direction; a first electrode tab electrically connected to the first end portion, the first electrode tab including: a first joint trace formed by joining the first end portion; and a first insulating portion disposed apart from the first joint trace in the first direction by a gap and covered with an insulating material; and a sealed container including a sealing portion, the sealed container configured to, while the laminate is enclosed inside the sealing portion, sandwich the first insulating portion of the first electrode tab with the sealing portion and to extract a portion of the first electrode tab to an outside of the sealed container.

[0011] EFFECT OF THE INVENTION

[0012] According to one exemplary embodiment of the present disclosure, a technology for suppressing reduction in output characteristics and production capacity of a lithium secondary battery can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a plan view for explaining a configuration example of the secondary battery 1 .

[0014] Figure 2 It is an exploded perspective view for explaining a configuration example of the stacked body ST.

[0015] Figure 3 It is a perspective view showing an example of the negative electrode 10 .

[0016] Figure 4 It is a perspective view showing an example of the positive electrode 30 .

[0017] Figure 5 It is a diagram for explaining the joined state of the negative electrode tab 40 , the negative terminal P, and the metal piece M1 .

[0018] Figure 6 It is a diagram showing a cross section of the first joining mark W1.

[0019] Figure 7 This is a flowchart showing an example of the present production method.

[0020] Figure 8A It is a diagram for explaining step ST1.

[0021] Figure 8B It is a diagram for explaining step ST1.

[0022] Figure 9A It is a diagram for explaining step ST2.

[0023] Figure 9B It is a diagram for explaining step ST2.

[0024] Figure 9C It is a diagram for explaining step ST2.

[0025] Figure 9D It is a diagram for explaining step ST2.

[0026] Figure 10 It is a diagram for explaining step ST3.

[0027] Figure 11A It is a perspective view showing another example of the negative electrode 10 .

[0028] Figure 11B It is a perspective view showing another example of the negative electrode 10 .

[0029] Figure 11C It is a perspective view showing another example of the negative electrode 10 .

[0030] Figure 12is a perspective view showing another example of the positive electrode 30.

[0031] Figure 13 is a perspective view for explaining another stacked example of the negative electrode 10.

[0032] Figure 14 is a perspective view for explaining another stacked example of the negative electrode 10.

[0033] Figure 15 is a graph showing the results of Experiment 1.

[0034] Figure 16A is an example of a case where metal material overflowed in Experiment 1.

[0035] Figure 16B is an example of a case where metal material did not overflow in Experiment 1.

[0036] Figure 17 is a graph showing the results of Experiment 2. DETAILED DESCRIPTION

[0037] Hereinafter, each embodiment of the present disclosure will be described.

[0038] In one example embodiment, a lithium secondary battery is provided, the lithium secondary battery including: a laminate obtained by laminating a plurality of positive electrodes and negative electrodes in a lamination direction via separators, one of the positive electrodes and the negative electrodes including a first current collector composed of a pair of conductive layers sandwiching a resin layer, the first current collector including a first end portion extending in a first direction different from the lamination direction; a first electrode tab electrically connected to the first end portion, the first electrode tab including: a first joint trace formed by joining the first end portion; and a first insulating portion disposed apart from the first joint trace in the first direction by a distance and covered with an insulating material; and a sealed container including a sealed portion, the sealed container configured to, while enclosing the laminate inside the sealed portion, sandwich the first insulating portion of the first electrode tab in the sealed portion and extract a portion of the first electrode tab to an outside of the sealed container.

[0039] In one example embodiment, the first joint trace in the first end portion is disposed inside by 2 mm or more from an outer edge of the first end portion in the first direction.

[0040] In one example embodiment, the first joint trace in the first end portion is disposed inside by 2.5 mm or more from an outer edge of the first end portion in the first direction.

[0041] In one example embodiment, when the total number of the first current collectors included in the laminate is set to X and the distance between the first joint trace in the first end portion and the outer edge of the first end portion in the first direction is set to Y, the relationship Y > 0.048X + 1.3 is satisfied.

[0042] In one example embodiment, X is 10 or more.

[0043] In one example embodiment, the first joint trace is a welding trace.

[0044] In one example embodiment, the first joint trace includes, in a cross section in the stacking direction, a region in which a pair of conductive layers are integrated with each other.

[0045] In one example embodiment, the first end portion and the first electrode tab are joined to each other via the metal sheet.

[0046] In one example embodiment, the first joint trace is a welding trace.

[0047] In one example embodiment, the first joint trace includes, in a cross section in the stacking direction, a region in which a pair of conductive layers and the metal sheet are integrated.

[0048] In one example embodiment, the first end portion has a pre-joint trace formed by being joined to the metal sheet, the pre-joint trace being disposed at a position different from the first joint trace as viewed in the stacking direction.

[0049] In one example embodiment, the first current collector is a negative electrode current collector of a negative electrode, and the first electrode tab is a negative electrode tab connected to the negative electrode current collector.

[0050] In one example embodiment, the sealed container is composed of an aluminum laminate film.

[0051] In one example embodiment, the other of the positive electrode and the negative electrode includes a second current collector composed of a pair of conductive layers sandwiching a resin layer, the second current collector having a second end portion extending in a second direction different from the stacking direction.

[0052] In one example embodiment, a second electrode tab is further provided that is electrically connected to the second end portion of the second current collector, the second electrode tab including a second joint trace formed by being joined to the second end portion, and a second insulating portion disposed apart from the second joint trace in the second direction and covered with an insulating material, the sealed container being configured to sandwich the second insulating portion of the second electrode tab with the sealing portion and to take a portion of the second electrode tab to the outside of the sealed container.

[0053] In one example embodiment, the first direction and the second direction are the same direction.

[0054] In one example embodiment, the first direction and the second direction are different directions.

[0055] Hereinafter, each embodiment of the present disclosure will be described in detail with reference to the drawings. Further, in each drawing, the same or similar elements are denoted by the same reference signs, and overlapping description will be omitted. Unless otherwise specified, the positional relationship of up, down, left, right, and the like is described based on the positional relationship shown in the drawing. The dimensional ratio of the drawing does not represent the actual ratio, and the actual ratio is not limited to the ratio shown in the drawing.

[0056] As described above, in Patent Literature 2, the current collector is folded and stacked on each metal layer multiple times in order to connect each metal layer through the resin layer to the electrode tab for leading out the wiring. However, in this method, a new device mechanism is required to stack each metal layer while folding back the end portion of the current collector. In addition, the end portion of the current collector needs to be folded back in conjunction with the stacking, and the production capacity significantly deteriorates. In addition, in this method, even if the electrode tab can be mechanically joined with the current collector and each metal layer, the resistance of the joint portion increases, and the output characteristics decrease. In the lithium secondary battery 1 of one embodiment (hereinafter, also referred to as "secondary battery 1"), such problems can be solved.

[0057] <Configuration example of secondary battery>

[0058] Figure 1 is a plan view for explaining a configuration example of the secondary battery 1. As shown in Figure 1 , the secondary battery 1 is configured in a manner including a sealed container 100, a stacked body ST, a negative electrode tab 40, and a positive electrode tab 42. The stacked body ST is configured by stacking a plurality of positive electrodes and negative electrodes in a stacking direction (z direction) via a separator. Figure 1

[0059] The sealed container 100 includes a sealing portion 102 and a housing portion 104. The sealing portion 102 is provided along the entire outer periphery of the sealed container 100 to isolate the housing portion 104 from the outside of the sealed container 100.

[0060] The sealed container 100 is configured to take out the other end portion 40C of the negative electrode tab 40 to the outside of the sealed container 100 while the sealing portion 102 holds the insulating portion 40B of the negative electrode tab 40. Similarly, the sealed container 100 is configured to take out the other end portion 42C of the positive electrode tab 42 to the outside of the sealed container 100 while the sealing portion 102 holds the insulating portion 42B of the positive electrode tab 42.

