Battery and method for manufacturing battery

Abstract

To suppress the occurrence of a micro short circuit between a positive electrode sheet and a negative electrode sheet.SOLUTION: One end portion of the positive electrode body 51 in the widthwise direction is the positive electrode current collector 54 to which the positive electrode active material layers 52, 53 are not applied, one end portion of the negative electrode sheet 40 is the non-facing region G1 located closer to the 41St portion on one side than one end portion of the positive electrode active material layer, the outermost peripheral portion of the negative electrode body is the outer periphery constituting portion 40Mo located on the outer periphery side than the outermost peripheral portion of the positive electrode sheet, and the water repellent agent 47 is provided on the outer peripheral surface 41S of at least a part of the non-facing region at the upper end portion of the outer periphery constituting portion.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to batteries and methods for manufacturing batteries. [Background technology]

[0002] BACKGROUND ART Secondary batteries using an electrode assembly in which a positive electrode sheet including a positive electrode active material layer and a negative electrode sheet are stacked with a separator (separator sheet) interposed therebetween, and a nonaqueous electrolyte solution are known (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-055790 Summary of the Invention [Problem to be solved by the invention]

[0004] After the initial charge, secondary batteries may be subjected to high-temperature aging treatment to dissolve or precipitate metallic foreign matter that may have been mixed into the secondary battery during the manufacturing process. "High-temperature aging treatment" refers to keeping a secondary battery with a high SOC (State of Charge) at a high temperature (e.g., 60°C or higher) for a long period of time.

[0005] When a secondary battery is subjected to high-temperature aging treatment, there is a risk of micro-short circuits occurring in the outermost layer region of the electrode assembly. The "micro-short circuit" refers to a phenomenon in which a metal component contained in the positive electrode active material layer elutes into the nonaqueous electrolyte, causing local deposition of the metal component on the surface of the negative electrode facing the portion of the positive electrode from which the metal component has eluted, resulting in electrical connection between the positive electrode and the negative electrode.

[0006] For example, in a lithium-ion secondary battery, if the outermost periphery of the negative electrode assembly is located further outward than the outermost periphery of the positive electrode sheet, lithium ions that migrate from the positive electrode sheet to the negative electrode sheet near the positive electrode current collector during high-temperature aging may migrate via the nonaqueous electrolyte to the negative electrode active material layer at the outermost periphery of the negative electrode assembly. Furthermore, oxygen contained in the space within the case permeates through the outermost separator and reacts with the lithium ions that migrate to the negative electrode active material layer at the outermost periphery of the negative electrode assembly, inducing the elution of metal components from the positive electrode active material layer of the positive electrode sheet. This makes "micro-short circuits" more likely to occur during high-temperature aging. Micro-short circuits increase the self-discharge rate of the secondary battery.

[0007] The present disclosure has been made in consideration of the above circumstances, and has an object to provide a battery and a method for manufacturing the battery that can suppress the occurrence of micro-short circuits between a positive electrode sheet and a negative electrode sheet. [Means for solving the problem]

[0008] A battery according to a first aspect of the present disclosure includes a negative electrode assembly and a long strip-shaped negative electrode sheet having a negative electrode active material layer coated on each of both sides of the negative electrode assembly, a positive electrode assembly and a long strip-shaped positive electrode sheet having a positive electrode active material layer coated on each of both sides of the positive electrode assembly, a long strip-shaped separator positioned between the negative electrode sheet and the positive electrode sheet, a wound body formed by winding a laminate having the negative electrode sheet, the positive electrode sheet, and the separator around a predetermined axis, and a nonaqueous and a case that accommodates an electrolyte solution, wherein one end in the width direction of the positive electrode body is a positive electrode current collecting portion that is not coated with the positive electrode active material layer, the one end of the negative electrode sheet is a non-facing region located on the one side of the one end of the positive electrode active material layer, the outermost periphery of the negative electrode body is an outer periphery constituent portion that is located outer than the outermost periphery of the positive electrode sheet, and a water repellent agent is provided on at least a part of the outer periphery surface of the non-facing region at the upper end of the outer periphery constituent portion.

[0009] In a battery according to a first aspect of the present disclosure, a case contains a wound body formed by winding a laminate having a long strip-shaped negative electrode sheet, a long strip-shaped positive electrode sheet, and a long strip-shaped separator around a predetermined axis, and a nonaqueous electrolyte. The negative electrode sheet has a negative electrode body and a negative electrode active material layer coated on both sides of the negative electrode body. The positive electrode sheet has a positive electrode body and a positive electrode active material layer coated on both sides of the positive electrode body. The separator is located between the negative electrode sheet and the positive electrode sheet. One end in the width direction of the positive electrode body is a positive electrode current collector that is not coated with a positive electrode active material layer. One end of the negative electrode sheet is a non-facing region located on one side of one end of the positive electrode active material layer. The outermost periphery of the negative electrode body is a peripheral component located outer than the outermost periphery of the positive electrode sheet. Ions may migrate from one end of the outermost periphery of the positive electrode sheet to the negative electrode active material layer on the inner periphery of the outer peripheral component of the negative electrode sheet. These ions may flow into the nonaqueous electrolyte from one end of the inner periphery of the negative electrode active material layer in the non-opposing region of the outer peripheral component, and then migrate via the nonaqueous electrolyte to the negative electrode active material layer on the outer periphery of the non-opposing region. Furthermore, since nonaqueous electrolyte may not be present around the upper end of the wound body, a reaction between the ions that migrated to the outer periphery of the negative electrode active material layer and oxygen contained in the space within the case may be accelerated at the upper end of the non-opposing region of the negative electrode sheet. If this reaction is accelerated, metal components may be eluted from the positive electrode active material layer of the positive electrode sheet, making a micro-short circuit more likely to occur at one end of the upper end of the wound body.