[0061] The housing portion 104 of the sealed container 100 provides a sealed space for housing the stacked body ST. In one embodiment, the sealed container 100 can be configured by overlapping a pair of sealing members with each other and joining them along the entire outer periphery. The sealing member can be configured by multiple layers, for example, can be an aluminum laminate film.

[0062] ​The negative electrode tab 40 is electrically connected to the negative electrode end portion P of each negative electrode of the stack ST. In one embodiment, the negative electrode tab 40 is a strip-shaped body extending in a first direction (in the example shown in FIG. 1, the x direction) different from the stacking direction of the stack ST. Figure 1 The negative electrode tab 40 can have one end portion 40A, an insulating portion 40B, and another end portion 40C in the first direction. The one end portion 40A is joined to the negative electrode end portion P of each negative electrode of the stack ST, and a first joint mark Wl is formed by the joining. The first joint mark Wl can be one or a plurality of spots, or alternatively, a continuous line or surface.

[0063] The insulating portion 40B is covered with an insulating material IL such as a sealing film. The insulating portion 40B is disposed at a distance of a predetermined distance or more from the first joint mark Wl in the first direction. The other end portion 40C extends from the insulating portion 40B in the first direction, and is disposed outside the sealed container 100. The other end portion 40C can be connected to an external circuit.

[0064] The insulating portion 40B is covered with an insulating material IL such as a sealing film. The insulating portion 40B is disposed at a distance of a predetermined distance or more from the first joint mark Wl in the first direction. The other end portion 40C extends from the insulating portion 40B in the first direction, and is disposed outside the sealed container 100. The other end portion 40C can be connected to an external circuit.

[0065] In one embodiment, the negative electrode tab 40 can be composed of at least one selected from the group consisting of Cu, Ni, Ti, Fe, and other metals that do not react with Li, alloys thereof, and stainless steel (SUS).

[0066] The positive electrode tab 42 is electrically connected to the positive electrode end portion Q of each positive electrode of the stack ST. In one embodiment, the positive electrode tab 42 is a strip-shaped body extending in a second direction (in the example shown in FIG. 1, the x direction, which is the same as the first direction, but is not limited thereto, and can be a direction different from the first direction, for example, a direction opposite to the first direction) different from the stacking direction of the stack ST. The positive electrode tab 42 can have one end portion 42A, an insulating portion 42B, and another end portion 42C in the second direction. Figure 1 The one end portion 42A is joined to the positive electrode end portion Q of each positive electrode of the stack ST, and a second joint mark W2 is formed by the joining. The second joint mark W2 can be one or a plurality of spots, or alternatively, a continuous line or surface.

[0067] The insulating portion 42B is covered with an insulating material IL such as a sealing film. The insulating portion 42B is disposed at a distance of a predetermined distance or more from the second joint mark W2 in the second direction. The other end portion 42C extends from the insulating portion 42B in the first direction, and is disposed outside the sealed container 100. The other end portion 42C can be connected to an external circuit.

[0068] The insulating portion 42B is covered with an insulating material IL such as a sealing film. The insulating portion 42B is disposed at a distance of a predetermined distance or more from the first joint mark Wl in the first direction. The other end portion 40C extends from the insulating portion 40B in the first direction, and is disposed outside the sealed container 100. The other end portion 40C can be connected to an external circuit.

[0069] In one embodiment, the positive electrode tab 42 can be composed of at least one material selected from the group consisting of aluminum, titanium, stainless steel, nickel, and alloys thereof.

[0070] The stack ST is disposed in the sealed space of the housing portion 104. In one embodiment, the stack ST can be disposed in the sealed container 100 together with an electrolytic solution. The electrolytic solution is a liquid containing a solvent and an electrolyte, and functions as a conductive path for lithium ions. In addition, the electrolytic solution can be impregnated in the separators of the stack ST, and can also constitute a polymer electrolyte or a gel electrolyte by being held in a polymer.

[0071] Hereinafter, the stack ST will be described with reference to Figures 2-6 FIG. 6. Figure 2 As shown in FIG. 6, the stack ST is composed of a plurality of negative electrodes 10 and a plurality of positive electrodes 30 alternately stacked in the stacking direction (z direction) via the separators 20. As shown in FIG. 6, the plurality of negative electrodes 10 can each be composed of one sheet of flat sheet material. In addition, the plurality of positive electrodes 30 can each be composed of one sheet of flat sheet material. Furthermore, the plurality of negative electrodes 10 and / or the plurality of positive electrodes 30 can be composed of one sheet of flat sheet material folded or wound as a whole (for an example of such a scheme, see FIG. 7 and FIG. 8, which will be described later). Figure 2 Figure 2 Figure 2 Figure 13 Figure 14

[0072] In one embodiment, the number of layers of the positive electrodes and the negative electrodes in the stack ST can each be 5 or more, 10 or more, or 20 or more. In one embodiment, the number of layers of the positive electrodes and the negative electrodes in the stack ST can each be 50 or less, 40 or less, or 30 or less. The number of layers of the positive electrodes and the negative electrodes in the stack ST can be appropriately set in accordance with the energy density and the rated capacity of the secondary battery 1. Here, the energy density of the secondary battery 1 can be, for example, 300 Wh / kg or more. In addition, the rated capacity of the secondary battery 1 can be, for example, 1.5 Ah or more, and can also be 5 Ah or more.

[0073] Figure 2 ​​​​​​As shown, the negative electrode tab 40 is arranged in a manner that is aligned with the negative terminal portion P of each negative electrode 10 in the stacking direction. For example, the negative electrode tab 40 can be arranged above or below the negative terminal portion P in the stacking direction. In addition, for example, the negative electrode tab 40 can be arranged between a certain negative terminal portion P and the negative terminal portion P adjacent thereto. Similarly, the positive electrode tab 42 is arranged in a manner that is aligned with the positive terminal portion Q of each positive electrode 30 in the stacking direction. For example, the positive electrode tab 42 can be arranged above or below the positive terminal portion Q in the stacking direction. In addition, for example, the positive electrode tab 42 can be arranged between a certain positive terminal portion Q and the positive terminal portion Q adjacent thereto.

[0074] like Figure 2 As shown, the separator 20 is disposed between the negative electrode 10 and the positive electrode 30 in the stacking direction. The separator 20 physically and / or electrically isolates the negative electrode 10 from the positive electrode 30 and ensures ion conductivity of lithium ions. In one embodiment, the separator 20 may be at least one member selected from the group consisting of an insulating porous member, a polymer electrolyte, a gel electrolyte, and an inorganic solid electrolyte. The separator 20 may be a single member or a combination of two or more members.

[0075] (Negative electrode 10)

[0076] Figure 3 1 is a perspective view showing an example of the negative electrode 10. In one embodiment, the negative electrode 10 is configured to include a negative electrode current collector 12 and a negative electrode active material layer 14 disposed on the negative electrode current collector 12.

[0077] The negative electrode current collector 12 can be composed of a negative electrode insulating layer 120 and a pair of negative electrode conductive layers 122 disposed so as to sandwich the negative electrode insulating layer 120 .

[0078] In one embodiment, the negative electrode insulating layer 120 may be composed of, for example, a sheet-like (film-like) or fibrous resin. The resin may be, for example, at least one of polyolefin resins such as polyethylene terephthalate (PET), polyethylene, and polypropylene, and thermoplastic resins such as polystyrene, polyvinyl chloride, or polyamide. The negative electrode insulating layer 120 may be composed of a plurality of layers stacked at least one of the resins. In one embodiment, the negative electrode insulating layer 120 is formed of a material having a melting point of 150° C. to 300° C. In one embodiment, the thickness of the negative electrode insulating layer 120 may be 3 μm to 10 μm or more, or 4 μm to 8 μm or less. By including the negative electrode insulating layer 120 in the negative electrode current collector 12, the negative electrode 10 can be made lighter and its rigidity (thickness) can be increased.

[0079] The negative electrode conductive layer 122 is formed on both surfaces of the negative electrode insulating layer 120, sandwiching the negative electrode conductive layer 120. The negative electrode conductive layer 122 is in physical and / or electrical contact with the negative electrode active material layer 14, functioning by donating and accepting electrons from the negative electrode active material layer 14. In one embodiment, the negative electrode conductive layer 122 is formed of at least one selected from the group consisting of Cu, Ni, Ti, Fe, metals that do not react with lithium, their alloys, and stainless steel. Here, "metals that do not react with lithium" refers to metals that do not react with lithium ions or lithium metal to form alloys during the operation of the secondary battery 1. In one example, the negative electrode conductive layer 122 is Cu. In one embodiment, the negative electrode conductive layer 122 is formed by evaporation, sputtering, electrolytic plating, or lamination of the above materials onto the surfaces of both sides of the negative electrode insulating layer 120. In one embodiment, the thickness of the negative electrode conductive layer 122 may be 0.5 μm to 5 μm, 0.7 μm to 3 μm, or 0.8 μm to 2.0 μm.

[0080] The negative electrode active material layer 14 may be arranged on both sides of the negative electrode current collector 12, or may be arranged on only one side of the negative electrode current collector 12. The negative electrode active material layer 14 includes a negative electrode active material that generates electrode reactions, i.e., oxidation reactions and reduction reactions, at the negative electrode. The negative electrode active material may be, for example, lithium metal and alloys including lithium metal, carbon-based materials, metal oxides, metals alloyed with lithium, and alloys including such metals. The above-mentioned carbon-based materials may be, for example, graphene, graphite, hard carbon, carbon nanotubes, etc. The above-mentioned metal oxides may be, for example, titanium oxide compounds, cobalt oxide compounds, etc. The above-mentioned metals alloyed with lithium may be, for example, silicon, silicon oxide, germanium, tin, lead, aluminum, gallium, and materials pre-doped with lithium.

[0081] like Figure 3 As shown, the negative electrode current collector 12 has a negative terminal P. In one embodiment, the negative terminal P is a portion of the negative electrode current collector 12 extending from the side of the negative electrode current collector 12 along a first direction ( Figure 3 The negative electrode active material layer 14 may not be arranged on the negative terminal P.

[0082] In one embodiment, a metal sheet M1 for the negative electrode may be provided on the negative terminal P. Figure 3As shown, the metal sheet M1 can be bonded to one side of the negative terminal P, or can be bonded to both sides of the negative terminal P. The metal sheet M1 can be provided only at the negative terminal P of a portion of the negative electrode 10, or can be provided at the negative terminal P of all the negative electrodes 10. The metal sheet M1 can be made of the same material as the negative electrode conductive layer 122, which is Cu in one example. In one embodiment, the thickness of the metal sheet M1 can be greater than 3 μm, greater than 5 μm, or greater than 7 μm. In one embodiment, the thickness of the metal sheet M1 can be less than 15 μm, less than 12 μm, or less than 10 μm.

[0083] like Figure 3 As shown, a first joining mark W1 is formed on the metal sheet M1 and the negative terminal P by joining with the negative electrode tab 40. In addition, in one embodiment, a pre-joining mark WP1 formed by joining the metal sheet M1 and the negative terminal P can be formed. The pre-joining mark WP1 is a joining mark formed when the metal sheet M1 and the negative terminal P are first joined before joining with the negative electrode tab 40 (hereinafter also referred to as "pre-joining"). The first joining mark W1 and the pre-joining mark WP1 can be formed at positions different from each other when viewed from the stacking direction (z direction). The pre-joining mark WP1 can be formed in one or more columns in a linear manner along the negative terminal P, or can be formed in a plurality of points. In addition, when pre-joining is not performed but the metal sheet M1, the negative terminal P and the negative electrode tab 40 are joined at one time, only the first joining mark W1 is formed, and the pre-joining mark WP1 is not formed.

[0084] In one embodiment, the first joining mark W1 and / or the pre-joining mark WP1 may be a joining mark formed by welding, i.e., a weld mark. Welding may be, for example, ultrasonic welding, laser welding, resistance welding, or spot welding. In one example, the welding is ultrasonic welding. In one embodiment, the metal sheet M1 and the negative conductive layer 122 of the negative terminal P may be partially or completely fused together in the first joining mark W1 and / or the pre-joining mark WP1 by heat or the like.

[0085] (Positive electrode 30)

[0086] Figure 4 3 is a perspective view showing an example of the positive electrode 30. In one embodiment, the positive electrode 30 is configured to include a positive electrode current collector 32 and a positive electrode active material layer 34 disposed on the positive electrode current collector 32.

[0087] The positive electrode current collector 32 can be composed of a positive electrode insulating layer 320 and a pair of positive electrode conductive layers 322 arranged so as to sandwich the positive electrode insulating layer 320 .

[0088] The positive electrode insulating layer 320 can be formed of a sheet (film) or a fibrous resin, for example. The resin can be at least one of polyethylene terephthalate (PET), polyethylene, polypropylene or other polyolefin resin, polystyrene, polyvinyl chloride, or a thermoplastic resin such as polyamide, for example. The positive electrode insulating layer 320 can be formed of at least one of the resins in multiple layers. In one embodiment, the positive electrode insulating layer 320 is formed of a material having a melting point of 150°C or higher and 300°C or lower. In one embodiment, the thickness of the positive electrode insulating layer 320 can be 3 μm or more and 10 μm or less, or 4 μm or more and 8 μm or less.

[0089] The positive electrode insulating layer 320 can function in such a way as to melt in the event of abnormal heat generation in an overcharged state or a high-temperature state, for example, to break the positive electrode 30 and block a short-circuit current inside the battery. Thus, the temperature inside the laminate ST can be prevented from rising sharply, and the battery can be prevented from catching fire during use of the secondary battery 1. That is, the positive electrode insulating layer 320 can contribute to improved safety of the secondary battery 1.

[0090] The positive electrode conductive layer 322 is formed on both surfaces of the positive electrode insulating layer 320 in such a way as to sandwich the positive electrode insulating layer 320. The positive electrode conductive layer 322 is in physical and / or electrical contact with the positive electrode active material layer 34 to function in such a way as to accept and release electrons from and to the positive electrode active material layer 34. The positive electrode conductive layer 322 is formed of a conductive body that does not react with lithium ions in the secondary battery 1. In one embodiment, the positive electrode conductive layer 322 is formed of at least one material selected from the group consisting of aluminum, titanium, stainless steel, nickel, and alloys thereof. In one example, the positive electrode conductive layer 322 is aluminum or an aluminum alloy. In one embodiment, the positive electrode conductive layer 322 is formed by vapor deposition, sputtering, electrolytic plating, or adhesion of the above-described material on the surfaces of both sides of the positive electrode insulating layer 320. In one embodiment, the thickness of the positive electrode conductive layer 322 can be 0.5 μm or more and 5 μm or less, 0.7 μm or more and 3 μm or less, or 0.8 μm or more and 2.0 μm or less.

[0091] The positive electrode active material layer 34 can include a positive electrode active material for holding lithium ions, which are filled into and released from the positive electrode active material by charging and discharging of the battery. The positive electrode active material can be a metal oxide or a metal phosphate. The metal oxide can be a cobalt oxide-based compound, a manganese oxide-based compound, or a nickel oxide-based compound, for example. The metal phosphate can be an iron phosphate-based compound or a cobalt phosphate-based compound, for example. In one embodiment, the positive electrode active material can be at least one selected from LiCoO2, LiNi x Co y Mn z O (x + y + z = 1), LiNi x Co y Al zO(x+y+z=1), LiNi x Mn y At least one of the group consisting of O(x+y=1), LiNiO2, LiMn2O4, LiFePO4, LiCoPO4, LiFeOF, LiNiOF, and LiTiS2. The positive electrode active material can be used alone or in combination of two or more. In one embodiment, the positive electrode active material layer 34 may include components other than the positive electrode active material, such as one or more sacrificial positive electrode materials, a gel electrolyte, a polymer electrolyte, a conductive additive, and / or a binder.