[0010] Therefore, in the battery according to the first aspect of the present disclosure, a water repellent agent is provided on at least a portion of the outer peripheral surface of the non-facing region at the upper end of the outer peripheral component. This suppresses ion migration via the non-aqueous electrolyte to the negative electrode active material layer on the outer peripheral side of the non-facing region, compared to when the water repellent agent is not provided. This suppresses elution of metal components from the positive electrode active material layer of the positive electrode sheet, thereby suppressing the occurrence of micro-short circuits.

[0011] A battery according to a second aspect of the present disclosure has the configuration according to the first aspect, wherein the water repellent agent is provided over the entire circumferential direction of the outer circumferential surface of the non-opposing region of the outer circumferential constituent part.

[0012] In the battery according to the second aspect of the present disclosure, a water repellent agent is provided on the entire peripheral surface of the non-facing region of the peripheral component in the circumferential direction, thereby suppressing ion migration via the non-aqueous electrolyte to the negative electrode active material layer on the outer periphery of the non-facing region across the entire vertical area of ​​the non-facing region of the negative electrode sheet.

[0013] A battery according to a third aspect of the present disclosure has the configuration described in the first or second aspect, wherein the water repellent agent is provided over the entire width of the outer peripheral surface of the upper end of the outer peripheral component.

[0014] In the battery according to the third aspect of the present disclosure, it becomes easy to provide a water repellent agent on the outer peripheral surface of the non-facing region at the upper end of the outermost periphery of the negative electrode body.

[0015] In the battery according to a fourth aspect of the present disclosure, in any one of the first to third aspects, the surface tension of the water repellent agent is lower than the surface tension of the non-aqueous electrolyte.

[0016] In the battery according to the fourth aspect of the present disclosure, the surface tension of the water repellent agent is lower than that of the non-aqueous electrolyte, and therefore, ion migration to the negative electrode active material layer on the outer periphery of the non-facing region via the non-aqueous electrolyte is suppressed compared to when the surface tension of the water repellent agent is equal to or higher than that of the non-aqueous electrolyte.

[0017] In a battery according to a fifth aspect of the present disclosure, in any one of the first to fourth aspects, a part of the upper end of the outermost part of the positive electrode sheet is located on the inner circumferential side of a part of the upper end of the outer peripheral constituent part, and the upper end of the outermost part of the positive electrode sheet is located on the inner circumferential side of the remainder of the upper end of the outer peripheral constituent part.

[0018] In the battery according to the fifth aspect of the present disclosure, a part of the upper end of the outermost portion of the positive electrode sheet is located inside a part of the upper end of the outer peripheral constituent part, while the upper end of the outermost portion of the positive electrode sheet is not located inside the remainder of the upper end of the outer peripheral constituent part, so that a micro-short circuit is unlikely to occur between the remainder of the upper end of the outer peripheral constituent part and the upper end of the outermost portion of the positive electrode sheet.

[0019] A battery manufacturing method according to a sixth aspect of the present disclosure is a battery manufacturing method as set forth in claim 1, and includes the steps of applying the water repellent agent to the outer peripheral surface of at least a portion of the non-facing region at the upper end of the outer peripheral component before it becomes the wound body, and winding the negative electrode sheet, the positive electrode sheet, and the separator around the axis to manufacture the wound body. [Effects of the Invention]

[0020] According to the present disclosure, a battery and a method for manufacturing the battery are provided that can suppress the occurrence of micro-short circuits between a positive electrode sheet and a negative electrode sheet. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a perspective view showing the appearance of a secondary battery according to an embodiment; [Figure 2] 1 is an exploded perspective view of a secondary battery according to an embodiment; [Figure 3] FIG. 2 is an exploded perspective view of a positive electrode sheet, a separator, and a negative electrode sheet. [Figure 4] 4 is a cross-sectional view of the wound body shown in FIG. 2 taken along the arrow line 4-4. [Figure 5] 5 is a partially enlarged cross-sectional view of the wound body shown in FIG. 2 taken along the arrow line 5-5. [Figure 6] FIG. 2 is a schematic side view of a wound body manufacturing apparatus. [Figure 7] 1 is a flowchart showing a method for manufacturing a secondary battery. [Figure 8] 1 is a diagram illustrating the mechanism of a micro-short circuit occurring in a region that constitutes the outermost layer of a wound body. [Figure 9] 10 is a graph showing whether or not a micro-short circuit occurs relative to the amount of electrolyte in a secondary battery configured such that a wound body and a non-aqueous electrolyte are housed in a case. [Figure 10] FIG. 10 is a schematic diagram of a part of the outer peripheral surface of a negative electrode sheet of a first modified example. [Figure 11] FIG. 10 is a schematic diagram of a portion of the outer peripheral surface of a negative electrode sheet of a second modified example. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, a battery according to an embodiment will be described with reference to the drawings. The battery according to the embodiment is a lithium-ion secondary battery serving as a cell battery constituting a battery module used as an on-board power source for, for example, an electric vehicle, a hybrid vehicle, etc. In each drawing, arrow D indicates the longitudinal direction of a lithium-ion secondary battery 10 (hereinafter referred to as battery 10), arrow E indicates the depth direction of battery 10, and arrow F indicates the up-down direction of battery 10.

[0023] [Battery 10 Configuration] As shown in FIGS. 1 and 2, the battery 10 includes a lid assembly 20, a wound body (electrode body) 30, an insulating envelope 65, and a battery case (case) 70.

[0024] (battery case 70) The battery case 70 is made of, for example, aluminum and has a rectangular parallelepiped shape with an open top.