[0092] like Figure 4 As shown, the positive electrode current collector 32 has a positive terminal Q. In one embodiment, the positive terminal Q is a portion of the positive electrode current collector 32 extending from the side of the positive electrode current collector 32 in a second direction different from the stacking direction (in the direction of the stacking direction). Figure 4 In the example shown, the positive electrode active material layer 34 is not arranged on the positive terminal Q.

[0093] In one embodiment, a metal sheet M2 for the positive electrode may be provided on the positive terminal Q. Figure 4 As shown, the metal sheet M2 can be bonded to one side of the positive terminal Q, or can be bonded to both sides of the positive terminal Q. In addition, the metal sheet M2 can be provided only at the positive terminal Q of a portion of the positive electrode 30, or can be provided at the positive terminal Q of all the positive electrodes 30. In one embodiment, the metal sheet M2 is made of the same material as the positive electrode conductive layer 322. In one example, the metal sheet M2 is aluminum or an aluminum alloy. In one example, the metal sheet M2 can be a hard aluminum foil or a soft aluminum foil. The soft aluminum foil can be formed by subjecting the hard aluminum foil to a high-temperature (about 400°C) heat treatment. In one embodiment, the thickness of the metal sheet M2 can be greater than 3 μm, greater than 5 μm, or greater than 7 μm. In one embodiment, the thickness of the metal sheet M2 can be less than 15 μm, less than 12 μm, or less than 10 μm.

[0094] like Figure 4As shown, a second joining mark W2 is formed on the metal sheet M2 and the positive terminal Q by joining with the positive electrode tab 42. In addition, in one embodiment, a pre-joining mark WP2 formed by joining the metal sheet M2 and the positive terminal Q can be formed. The pre-joining mark WP2 is a joining mark formed when the metal sheet M2 and the positive terminal Q are joined before joining with the positive electrode tab 42. The second joining mark W2 and the pre-joining mark WP2 can be formed at positions different from each other when viewed from the stacking direction (z direction). The pre-joining mark WP2 can be formed in one or more columns in a linear manner along the positive terminal Q, or it can be formed in a plurality of points. In addition, when pre-joining is not performed but the metal sheet M2, the positive terminal Q and the positive electrode tab 42 are joined at one time, only the second joining mark W2 is formed, and the pre-joining mark WP2 is not formed.

[0095] In one embodiment, the second joining mark W2 and / or the pre-joining mark WP2 may be a joining mark formed by welding, i.e., a weld mark. Welding may be, for example, ultrasonic welding, laser welding, resistance welding, or spot welding. In one example, the welding is ultrasonic welding. In one embodiment, the metal sheet M2 and the positive conductive layer 322 of the positive terminal Q may be partially or completely fused together in the second joining mark W2 and / or the pre-joining mark WP2 by heat or the like.

[0096] (First bonding mark W1 and preliminary bonding mark WP1)

[0097] Figure 5 It is a diagram for explaining the joined state of the negative electrode tab 40 , the negative terminal P, and the metal piece M1 . Figure 5 A cross section of the negative terminal P including the first joining mark W1 and the preliminary joining mark WP1 is schematically shown along the xz plane.

[0098] like Figure 5 As shown, the first joint mark W1 and the pre-joint mark WP1 are located at different positions when viewed in the stacking direction. The first joint mark W1 is formed throughout the entire negative electrode tab 40, each negative terminal P, and each metal sheet M1. That is, the first joint mark W1 is formed from the negative electrode tab 40 along the stacking direction all the way to the bottommost negative terminal P. In contrast, the pre-joint mark WP1 is formed for each negative terminal P. In other words, a single pre-joint mark WP1 does not span multiple negative terminals P.

[0099] like Figure 5As shown, at the negative terminal P, the first joining mark W1 is arranged on the inner side of the outer edge of the first direction of the negative terminal P by a predetermined distance Y or more. In one embodiment, the distance Y can be 2.0 mm, 2.5 mm, or 3.0 mm. In one embodiment, when the number of stacked layers of the negative electrodes 10 in the stacked body ST (i.e., the total number of negative terminals P) is set to X, the predetermined distance Y can be set to a relationship of Y>0.048X+1.3. In one embodiment, X can be greater than 10, greater than 15, or greater than 20.

[0100] Figure 6 It is a diagram showing a cross section of the first joining mark W1. Figure 6 The cross section ( Figure 5 AA section). Figure 6 As shown, the cross section of the first joint mark W1 includes a first region R1 and a second region R2. In one embodiment, the cross section of the first joint mark W1 may have a concave portion that is concave in one direction of the stacking direction.

[0101] In the first region R1, the negative conductive layer 122 and the metal sheet M1 are integrated and laminated, and are bonded to the negative electrode tab 40. Here, integration and lamination include a state where the negative conductive layer 122 and the metal sheet M1 are partially or entirely fused by heat or the like (a state where the layers are indistinguishable).

[0102] In one embodiment, the first region R1 may substantially not include the negative insulating layer 120 along the stacking direction. The first region R1 provides a physical path for electrically connecting the negative electrode tab 40 with each negative conductive layer 122 and the metal sheet M1.

[0103] In one embodiment, the first region R1 may be formed between two second regions R2. In one embodiment, the maximum thickness of the first region R1 may be less than half of the maximum thickness of the second region R2.

[0104] In the second region R2, a pair of negative conductive layers 122 and the metal sheet M1 are stacked with the negative insulating layer 120 interposed therebetween. That is, the second region R2 includes the negative insulating layer 120 in the stacking direction.

[0105] In one embodiment, the first bonding mark W1 is formed by pressing the negative electrode tab 40, the negative terminal P, and the metal sheet M1 in the stacking direction. At this time, heat can be applied to the pressing portion. For example, the first bonding mark W1 can be formed by welding (in this case, the first bonding mark W1 is a welding mark). As a result, the negative electrode insulating layer 120 softens at the pressing portion and is stretched from the pressing portion to the lateral direction ( Figure 6In addition, at the pressed portion, each negative electrode conductive layer 122 is thermally fused with the metal sheet M1 to form a single body. This allows the first region R1 and the second region R2 to be formed.

[0106] Here, when the first bonding trace W1 is formed, a portion of the metal material constituting the negative electrode conductive layer 122 and / or the metal sheet M1 is moved from the pressed portion to the first direction ( Figure 5 and Figure 6 At this time, if the metal material flies outward from the negative terminal P and reaches the insulating material IL of the insulating portion 40B of the negative electrode tab 40 (see Figure 1 、 Figure 5 ), then the sealing portion 102 (refer to Figure 1 ) may cause insulation failure. For example, if metal material flying out of the negative electrode terminal P is present in the insulating portion 40B, and cracks occur in the sealing portion 102 (e.g., the aluminum laminate film), a short circuit may occur between the negative electrode terminal P of the negative electrode 10 and the sealed container 100. In this case, damage to the sealing portion 102 may cause a decrease in the performance or life of the secondary battery 1.

[0107] In this regard, in the secondary battery 1, as described above, the first joint mark W1 is arranged at a predetermined distance Y or more inward from the outer edge of the negative terminal P. Therefore, even if a portion of the metal material is squeezed out from the pressing portion in the first direction when the first joint mark W1 is formed, the metal material is prevented from flying out toward the outer edge of the negative terminal P and reaching the insulating portion 40B of the negative electrode tab 40. As a result, the sealing portion 102 (see FIG. 1 ) between the negative electrode 10 and the sealed container 100 can be prevented from being damaged. Figure 1 ) is poorly insulated.

[0108] Furthermore, as described above, in one embodiment, a negative electrode metal sheet M1 may be provided on the negative terminal P. In this case, the metal sheet M1 functions as an additional conductive layer for the negative electrode conductive layer 122 in the first joint mark W1, increasing the proportion of the conductive layer relative to the negative electrode insulating layer 120. Therefore, it is possible to suppress the increase in resistance in the first joint mark W1 and improve the output characteristics of the secondary battery 1. Furthermore, when the total number of negative electrodes 10 (the number of stacked layers) is large, it is necessary to press the negative electrode tab 40 and each negative terminal P with greater force to achieve bonding. However, since the metal sheet M1 functions as a protective layer for the negative electrode conductive layer 122, it is possible to suppress damage or breakage of the negative electrode conductive layer 122. This can improve the production yield of the secondary battery 1. In one embodiment, the resistance of the first joint mark W1 can be 5.0 mΩ or less, 3.0 mΩ or less, 1.0 mΩ or less, or 0.5 mΩ or less.

[0109] (Second joining trace W2 and pre-joining trace WP2)

[0110] The second joining trace W2 and the pre-joining trace WP2 of the positive electrode tab 42, the positive electrode end portion Q, and the metal sheet M2 can be configured in the same manner as the first joining trace W1 and the pre-joining trace WP1 described in Figure 5 and Figure 6 For example, in one embodiment, the second joining trace W2 can be disposed on the inner side of a predetermined distance Y or more from the outer edge of the positive electrode end portion Q. Thereby, it is possible to suppress the insulation failure between the positive electrode 30 and the sealing portion 102 (refer to Figure 1 ) of the sealing container 100.

[0111] <Method of manufacturing secondary battery 1>

[0112] Next, an example of a method of manufacturing the secondary battery 1 (hereinafter, also referred to as "the present manufacturing method") will be described with reference to Figures 7-10 Figure 7 is a flowchart showing an example of the present manufacturing method. Figure 8A and Figure 8B are diagrams for explaining the process ST1 of Figure 7 Figures 9A-9D is a diagram for explaining the process ST2 of Figure 7 Figure 10 is a diagram for explaining the process ST3 of Figure 7

[0113] As shown in Figure 7 , the present manufacturing method can include the following processes: the process ST1 of preparing the negative electrode sheet S1; the process ST2 of joining the metal sheet M1; the process ST3 of cutting out a plurality of negative electrodes 10; the process S4 of preparing the positive electrode sheet S2; the process ST5 of joining the metal sheet M2; the process ST6 of cutting out a plurality of positive electrodes 30; the process ST7 of forming a laminate ST; the process ST8 of joining the electrode tab and the current collector; and the process ST9 of sealing the laminate ST in the sealing container 100.

[0114] First, in the process ST1, as shown in Figure 8A and Figure 8B , the negative electrode sheet S1 is prepared. Figure 8A is a plan view of the negative electrode sheet S1. Figure 8B is a B-B sectional view of Figure 8A As shown in Figure 8A , the negative electrode sheet S1 can be a sheet in a band shape having a long side direction (y direction) and a short side direction (x direction). In one embodiment, as shown in Figure 8A and Figure 8B ​​​​As shown, the negative electrode sheet S1 can be composed of a negative electrode collector 12 and a negative electrode active material layer 14 coated on both sides of the negative electrode collector 12. The negative electrode active material layer 14 is not formed at one end of the negative electrode sheet S1 in the short side direction (x direction), and the negative electrode conductive layer 122 of the negative electrode collector 12 is exposed.

[0115] In one embodiment, the separator 20 may be initially provided on one side of the negative electrode active material layer 14 (the side not formed with the negative electrode conductive layer 122). In this case, the separator 20 does not need to be aligned between the negative electrode 10 and the positive electrode 30 in step ST7.

[0116] Next, in step ST2, as shown in FIG. Figures 9A-9D As shown, a metal sheet M1 is bonded to one end of the negative electrode sheet S1 in the short side direction. Figure 9A It is a plan view of the negative electrode sheet S1 joined to the metal sheet M1. Figures 9B-9D yes Figure 9A An example of CC cross section.

[0117] By joining in step ST2, as Figure 9A As shown, the pre-joining mark WP1 is formed in a linear shape along the longitudinal direction. The metal sheet M1 can be joined to the negative electrode sheet S1 by welding. Welding can be, for example, ultrasonic welding, laser welding, resistance welding, or spot welding. In one example, the welding is ultrasonic welding.

[0118] In one embodiment, the bonding in step ST2 can be performed by pressing the metal sheet M1 against the negative electrode current collector 12. For example, Figure 9B or Figure 9C As shown, the pre-joining mark WP1 may be formed in such a manner that the metal sheet M1 is recessed toward the negative electrode current collector 12. Figure 9B As shown, the pre-joint trace WP1 may be provided between the metal sheet M1 and one of the negative conductive layers 122 (with which the metal sheet M1 contacts). In this case, in the pre-joint trace WP1, the metal sheet M1 is not electrically connected to the other negative conductive layer 122. In one embodiment, as shown in FIG. Figure 9C As shown, the pre-joint trace WP1 may be provided between the metal sheet M1 and the two negative electrode conductive layers 122. In this case, the metal sheet M1 is electrically connected to the two negative electrode conductive layers 122 in the pre-joint trace WP1.

[0119] In one embodiment, the bonding in step ST2 can be performed by pressing the negative electrode current collector 12 against the metal sheet M1. Figure 9DAs shown, the pre-bonding trace WP1 can be formed in such a manner that the negative current collector 12 is recessed toward the metal sheet M1 side. In this case, in the pre-bonding trace WP1, the metal sheet M1 is electrically connected to the two negative conductive layers 122.

[0120] Next, in the process ST3, a plurality of negative electrodes 10 are cut out from the negative sheet S1. Specifically, as shown in FIG. 4B, a plurality of negative electrodes 10 of a given shape are cut out from the negative sheet S1 using a cutter or a laser, or the like. Thereby, a plurality of negative electrodes 10 to which the metal sheet M1 is pre-bonded are obtained. Figure 10 As shown, the pre-bonding trace WP1 can be formed in such a manner that the negative current collector 12 is recessed toward the metal sheet M1 side. In this case, in the pre-bonding trace WP1, the metal sheet M1 is electrically connected to the two negative conductive layers 122.

[0121] The processes ST4 to ST6 can be executed similarly to the processes ST1 to ST3. That is, the positive sheet S2 including the positive current collector 32 and the positive active material layer 34 can be prepared (process ST4), the metal sheet M2 is bonded at one end in the short side direction of the positive sheet S2 (process ST5), and a plurality of positive electrodes 30 are cut out from the metal sheet M2 (process ST6).

[0122] Next, in the process ST7, the stack ST is formed. Specifically, as shown in FIG. 5, the negative electrode 10 and the positive electrode 30 prepared in the processes ST1 and ST3 are alternately arranged with each other in the stacking direction via the separator 20. Figure 2 As shown, the pre-bonding trace WP1 can be formed in such a manner that the negative current collector 12 is recessed toward the metal sheet M1 side. In this case, in the pre-bonding trace WP1, the metal sheet M1 is electrically connected to the two negative conductive layers 122.