[0025] (lid assembly 20) The lid assembly 20 includes a lid member 21, a negative electrode current collector terminal 22 as a current collector terminal, a positive electrode current collector terminal 23 as a current collector terminal, a negative electrode external terminal 24 as an external terminal, and a positive electrode external terminal 25 as an external terminal.

[0026] <Cover member 21> The lid member 21 is made of, for example, aluminum, and is a plate-like member extending in the longitudinal direction D. The lid member 21 is provided with a safety valve 21A and a cap 26 that closes the injection port 21B.

[0027] The safety valve 21A opens when the internal pressure of the battery case 70 reaches a predetermined pressure, and discharges gas generated inside the battery case 70.

[0028] Inlet 21B is a through-hole that passes through lid member 21 in the vertical direction. Inlet 21B is used when injecting nonaqueous electrolyte 95 (described later) into battery case 70. Cap 26 is attached to inlet 21B in an airtight and liquid-tight manner by, for example, laser welding.

[0029] <Negative electrode current collecting terminal 22 and negative electrode external terminal 24> The negative electrode current collector terminal 22 and the negative electrode external terminal 24 are made of, for example, copper, and are provided at the other end of the lid member 21 in the longitudinal direction D. The negative electrode current collector terminal 22 is a rectangular plate-like member with its plate thickness direction aligned in the depth direction E. The negative electrode external terminal 24 is electrically connected to the negative electrode current collector terminal 22 and is exposed to the outside of the lid member 21.

[0030] <Positive electrode current collecting terminal 23 and positive electrode external terminal 25> The positive electrode current collector terminal 23 and the positive electrode external terminal 25 are made of, for example, aluminum, and are provided at one end of the lid member 21 in the longitudinal direction D. The positive electrode current collector terminal 23 is a rectangular plate-like member with its plate thickness direction aligned in the depth direction E. The positive electrode external terminal 25 is electrically connected to the positive electrode current collector terminal 23 and is exposed to the outside of the lid member 21.

[0031] (Wound body 30) As shown in FIG. 2, the wound body 30 has a power generating body 31, a negative electrode current collecting portion 46, and a positive electrode current collecting portion .

[0032] As shown in FIG. 3, the wound body 30 is composed of a laminate 62 having a long strip-shaped negative electrode sheet 40 as an electrode sheet, a long strip-shaped positive electrode sheet 50 as an electrode sheet, and two long strip-shaped separators 60A and 60B. The negative electrode sheet 40, the positive electrode sheet 50, and the separators 60A and 60B are flexible. As shown in FIGS. 3 and 8, the wound body 30 is composed by winding the laminate 62 around an imaginary axis IAX (see FIG. 3) extending in the width direction G of the negative electrode sheet 40, the positive electrode sheet 50, and the separators 60A and 60B. As shown in FIG. 2, the wound body 30 has a flat shape.

[0033] <Negative electrode sheet 40> As shown in FIG. 3, the negative electrode sheet 40 includes a long strip-shaped negative electrode body 41, a first negative electrode active material layer (negative electrode active material layer) 42 coated on one side of the negative electrode body 41, and a second negative electrode active material layer (negative electrode active material layer) 43 coated on the other side of the negative electrode body 41. The negative electrode body 41 is made of, for example, copper foil. The first negative electrode active material layer 42 and the second negative electrode active material layer 43 have an inner circumferential side negative electrode active material layer that is located on the negative electrode body 41 side, and an outer circumferential side negative electrode active material layer that is located on the opposite side from the negative electrode body 41. As shown in FIG. 3, the first negative electrode active material layer 42 and the second negative electrode active material layer 43 are coated only on regions of both sides of the negative electrode body 41 excluding the side portions on the other side opposite one side G1. Therefore, a negative electrode current collecting portion 46 on which the first negative electrode active material layer 42 and the second negative electrode active material layer 43 are not applied is formed at the other end of the negative electrode body 41 .

[0034] The first negative electrode active material layer 42 and the second negative electrode active material layer 43 contain a negative electrode active material and a negative electrode binder. The negative electrode active material is a material capable of absorbing and releasing lithium ions (for example, a carbon material (for example, natural graphite, artificial graphite, etc.)). Examples of the negative electrode active material include fluororesins (for example, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, etc.), polyvinyl acetate, etc.

[0035] 3 and 5, a water repellent agent 47 is provided in a specific region GS on a tip side LD1 in the longitudinal direction LD (see FIG. 3) (the circumferential direction in the wound body 30 described later) at an end portion on one side G1 of the outer peripheral surface 41S, which is the surface on the second negative electrode active material layer 43 side of the negative electrode body 41. The water repellent agent 47 is a water repellent agent containing, for example, a fluororesin (Poly Tetra Fluoro Ethylene).

[0036] <Positive electrode sheet 50> As shown in FIG. 3, the positive electrode sheet 50 includes a long strip-shaped positive electrode body 51, a first positive electrode active material layer (positive electrode active material layer) 52 coated on one surface of the positive electrode body 51, and a second positive electrode active material layer (positive electrode active material layer) 53 coated on the other surface of the positive electrode body 51. The first positive electrode active material layer 52 and the second positive electrode active material layer 53 have an inner peripheral side positive electrode active material layer which is a part on the side of the positive electrode body 51 and an outer peripheral side positive electrode active material layer which is a part on the side opposite to the positive electrode body 51. The positive electrode body 51 is made of, for example, an aluminum foil. As shown in FIG. 3, the first positive electrode active material layer 52 and the second positive electrode active material layer 53 are coated only on the region excluding the side portions on one side G1 of both surfaces of the positive electrode body 51. Therefore, a positive electrode current collector portion 54 where the first positive electrode active material layer 52 and the second positive electrode active material layer 53 are not coated is formed at the end of one side G1 of the positive electrode body 51.