[0123] Next, in the process ST8, the electrode tabs and the current collectors are bonded. Specifically, the negative end portion P of the negative current collector 12 and the metal sheet M1 are bonded to the negative electrode tab 40 in such a manner that the above-described first bonding trace W1 is formed. At this time, the bonding site with the negative electrode tab 40 is located at a position inside the outer edge of the negative end portion P by a predetermined distance Y or more. Further, the bonding site can be a position at which the first bonding trace W1 does not coincide with the pre-bonding trace WP1 in the stacking direction. In addition, the positive end portion Q of the positive current collector 32 and the metal sheet M2 are bonded to the positive electrode tab 42 in such a manner that the above-described second bonding trace W2 is formed. At this time, the bonding site with the positive electrode tab 42 is located at a position inside the outer edge of the positive end portion Q by a predetermined distance Y or more. Further, the bonding site can be a position at which the second bonding trace W2 does not coincide with the pre-bonding trace WP2 in the stacking direction. The bonding of the electrode tabs and the current collectors can be performed by ultrasonic welding, laser welding, resistance welding, or spot welding.

[0124] Next, in the process ST9, the stack ST formed in the process ST8 is enclosed in the sealing container 100. At this time, as shown in FIG. 6, the stack ST is enclosed in the sealing container 100 in such a manner that the stack ST is not in contact with the inner wall of the sealing container 100. Figure 1As shown, the insulating portion 40B of the negative electrode tab 40 is disposed in the sealed portion 102 of the sealed container 100, and the other end portion 40C of the negative electrode tab 40 is taken out to the outside of the sealed container 100. In addition, the insulating portion 42B of the positive electrode tab 42 is disposed in the sealed portion 102 of the sealed container 100, and the other end portion 42C of the positive electrode tab 42 is taken out to the outside of the sealed container 100. In one embodiment, an electrolyte can be enclosed in the sealed container 100 together with the laminate ST. By the above operation, the secondary battery 1 is manufactured.

[0125] In the present manufacturing method, in the process ST8, the joining site with the negative electrode tab 40 is located at a position inside a predetermined distance Y from the outer edge of the negative electrode end portion P. Thereby, the flying out of a part of the metal material constituting the negative electrode conductive layer 122 and / or the metal sheet Ml from the outer edge of the negative electrode end portion P to the insulating portion 40B of the negative electrode tab 40 is suppressed. Thereby, the insulating failure between the negative electrode 10 and the sealed portion 102 of the sealed container 100 can be suppressed. In the present manufacturing method, in the process ST8, the joining site with the positive electrode tab 42 is located at a position inside a predetermined distance Y from the outer edge of the positive electrode end portion Q, and thus the above points are also applicable to the positive electrode 30.

[0126] In addition, in the present manufacturing method, the metal sheet Ml is joined with the negative electrode sheet S1 in advance in the process ST2. Therefore, in the process ST3, the metal sheet Ml can be simultaneously cut in conformity with the shape of the negative electrode end portion P. That is, no other process is required to cut the metal sheet Ml in conformity with the shape of the negative electrode end portion P. In addition, in the process ST9, no alignment of the metal sheet Ml with the negative electrode end portion P is required, and thus the joining of the negative electrode tab 40 with the negative electrode end portion P becomes easy. Moreover, in the process ST9, the first joining trace Wl can be set to not overlap the pre-joining trace WP1 in the stacking direction in principle. By setting the first joining trace Wl to not overlap the pre-joining trace WP2 in the stacking direction, the joining state of the first joining trace Wl is improved compared to the case where they are set to overlap, and the increase in the resistance of the first joining trace Wl can be suppressed. In the present manufacturing method, the metal sheet M2 is joined with the positive electrode sheet S2 in advance in the process ST4, and thus the above points are also applicable to the positive electrode 30.

[0127] <Usage method of the secondary battery 1>

[0128] The secondary battery 1 is charged and discharged by connecting the negative electrode tab 40 to one end of an external circuit and connecting the positive electrode tab 42 to the other end of the external circuit. The external circuit can be, for example, a resistor, a power source, a device, a component, another battery, or a potentiostat. The negative electrode end portions P of the plurality of negative electrodes 10 can be connected to the external circuit at the same potential as each other. In addition, the positive electrode end portions Q of the plurality of positive electrodes 30 can be connected to the external circuit at the same potential as each other.

[0129] If a voltage that causes current to flow from the negative electrode tab 40 to the positive electrode tab 42 through the external circuit is applied between the negative electrode tab 40 and the positive electrode tab 42, the secondary battery 1 is charged, and lithium metal is deposited on the negative electrode 10. With respect to the charged secondary battery 1, if the negative electrode tab 40 and the positive electrode tab 42 are connected via a desired external circuit, the secondary battery 1 is discharged, and the lithium metal of the negative electrode 10 is electrolytically eluted.

[0130] In one embodiment, the secondary battery 1 can form a solid electrolyte interface layer (SEI layer) on the surface of the negative electrode 10 or the surface of the separator 20 (i.e., the interface between the negative electrode 10 and the separator 20) by the first charging (initial charging) after the assembly of the battery. The SEI layer can contain, for example, an inorganic compound including lithium or an organic compound including lithium. In one embodiment, the thickness of the SEI layer is 1.0 nm or more and 10 μm or less. In the case where the SEI layer is formed in the secondary battery 1, lithium metal is deposited or dissolved at the interface between the negative electrode 10 and / or the separator 20 and the SEI layer by charging and discharging.

[0131] According to the secondary battery 1 described above, the output characteristics of the battery and the production capacity can be improved.

[0132] <Variant>

[0133] The secondary battery 1 can be variously modified without departing from the scope and spirit of the present disclosure.

[0134] (Negative electrode 10)

[0135] Figures 11A-11C are perspective views showing other examples of the negative electrode 10. For example, as shown in Figs. 10A and 10B, a metal sheet can not be provided at the negative electrode end portion P of the negative electrode 10. Figure 11A Figure 11C

[0136] For example, as shown in Figs. 11A and 11B, a metal sheet can not be provided at the negative electrode end portion P of the negative electrode 10. Figure 11B Figure 11C ​​​As shown, the negative electrode 10 can be composed of the negative electrode current collector 12, and substantially have no negative electrode active material. Here, the negative electrode 10 "substantially have no negative electrode active material" includes, for example, a layer thickness of the negative electrode active material eluted from the negative electrode 10 at the end of discharge (for example, a state in which the open-circuit voltage of the battery is 2.5 V or more and 3.6 V or less) is 25 μm or less. Further, the layer thickness of the negative electrode active material at the end of discharge can be 20 μm or less, 15 μm or less, 10 μm or less, or 5 μm or less, or can be 0 μm. By the negative electrode 10 substantially having no negative electrode active material, in addition to the weight energy density being improved, the energy density per unit volume can also be improved. Further, in this case, the secondary battery 1 can also be referred to as an "anode-free lithium battery", a "zero anode lithium battery", or an "anode-less lithium battery".

[0137] In Figure 11B , Figure 11C the example shown, the negative electrode 10 has no negative electrode active material before the initial charging of the battery (a state from after the battery is assembled until the first charging is performed). That is, the secondary battery 1 can be charged and discharged by the lithium metal being eluted from the negative electrode after the initial charging, and the eluted lithium metal. In this case, the volume and mass occupied by the negative electrode active material are suppressed, the volume and mass of the entire battery are made small, and the energy density is high in principle. Further, "the lithium metal being eluted from the negative electrode" includes not only the lithium metal being eluted from the surface of the negative electrode, but also the lithium metal being eluted from the surface or inside of the solid electrolyte interface (SEI) layer, the surface or inside of the buffer function layer, or the like, which will be described later.

[0138] In Figure 11B , Figure 11C the example shown, in a case where the mass of the lithium metal eluted from the negative electrode in a state of 4.2 V is set as M 4.2 , and the mass of the lithium metal in a state of 3.0 V is set as M 3.0 , M 3.0 / M 4.2 of the negative electrode 10 can be 40% or less, or 35% or less. In one embodiment, M 3.0 / M 4.2 may be 1.0% or more, 2.0% or more, 3.0% or more, or 4.0% or more.

[0139] In Figure 11B , Figure 11CIn the illustrated example, the thickness of the negative electrode 10 can be 1.0 μm or more and 30 μm or less. Thereby, the volume occupied by the negative electrode 10 in the secondary battery 1 is reduced, and the energy density can be improved. The thickness of the negative electrode 10 can be 2.0 μm or more and 20 μm or less, 2.0 μm or more and 18 μm or less, or 3.0 μm or more and 15 μm or less.

[0140] (buffer function layer)

[0141] In one embodiment, a buffer function layer of a porous or fibrous shape can be provided between the negative electrode 10 and the separator 20. The buffer function layer has a solid portion (including a gel-like portion) having ion conductivity and electrical conductivity, and a void portion constituted by the gaps of the solid portion. In this case, lithium metal can be deposited on the surface of the negative electrode 10 (the interface between the negative electrode 10 and the buffer function layer) and / or inside the buffer function layer (the surface of the solid portion of the buffer function layer).

[0142] (positive electrode 30)

[0143] Figure 12 is a perspective view showing another example of the positive electrode 30. For example, as Figure 12 indicated, a metal sheet can not be provided at the positive electrode end portion Q of the positive electrode 30.

[0144] (laminate ST)

[0145] Figure 13 and Figure 14 are perspective views for explaining other laminated examples of the plurality of negative electrodes 10. As Figure 13 and Figure 14 indicated, the plurality of negative electrodes 10 can not each be a sheet of a flat shape, but can be constituted as a whole in the form of a sheet on a flat sheet. For example, as Figure 13 indicated, the plurality of negative electrodes 10 can be constituted by winding the negative electrode sheet S1 multiple times. In addition, for example, as Figure 14 indicated, the plurality of negative electrodes 10 can be constituted by alternately bending the negative electrode sheet S1 multiple times at an acute angle. Further, the negative electrode sheet S1 can be constituted in the manner as Figure 8A indicated, and in addition, the metal sheet M1 can be joined as Figure 9A indicated.

[0146] As for the plurality of positive electrodes 30 as well, it can not each be a sheet of a flat shape, but can be constituted as a whole in the form of a sheet on a flat sheet. For example, as with Figure 13 the plurality of positive electrodes 30 can be constituted by winding the positive electrode sheet S2 multiple times. In addition, for example, as with Figure 14 the plurality of positive electrodes 30 can be constituted by alternately bending the positive electrode sheet S2 multiple times at an acute angle.

[0147] The following describes experiments performed to verify the effects of the present disclosure. The present disclosure is not limited in any way by the following experiments.

[0148] <Experiment 1>

[0149] Figure 15 is a graph showing the results of Experiment 1. Figure 16A is an example of a case in which metal material overflowed in Experiment 1. Figure 16B is an example of a case in which metal material did not overflow in Experiment 1. Figure 16A and Figure 16B is an example of a case in which the electrode tab 40 is viewed from the negative electrode end portion P side (from the z-direction lowermost negative electrode end portion P, in terms of viewing the electrode tab 40). Figure 2

[0150] In Experiment 1, a plurality of laminates ST having the structure shown in Figure 2 were prepared. In each of the laminates ST, the number of laminated layers X of the negative electrode 10 (11 sheets or 21 sheets), the distance Y from the outer edge of the negative electrode end portion P to the first joint mark W1 (refer to Figure 5 , 0.5 mm to 4.45 mm), and the presence or absence of the metal sheet M1 were different. The general configuration of each of the laminates ST was as follows.

[0151] In each of the laminates ST, as the negative electrode insulating layer 120, a 6-μm-thick polyethylene terephthalate (PET) was used. As the negative electrode conductive layer 122, a 1.0-μm-thick copper foil was used. As the negative electrode active material layer 14, a mixed material obtained by mixing 97 parts by mass of graphite, 0.5 parts by mass of carbon black as a conductive aid, and 1.5 parts by mass of carboxymethyl cellulose (CMC) and 1.0 parts by mass of styrene-butadiene rubber (SBR) as binders in water as a solvent was used. As for the laminate in which the metal sheet M1 was disposed, a 4-μm-thick copper foil was used as the metal sheet M1. As the negative electrode electrode tab 40, a copper on which nickel plating was performed having a thickness of 0.2 mm was used.

[0152] In each of the laminates ST, as the separator 20, a sheet coated with a mixture of polyvinylidene fluoride (PVDF) and AI2O3 on the surface was used.

[0153] In each of the laminates ST, as the positive electrode insulating layer 320, a 6-μm-thick film-shaped polyethylene terephthalate was used. As the positive electrode conductive layer 322, a 1.0-μm-thick aluminum was used. As the positive electrode active material layer 34, a mixed material obtained by mixing 96 parts by mass of LiNi 0.8 Co 0.15 Al 0.05 ​O2, 2 parts by mass of carbon black as a conductive aid, and 2 parts by mass of polyvinylidene fluoride (PVDF) as a binder. In addition, as the metal sheet M2, aluminum was used. As the positive electrode tab 42, 0.2 mm-thick aluminum was used.

[0154] For each of the laminates ST prepared as above, whether or not there was "spillage" of the metal material from the negative electrode end portion P was evaluated. As shown in Figure 16A , a case where the metal material from the negative electrode end portion P was in contact with the insulating portion 40B of the negative electrode tab 40 was taken as "with spillage". In addition, as shown in Figure 16B , a case where the metal material from the negative electrode end portion P was not in contact with the insulating portion 40B of the negative electrode tab 40 was taken as "without spillage".

[0155] As shown in Figure 15 , in the case where the number of laminations X was 11 sheets, there was no "spillage" of the metal material in the laminate ST where the distance Y was 2.0 mm or more. In addition, in the case where the number of laminations X was 21 sheets, there was no "spillage" of the metal material in the laminate ST where the distance Y was 2.7 mm or more. From the results of Figure 15 , in order not to have spillage, it was considered that the distance Y and the number of laminations X needed to be in the relationship of Y > 0.048X + 1.3. As the number of laminations X increased, the distance Y at which there was no spillage increased, which was considered to be due to the fact that as the number of laminations X increased, the bonding interface increased, and thus the pressing force required for bonding increased, as a result of which the metal material was easily extruded.

[0156] <Experiment 2>

[0157] Figure 17 is a graph showing the results of Experiment 2. In Experiment 2, the plurality of laminates ST (E1 to E4, R1 to R3 shown in Figure 15 , which were manufactured in Experiment 1) were each used to manufacture a secondary battery of the structure shown in Figure 1 , and a cycle test was performed. In the cycle test, while the secondary battery 1 was subjected to a pressure of 50 kPa in a thermostat at 25°C, 0.3C charging-0.3C discharging was repeated for 100 cycles. Then, the capacity retention rate (%) at 100 cycles was measured. The capacity retention rate (%) is the ratio (A2 / A1 x 100) of the capacity (A2) of the secondary battery 1 at the end of 100 cycles to the capacity (Al) at the end of one cycle.

[0158] As shown in Figure 17As shown, the capacity retention rates of the secondary batteries formed of the laminates E1 to E4 in which no overflow of the metal material occurred were all 98% or more, which was very good compared to the secondary batteries formed of the laminates R1 to R3 in which the overflow of the metal material occurred. It is considered that this is because no insulation failure occurred between the negative electrode 10 and the sealing portion 102 of the sealing container 100.

[0159] Embodiments of the present disclosure further include the following aspects.

[0160] (Addendum 1)

[0161] A lithium secondary battery includes:

[0162] A laminate is formed by stacking a plurality of positive electrodes and negative electrodes in a stacking direction via a separator, one of the positive electrodes and the negative electrodes including a first current collector composed of a pair of conductive layers sandwiching a resin layer, the first current collector including a first end portion extending in a first direction different from the stacking direction;

[0163] A first electrode tab electrically connected to the first end portion includes a first joint trace formed by joining the first end portion, and a first insulating portion disposed apart from the first joint trace in the first direction by a distance and covered with an insulating material; and

[0164] A sealing container including a sealing portion, the sealing container configured to, while enclosing the laminate inside the sealing portion, sandwich the first insulating portion of the first electrode tab in the sealing portion and extract a portion of the first electrode tab to an outside of the sealing container.