[0037] The first positive electrode active material layer 52 and the second positive electrode active material layer 53 contain a positive electrode active material and a positive electrode binder. The positive electrode active material is a material capable of occluding and releasing lithium ions. Examples of the positive electrode active material include lithium nickel-based oxides, lithium cobalt-based oxides (e.g., LiCoO2, etc.), and lithium manganese-based oxides (e.g., LiMn2O4). Examples of the lithium nickel-based oxides include LiCoO2, ternary lithium transition metal oxides, and solid solution type lithium-excess transition metal oxides. The ternary lithium transition metal oxide is represented by the general formula (A): Li(LiaMnxCoyNiz)O2 (where a, x, y, z in the formula (A) satisfy a + x + y + z ≒ 1 and xyz ≠ 0). The solid solution type lithium-excess transition metal oxide is represented by the general formula (B): xLi[Li1 / 3Mn2 / 3]O2·(1 - x)LiMeO2 (where Me is one or more transition metals and x satisfies 0 < x ≦ 1). Examples of the positive electrode binder include fluororesins (e.g., polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, etc.), polyvinyl acetate, etc. The positive electrode active material layer may contain, as necessary, a conductive aid (e.g., acetylene black, etc.), a thickener, a surfactant, a dispersant, a wetting agent, an antifoaming agent, etc.

[0038] <Separators 60A and 60B> The separators 60A and 60B are made of an insulating material such as polypropylene or polyethylene. Each of the separators 60A and 60B maintains a gap between the positive electrode sheet 50 and the negative electrode sheet 40 to prevent short circuits and also holds the nonaqueous electrolyte solution 95. The separators 60A and 60B are, for example, porous resin flat plates.

[0039] 3 and 5, the separators 60A and 60B have a larger dimension in the width direction G than the negative electrode sheet 40 and the positive electrode sheet 50. The separator 60B faces the first negative electrode active material layer 42 of the negative electrode sheet 40 and the second positive electrode active material layer 53 of the positive electrode sheet 50, and the separator 60A faces the second negative electrode active material layer 43 of the negative electrode sheet 40. That is, the separator 60A, the negative electrode sheet 40, the separator 60B, and the positive electrode sheet 50 are stacked in this order, and the negative electrode sheet 40, the positive electrode sheet 50, and the separators 60A and 60B form a laminate 62. Although not shown in the drawings, an end of one side G1 of the positive electrode current collector 54 of the positive electrode body 51 is located on one side G1 of the separators 60A and 60B. Similarly, the other end of the negative electrode current collecting portion 46 of the negative electrode body 41 in the width direction G is located on the other side in the width direction G of the separators 60A, 60B.

[0040] The separator 60A, the negative electrode sheet 40, the separator 60B, and the positive electrode sheet 50 are formed into a laminate 62 by a manufacturing apparatus 80 shown in FIG. 6. More specifically, the separator 60A, the negative electrode sheet 40, the separator 60B, and the positive electrode sheet 50 are formed into a substantially cylindrical wound body (not shown) by the manufacturing apparatus 80. The manufacturing apparatus 80 includes a driven roller 81, a driven roller 82, a driven roller 83, a driven roller 84, and a take-up roller 85, which are parallel to one another. The negative electrode body 41 is wound around the driven roller 81, the positive electrode body 51 is wound around the driven roller 82, the separator 60B is wound around the driven roller 83, and the separator 60A is wound around the driven roller 84. The negative electrode body 41, the positive electrode body 51, the separator 60A, and the leading ends of the separator 60B are wound around a winding roller 85 while being stacked in the order of separator 60A, negative electrode sheet 40, separator 60B, and positive electrode sheet 50. A drive device 86 is connected to the winding roller 85 via a power transmission mechanism (not shown). The drive device 86 is, for example, an electric motor. A control device 87 is further connected to the drive device 86. The control device 87 is configured to include a CPU (Central Processing Unit: processor), ROM (Read Only Memory), RAM (Random Access Memory), storage, a communication I / F (Interface), and an input / output I / F. The CPU, ROM, RAM, storage, communication I / F, and input / output I / F are connected to each other so as to be able to communicate with each other via a bus.

[0041] The manufacturing apparatus 80 further includes a water repellent application device 88 positioned directly above the outer circumferential surface 41S of the negative electrode body 41 located downstream of the driven roller 81.

[0042] Furthermore, although not shown, the manufacturing apparatus 80 has a pair of negative electrode coating devices and a negative electrode drying oven located directly above and below the negative electrode body 41 and located downstream of the water repellent applicator 88. Furthermore, although not shown, the manufacturing apparatus 80 has a pair of positive electrode coating devices and a positive electrode drying oven located downstream of the driven roller 82 and directly above and below the positive electrode body 51. The manufacturing apparatus 80 also has a cutting device.

[0043] The driving device 86, the water repellent application device 88, the negative electrode coating device, the negative electrode drying furnace, the positive electrode coating device, the positive electrode drying furnace, and the cutting device are controlled by a control device 87.

[0044] A battery manufacturing system including manufacturing apparatus 80 operates according to the steps in the flowchart of Fig. 7. When drive device 86 starts in S10, take-up roller 85 rotates at a constant speed in the direction of arrow RD shown in Fig. 6. This rotates driven rollers 81, 82, 83, and 84, and separator 60A, negative electrode sheet 40, separator 60B, and positive electrode sheet 50 are gradually taken up by take-up roller 85.