[0165] (Addendum 2)

[0166] The lithium secondary battery according to Addendum 1, wherein the first joint trace in the first end portion is disposed inside the first direction outer edge of the first end portion by 2 mm or more.

[0167] (Addendum 3)

[0168] The lithium secondary battery according to Addendum 1, wherein the first joint trace in the first end portion is disposed inside the first direction outer edge of the first end portion by 2.5 mm or more.

[0169] (Addendum 4)

[0170] The lithium secondary battery according to Addendum 1, wherein, when the total number of the first current collectors included in the laminate is set to X and the distance between the first joint trace in the first end portion and the first direction outer edge of the first end portion is set to Y, the relationship Y > 0.048X + 1.3 is satisfied.

[0171] (Attachment 5)

[0172] The lithium secondary battery according to any one of Attachments 4, wherein the X is 10 or more.

[0173] (Attachment 6)

[0174] The lithium secondary battery according to any one of Attachments 1 to 5, wherein the first joint trace is a welding trace.

[0175] (Attachment 7)

[0176] The lithium secondary battery according to any one of Attachments 1 to 6, wherein the first joint trace includes, in a cross section in the stacking direction, a region in which the pair of conductive layers are integrated with each other.

[0177] (Attachment 8)

[0178] The lithium secondary battery according to any one of Attachments 1 to 5, wherein the first end portion and the first electrode tab are joined to each other via a metal sheet.

[0179] (Attachment 9)

[0180] The lithium secondary battery according to Attachment 8, wherein the first joint trace is a welding trace.

[0181] (Attachment 10)

[0182] The lithium secondary battery according to Attachment 8 or 9, wherein the first joint trace includes, in a cross section in the stacking direction, a region in which the pair of conductive layers and the metal sheet are integrated.

[0183] (Attachment 11)

[0184] The lithium secondary battery according to any one of Attachments 8 to 10, wherein the first end portion has a pre-joint trace formed by being joined to the metal sheet, the pre-joint trace being disposed at a position different from the first joint trace as viewed in the stacking direction.

[0185] (Attachment 12)

[0186] The lithium secondary battery according to any one of Attachments 1 to 11, wherein the first current collector is a negative electrode current collector of the negative electrode, and the first electrode tab is a negative electrode electrode tab connected to the negative electrode current collector.

[0187] (Attachment 13)

[0188] The lithium secondary battery according to any one of Attachments 1 to 12, wherein the sealed container is constituted by an aluminum laminate film.

[0189] (Paragraph 14)

[0190] The lithium secondary battery according to any one of Paragraphs 1 to 13, wherein the other of the positive electrode and the negative electrode includes a second current collector composed of a pair of conductive layers sandwiching a resin layer, the second current collector having a second end portion extending in a second direction different from the stacking direction.

[0191] (Paragraph 15)

[0192] The lithium secondary battery according to Paragraph 14, further comprising a second electrode tab electrically connected to the second end portion of the second current collector, the second electrode tab including: a second joint trace formed by joining with the second end portion; and a second insulating portion disposed apart from the second joint trace by a gap in the second direction and covered with an insulating material.

[0193] The sealed container is configured to sandwich the second insulating portion of the second electrode tab with the sealing portion and to take out a portion of the second electrode tab to the outside of the sealed container.

[0194] (Paragraph 16)

[0195] The lithium secondary battery according to Paragraph 14 or 15, wherein the first direction and the second direction are the same direction.

[0196] (Paragraph 17)

[0197] The lithium secondary battery according to Paragraph 14 or 15, wherein the first direction and the second direction are different directions.

[0198] Explanation of Reference Signs

[0199] 1 …… lithium secondary battery; 10 …… negative electrode; 20 …… separator; 30 …… positive electrode; 40 …… negative electrode tab; 40B …… insulating portion; 42 …… positive electrode tab; 42B …… insulating portion; 100 …… sealed container; 102 …… sealing portion; IL …… insulating material; M1, M2 …… metal sheet; P …… negative electrode end portion; Q …… positive electrode end portion; ST …… laminate; W1 …… first joint trace; W2 …… second joint trace; WP1, WP2 …… pre-joint trace

Claims

1. A lithium secondary battery, wherein, Possessing: a laminate obtained by laminating a plurality of positive electrodes and negative electrodes in a stacking direction by a separator, one of the positive electrodes and the negative electrodes including a first current collector composed of a pair of conductive layers sandwiching a resin layer, the first current collector possessing a first end portion extending in a first direction different from the stacking direction; a first electrode tab electrically connected to the first end portion, the first electrode tab including: a first joint trace formed by joining with the first end portion; and a first insulating portion disposed apart from the first joint trace in the first direction and covered with an insulating material; and a sealed container possessing a sealed portion, the sealed container configured to, while enclosing the laminate inside the sealed portion, sandwich the first insulating portion of the first electrode tab in the sealed portion and take a portion of the first electrode tab outside the sealed container.

2. The lithium secondary battery according to claim 1, wherein the first joint trace in the first end portion is disposed inside 2 mm or more from an outer edge of the first end portion in the first direction.

3. The lithium secondary battery according to claim 1, wherein the first joint trace in the first end portion is disposed inside 2.5 mm or more from an outer edge of the first end portion in the first direction.

4. The lithium secondary battery according to claim 1, wherein when a total number of the first current collectors included in the laminate is set as X and a distance between the first joint trace in the first end portion and an outer edge of the first end portion in the first direction is set as Y, a relationship Y > 0.048X + 1.3 is satisfied.

5. The lithium secondary battery according to claim 4, wherein the X is 10 or more.

6. The lithium secondary battery according to any one of claims 1 to 5, wherein the first joint trace is a welding trace.

7. The lithium secondary battery according to claim 6, wherein the first joint trace includes, in a cross section in the stacking direction, a region in which the pair of conductive layers are integrated with each other.

8. The lithium secondary battery according to any one of claims 1 to 5, wherein the first end portion and the first electrode tab are joined with each other via a metal sheet.

9. The lithium secondary battery according to claim 8, wherein the first joint trace is a welding trace.

10. The lithium secondary battery according to claim 9, wherein the first joint trace includes, in a cross section in the stacking direction, a region in which the pair of conductive layers and the metal sheet are integrated throughout a plurality of layers.

11. The lithium secondary battery according to claim 8, wherein the first end portion has a pre-joint trace formed by joining with the metal sheet, the pre-joint trace being disposed at a position different from the first joint trace as viewed from the stacking direction.

12. The lithium secondary battery according to any one of claims 1 to 5, wherein the first current collector is a negative current collector of the negative electrode, and the first electrode tab is a negative electrode tab connected to the negative current collector.

13. The lithium secondary battery according to claim 12, wherein the sealed container is composed of an aluminum laminate film.

14. The lithium secondary battery according to any one of claims 1 to 5, wherein the other of the positive electrode and the negative electrode includes a second current collector composed of a pair of conductive layers sandwiching a resin layer, the second current collector having a second end portion extending in a second direction different from the stacking direction.

15. The lithium secondary battery according to claim 14, wherein the lithium secondary battery further has a second electrode tab electrically connected to the second end portion of the second current collector, the second electrode tab including a second joint trace formed by joining with the second end portion, and a second insulating portion disposed apart from the second joint trace in the second direction by a gap and covered with an insulating material, the sealed container is configured to sandwich the second insulating portion of the second electrode tab with the sealed portion and to take out a portion of the second electrode tab to the outside of the sealed container.

16. The lithium secondary battery according to claim 14, wherein the first direction and the second direction are the same direction.

17. The lithium secondary battery according to claim 14, wherein the first direction and the second direction are different directions.

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