[0045] Furthermore, in S11, the water repellent application device 88 controlled by the control device 87 sprays the water repellent 47 onto the outer peripheral surface 41S of the negative electrode body 41 at predetermined time intervals for a predetermined period of time. More specifically, as shown in Fig. 3, the water repellent 47 is sprayed onto a specific region GS that is part of each non-facing region 41St of the negative electrode body 41. The non-facing region 41St will be described later.

[0046] Furthermore, in S12, a pair of negative electrode coaters coat both surfaces of the negative electrode body 41 with a first negative electrode active material layer 42 and a second negative electrode active material layer 43. That is, the second negative electrode active material layer 43 is coated on top of the water repellent agent 47. Furthermore, the first negative electrode active material layer 42 and the second negative electrode active material layer 43 are dried in a negative electrode drying furnace.

[0047] Furthermore, in S13, a first positive electrode active material layer 52 and a second positive electrode active material layer 53 are coated on both surfaces of the positive electrode body 51 downstream of the driven roller 82 by a pair of positive electrode coating devices, and the first positive electrode active material layer 52 and the second positive electrode active material layer 53 are then dried in a positive electrode drying furnace.

[0048] Furthermore, in S14, the separator 60A, the negative electrode sheet 40, the separator 60B, and the positive electrode sheet 50 are cut at their respective predetermined positions by a cutting device.

[0049] As a result, the laminate 62 becomes a substantially cylindrical wound body (not shown). That is, the laminate 62 is wound around the imaginary axis IAX.

[0050] Furthermore, in S15, a pressing step is carried out by the battery manufacturing system. This presses the wound body formed into a substantially cylindrical shape, and the substantially flat wound body 30 shown in FIG. 4 is obtained. As shown in FIG. 2, the positive electrode current collector 54 is wound to form an end portion on one side G1 of the wound body 30, and the negative electrode current collector 46 is wound to form an end portion on the other side of the wound body 30. Furthermore, the region between the negative electrode current collector 46 and the positive electrode current collector 54 of the wound body 30 is the power generating body 31. The power generating body 31 has the function of storing electrical energy for the battery 10.

[0051] Furthermore, in S16, the battery manufacturing system performs a terminal welding process. As a result, the lower end of the negative electrode current collector terminal 22 is connected to the vertical center of the negative electrode current collector 46 of the wound body 30 by resistance welding, and the lower end of the positive electrode current collector terminal 23 is connected to the vertical center of the positive electrode current collector 54 by ultrasonic welding. Therefore, as shown in FIG. 2, the end on the other side of the wound body 30 is deformed, and the end on the other side of the wound body 30 is collected. Furthermore, the end on one side G1 of the wound body 30 is deformed, and the end on one side G1 of the wound body 30 is collected. Furthermore, the battery manufacturing system accommodates the integrated negative electrode current collector terminal 22, positive electrode current collector terminal 23, wound body 30, and insulating bag 65 in the internal space of the battery case 70. Furthermore, a lid member 21 is attached to the upper end of the battery case 70 by, for example, laser welding, so as to close the upper end opening. Furthermore, after this, a cell drying process is carried out by the battery manufacturing system. The insulating envelope 65 houses the wound body 30, thereby electrically insulating the wound body 30 from the lid member 21 and the battery case .

[0052] 4, in this state, the specific region GS (water repellent agent 47) is located at the upper end 30UP of the wound body 30. Here, the upper end 30UP of the wound body 30 is the upper part of the wound body 30 as shown in FIG. 4, and is a part whose outer circumferential surface has an R-shaped cross section.

[0053] Furthermore, in S17, the battery manufacturing system performs a liquid injection and sealing process. In the liquid injection and sealing process, nonaqueous electrolyte 95 is injected through injection port 21B formed in lid member 21, and cap 26 is attached to injection port 21B by, for example, laser welding. This completes battery 10 shown in FIG. 1.

[0054] The nonaqueous electrolyte 95 of this embodiment contains an electrolyte and a nonaqueous solvent. Examples of the electrolyte include fluorine-containing lithium salts (e.g., lithium hexafluorophosphate, lithium tetrafluoroborate, etc.) and fluorine-free lithium salts (e.g., lithium perchlorate, lithium tetrachloroaluminate, etc.). Examples of the nonaqueous solvent include cyclic carbonates (e.g., ethylene carbonate, etc.) and chain carbonates (e.g., dimethyl carbonate, ethyl methyl carbonate, etc.). The nonaqueous electrolyte 95 may further contain an additive (e.g., lithium bis(oxalato)borate, etc.).

[0055] The surface tension of the water repellent agent 47 is smaller than the surface tension of the non-aqueous electrolyte 95 when the battery 10 is in a completed state.

[0056] Furthermore, in S18, the battery manufacturing system performs an activation process, in which the battery 10 is initially charged and then stored at a high temperature for a certain period of time, undergoing a high-temperature aging process that dissolves metallic foreign matter and stabilizes the SEI (Solid Electrolyte Interphase) coating.

[0057] (Action and effect) The operation and effects of this embodiment will be described below.

[0058] However, when high-temperature aging is performed on battery 10 configured such that oxygen contained in the space within battery case 70 is likely to come into contact with second negative electrode active material layer 43, which is the outermost negative electrode active material layer of wound body 30, a micro-short circuit may occur near positive electrode current collector 54. The mechanism by which such a micro-short circuit occurs will be described below with reference to FIG.

[0059] 8 shows the outermost layer portion at the end of one side G1 of the wound body 30 of the battery 100 according to the comparative example. The battery 100 according to the comparative example has the same structure as the battery 10 of the embodiment except that it does not have the water repellent agent 47. Therefore, the same components of the battery 100 as those of the battery 10 are designated by the same reference numerals and detailed description thereof will be omitted.

[0060] In the region constituting the outermost layer of the wound body 30 of the battery 100, the end of one side G1 of the separator 60A constituting the outer surface of the wound body 30 contacts a portion of the negative electrode sheet 40 corresponding to the non-facing region 41St of the second negative electrode active material layer 43 and covers the negative electrode sheet 40 from the one side G1. Here, the non-facing region 41St refers to a portion of the negative electrode sheet 40 that is located on the one side G1 of the positive electrode sheet 50 from the end of the one side G1 of the positive electrode sheet 50. Thus, in the battery 100, the outermost portion of the negative electrode sheet 40 is located on the inner periphery of the outermost region of the separator 60A. This outermost portion of the negative electrode sheet 40 is referred to as the outer peripheral portion 40Mo. Therefore, the portion of the positive electrode sheet 50 facing the outer peripheral portion 40Mo contributes to the battery reaction of the battery 100, thereby increasing the energy density. On the other hand, in the battery 100, when oxygen contained in the upper space inside the battery case 70 permeates the separator 60A, the oxygen is likely to come into contact with the second negative electrode active material layer 43, which is the outermost layer.

[0061] In the high-temperature aging treatment, a battery 100 with a high SOC (for example, 3.97 V) is used. In a battery 100 with a high SOC, many lithium ions are present in a region facing the second positive electrode active material layer 53 in the first negative electrode active material layer 42 on the inner circumferential side constituting the outer circumferential component 40Mo of the negative electrode sheet 40. On the other hand, it is believed that almost no lithium ions are present in the non-facing region 41St of the first negative electrode active material layer 42 of the outer circumferential component 40Mo, which does not face the second positive electrode active material layer 53. It is also believed that almost no lithium ions are present in the second negative electrode active material layer 43 on the outer circumferential side constituting the outer circumferential component 40Mo.

[0062] As shown in FIG. 8, when high-temperature aging treatment is performed on the battery 100 in a high SOC state, lithium ions 90 migrate from the second positive electrode active material layer 53 constituting the outermost region of the positive electrode sheet 50 to the first negative electrode active material layer 42 of the outer peripheral component portion 40Mo.

[0063] In the outer peripheral component 40Mo, due to the difference in concentration of lithium ions 90, the lithium ions 90 present in the region of the first negative electrode active material layer 42 facing the second positive electrode active material layer 53 move to the non-facing region 41St that does not face the second positive electrode active material layer 53 of the first negative electrode active material layer 42 (in the direction of arrow D1 in Figure 8).

[0064] The lithium ions 90 that have migrated to the portion of the first negative electrode active material layer 42 included in the non-opposing region 41St flow out from the end face ES of one side G1 of the first negative electrode active material layer 42 into the non-aqueous electrolyte 95 present in the region 30S between the end face ES and the separator 60A due to the difference in concentration of the lithium ions 90, and then migrate to the end face ES of the second negative electrode active material layer 43 of the outer peripheral component part 40Mo (in the direction of arrow D2) via the non-aqueous electrolyte 95. At this time, when a part (region 60AS) of the outermost peripheral part 60A-1 of the separator 60A comes into contact with the end face 40ES of the negative electrode sheet 40, a migration path for the lithium ions 90 to the second negative electrode active material layer 43 is easily formed via the non-aqueous electrolyte 95 held in the region 60AS facing the end face ES of the separator 60A.

[0065] When oxygen contained in the battery case 70 permeates through the separator 60A, the second negative electrode active material layer 43 of the outer peripheral component 40Mo comes into contact with the oxygen. As a result, the lithium ions 90 that have migrated to the second negative electrode active material layer 43 of the outer peripheral component 40Mo react with the oxygen, forming a coating 45 on the surface of the second negative electrode active material layer 43. In other words, the lithium ions 90 that have migrated to the outermost second negative electrode active material layer 43 react with oxygen and are consumed. Due to the consumption of the lithium ions 90 caused by the formation of this coating 45, the migration of the lithium ions 90 to the non-facing region 41St in the first negative electrode active material layer 42 is accelerated.

[0066] As the lithium ions 90 move in this manner, the potential of the end portion of the first negative electrode active material layer 42 adjacent to the non-facing region 41St in the region facing the positive electrode sheet 50 rises locally. Furthermore, due to the local potential leveling, the potential of the end portion of one side G1 of the second positive electrode active material layer 53 (the portion facing the end portion of the first negative electrode active material layer 42 adjacent to the non-facing region 41St) rises. In other words, the outermost peripheral region of the positive electrode sheet 50 locally experiences an overvoltage (for example, 4.3 V or higher).

[0067] When an overvoltage occurs in the positive electrode sheet 50, the crystalline structure of the second positive electrode active material layer 53 collapses, and the metal component 44 contained in the second positive electrode active material layer 53 is more likely to dissolve into the non-aqueous electrolyte 95. The metal component 44 that dissolves into the non-aqueous electrolyte 95 is more likely to deposit on the surface of the first negative electrode active material layer 42 at a portion facing the second positive electrode active material layer 53. As a result, a metal deposit 48 that electrically connects the positive electrode sheet 50 and the negative electrode sheet 40 is formed on the surface of the first negative electrode active material layer 42. As a result, a micro-short circuit occurs between the first negative electrode active material layer 42 and the second positive electrode active material layer 53.

[0068] To verify the mechanism of such micro-short circuit occurrence, a correlation was examined between the presence or absence of micro-short circuits in the vicinity of the positive electrode current collector 54 in the region constituting the outermost layer of the wound body 30 of the battery 100 according to the comparative example and the amount of nonaqueous electrolyte 95 in the battery case 70. By adjusting the amount of nonaqueous electrolyte 95 in the battery case 70, it is possible to adjust the amount of nonaqueous electrolyte 95 present in the region 30S in the battery case 70 and the outermost peripheral portion 60A-1 (portion 60AS) of the separator 60A. When the amount of nonaqueous electrolyte 95 present in the region 30S and the outermost peripheral portion 60A-1 changes in this way, the ease of migration of lithium ions 90 from the first negative electrode active material layer 42 to the second negative electrode active material layer 43 via the nonaqueous electrolyte 95 changes.

[0069] 9, the horizontal axis indicates the amount of nonaqueous electrolyte 95 in the battery case 70, and the vertical axis indicates the presence or absence of a micro-short circuit at the upper end 30UP of the wound body 30. The amount of nonaqueous electrolyte 95 on the horizontal axis is expressed as an index of the amount of electrolyte in each comparative example, with Comparative Example 1, in which a micro-short circuit occurred near the positive electrode current collector 54 in the region constituting the outermost layer of the wound body 30, being set as 100%. In Comparative Example 1, in which the amount of nonaqueous electrolyte 95 was set to 100%, a micro-short circuit occurred near the positive electrode current collector 54 in the region constituting the outermost layer of the wound body 30.

[0070] On the other hand, in Comparative Example 2, in which the amount of nonaqueous electrolyte 95 was set to 74% (%), no micro-short circuit occurred. This is thought to be because in Comparative Example 2, in which the amount of nonaqueous electrolyte 95 in the battery case 70 was smaller than in Comparative Example 1, the movement of lithium ions 90 (arrow D2 in FIG. 8 ) mediated by the nonaqueous electrolyte 95 was suppressed in the outer peripheral component portion 40Mo of the negative electrode sheet 40. That is, in Comparative Example 2, the amount of lithium ions 90 that migrate from the first negative electrode active material layer 42 to the second negative electrode active material layer 43 was small, so that the outermost peripheral region of the positive electrode sheet 50 did not experience an overvoltage, and therefore no micro-short circuit occurred.

[0071] Furthermore, no micro-short circuit occurred in Comparative Example 3, in which the amount of nonaqueous electrolyte 95 was set to 140%. This is thought to be because, in Comparative Example 3, in which the amount of nonaqueous electrolyte 95 in the battery case 70 is greater than in Comparative Example 1, the nonaqueous electrolyte 95 is injected up to the upper region of the battery case 70, thereby preventing the upper end 30UP of the wound body 30 from coming into contact with the air contained in the space within the battery case 70. That is, in Comparative Example 3, the amount of oxygen that permeates the outermost peripheral portion 60A-1 of the separator 60A is small, so consumption of lithium ions 90 by oxygen within the battery case 70 is prevented, and no micro-short circuit occurs.

[0072] As shown in FIG. 9, the verification results for Comparative Examples 1 to 3 all demonstrate the effectiveness of the mechanism of occurrence of micro-short circuits shown in FIG. 8. This reveals that the occurrence of micro-short circuits can be suppressed by some means of suppressing the migration of lithium ions 90 from the first negative electrode active material layer 42 to the second negative electrode active material layer 43 via the nonaqueous electrolyte solution 95. Therefore, in this embodiment, as shown in FIG. 3, a water repellent agent 47 is provided in a specific region GS on the leading end side LD1 in the longitudinal direction (circumferential direction) LD of the non-facing region 41St of the outer peripheral surface 41S, which is the surface of the negative electrode body 41 facing the second negative electrode active material layer 43. As shown in FIG. 4, in the wound body 30, the water repellent agent 47 (specific region GS) is included in the upper end portion 30UP of the wound body 30.

[0073] The amount of nonaqueous electrolyte 90 is likely to be smaller around the upper end 30UP of the wound body 30 in the space within the battery case 70 than in the region below the upper end 30UP. Therefore, in the non-facing region 41St of the negative electrode sheet 40 included in the upper end 30UP, a reaction between the lithium ions 90 that have migrated to the outermost second negative electrode active material layer 43 and oxygen contained in the space within the battery case 70 may be accelerated.

[0074] However, in the battery 10 of this embodiment, a water repellent agent 47 is provided in the non-facing region 41St (specific region GS) of the outer peripheral component 40Mo included in the upper end portion 30UP. That is, as shown in FIG. 5 , the water repellent agent 47 provided in the specific region GS extends over the entire width direction G of the non-facing region 41St. Therefore, compared to when the water repellent agent 47 is not provided, the migration of lithium ions 90 from the first negative electrode active material layer 42 to the second negative electrode active material layer 43 via the non-aqueous electrolyte solution 90 is more suppressed. In particular, the surface tension of the water repellent agent 47 of this embodiment is smaller than the surface tension of the non-aqueous electrolyte solution 95. Therefore, compared to when the surface tension of the water repellent agent 47 is equal to or greater than the surface tension of the non-aqueous electrolyte solution 90, the migration of lithium ions 90 from the first negative electrode active material layer 42 to the second negative electrode active material layer 43 via the non-aqueous electrolyte solution 95 is more likely to be suppressed. This prevents the metal component 44 contained in the second positive electrode active material layer 53 from eluting into the non-aqueous electrolyte solution 95, thereby suppressing the occurrence of the micro-short circuit.

[0075] 4, a part of the upper end of the outermost portion of the positive electrode sheet 50 is located on the inner periphery of a part (the right-hand region in FIG. 4) of the outer peripheral constituent portion 40Mo of the negative electrode sheet 40 included in the upper end portion 30UP, while the upper end of the outermost portion of the positive electrode sheet 50 is not located on the inner periphery of the remainder (the left-hand region in FIG. 4) of the outer peripheral constituent portion 40Mo included in the upper end portion 30UP. Therefore, a micro-short circuit is less likely to occur between the outer peripheral constituent portion 40Mo and the outermost portion of the positive electrode sheet 50 than when the upper end of the outer peripheral constituent portion 40Mo is located on the inner periphery of the entire region included in the upper end portion 30UP of the outer peripheral constituent portion 40Mo.

[0076] Although the battery and the method for manufacturing the battery according to the embodiment have been described above, the design of the battery and the method for manufacturing the battery can be modified as appropriate within the scope of the gist of the present invention.

[0077] For example, the present invention may be practiced in the form of a first modified example shown in Fig. 10. In this first modified example, a water repellent agent 47 is provided in a non-facing region 41St of the outer peripheral surface 41S of the negative electrode body 41, over an extended region ES that is longer in the longitudinal direction (circumferential direction) LD of the negative electrode sheet 40 than the specific region GS. When this negative electrode body 41 is used to form a wound body 30, the water repellent agent 47 is formed over one circumference of the outer peripheral constituent portion 40Mo of the negative electrode sheet 40. Therefore, over the entire vertical area of ​​the non-facing region 41St of the negative electrode sheet 40, migration of lithium ions 90 from the first negative electrode active material layer 42 to the second negative electrode active material layer 43 via the non-aqueous electrolyte solution 95 is suppressed.

[0078] The present invention may also be implemented in the form of a second modified example shown in FIG. 11 . In this second modified example, a water repellent agent 47 is applied over the entire width direction G of the outer peripheral surface 41S of the outer peripheral constituent portion 40Mo of the negative electrode body 41. When this negative electrode body 41 is used to form a wound body 30, the water repellent agent 47 is applied over the entire width direction G of the upper end portion 30UP of the outer peripheral constituent portion 40Mo of the negative electrode sheet 40. Therefore, when manufacturing the negative electrode sheet 40 of the second modified example using the manufacturing apparatus 80, there is no problem even if the accuracy of the spray position of the water repellent agent 47 in the width direction G by the water repellent agent application device 88 is lower than when the water repellent agent 47 is applied only to the specific region GS. Therefore, in the second modified example, it is easy to apply the water repellent agent 47 to the outer peripheral surface 41S of the non-facing region 41St at the upper end portion 30UP of the outer peripheral constituent portion 40Mo. Therefore, the negative electrode sheet 40 of the second modified example is easy to manufacture.

[0079] A water repellent agent 47 may be provided on at least a portion of the non-facing region 41St of the negative electrode sheet 40 in the width direction G.

[0080] The upper end 30UP of the wound body 30 may be a region narrower than the region shown in Fig. 4. For example, like the upper end 30UP-X shown in Fig. 4, the upper end of the wound body 30 may be a region between the upper end of the wound body 30 and a region above the lower end of the part of the upper side of the wound body 30 whose cross section has an R-shape.

[0081] The surface tension of the water repellent agent 47 may be equal to or greater than the surface tension of the non-aqueous electrolyte 95 . [Explanation of symbols]

[0082] 10 Lithium-ion secondary battery (battery) 30 Wound body (electrode body) 30UP Upper end 40 Negative electrode sheet 40Mo outer periphery 41 negative electrode body 41S outer surface 41St Non-opposing area 42 First negative electrode active material layer (negative electrode active material layer) 43 Second negative electrode active material layer (negative electrode active material layer) 50 positive electrode sheet 51 Positive electrode body 52 First positive electrode active material layer (positive electrode active material layer) 53 Second positive electrode active material layer (positive electrode active material layer) 54 Positive electrode current collector 60A separator 60B separator 62 Laminate 70 Battery case (case)

Claims

1. a negative electrode body; and a long strip-shaped negative electrode sheet having a negative electrode active material layer coated on each of both surfaces of the negative electrode body; a positive electrode body and a long strip-shaped positive electrode sheet having positive electrode active material layers coated on both sides of the positive electrode body; a long strip-shaped separator positioned between the negative electrode sheet and the positive electrode sheet; a wound body in which a laminate having the negative electrode sheet, the positive electrode sheet, and the separator is wound around a predetermined axis, and a case that accommodates a nonaqueous electrolyte; Equipped with one end portion in the width direction of the positive electrode body is a positive electrode current collecting portion on which the positive electrode active material layer is not coated, the one end of the negative electrode sheet is a non-facing region located on the one side of the one end of the positive electrode active material layer, the outermost peripheral portion of the negative electrode body is an outer peripheral component located outer than the outermost peripheral portion of the positive electrode sheet, A battery in which a water repellent agent is provided on at least a part of the outer peripheral surface of the non-facing region at the upper end of the outer peripheral constituent part.

2. The battery according to claim 1 , wherein the water repellent agent is provided on the entire outer peripheral surface of the non-facing region of the outer peripheral constituent part in the circumferential direction.

3. The battery according to claim 1 or 2, wherein the water repellent agent is provided over the entire outer peripheral surface of the upper end of the outer peripheral constituent part in the width direction.

4. 3. The battery according to claim 1, wherein the surface tension of the water repellent agent is lower than the surface tension of the non-aqueous electrolyte.

5. 3. The battery according to claim 1, wherein a portion of the upper end of the outermost portion of the positive electrode sheet is located on the inner circumferential side of a portion of the upper end of the outer peripheral constituent portion, and the upper end of the outermost portion of the positive electrode sheet is not located on the inner circumferential side of the remainder of the upper end of the outer peripheral constituent portion.

6. A method for manufacturing the battery according to claim 1, applying the water repellent agent to at least a part of the outer peripheral surface of the non-facing region at the upper end of the outer peripheral constituent part before it becomes the wound body; and a step of winding the negative electrode sheet, the positive electrode sheet, and the separator around the axis to manufacture the wound body; A method for manufacturing a battery having the above structure.

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