Nonaqueous electrolyte secondary battery

Abstract

This nonaqueous electrolyte secondary battery includes a flat electrode body (60) in which a first electrode (30) having a first electrode tab (22) connected thereto and a second electrode having a second electrode tab (24) connected thereto are wound with a separator (70) interposed therebetween. The separator (70) has an adhesive layer and is bonded to the first electrode (30) and the second electrode. The first electrode tab (22) is attached to an exposed core portion located within one turn from the winding end of a first mixture layer toward the winding start side, the exposed core portion being sandwiched between two first mixture layers separated from each other in the winding direction of the first electrode. A tape (57) is attached to the end of the electrode body (60) on the opposite side from the lead-out side of each electrode tab (22) so as to extend across both surfaces of the electrode body (60) in the thickness direction.

Description

Non-aqueous electrolyte secondary battery

[0001] The present disclosure relates to a non-aqueous electrolyte secondary battery, and particularly relates to suppressing voltage drop caused by drop impact.

[0002] Conventionally, non-aqueous electrolyte secondary batteries such as lithium ion batteries have been used as power sources for electronic devices including smartphones, tablet terminals, and notebook PCs. In this case, secondary batteries are particularly required to be lightweight and thinner.

[0003] For this reason, it has been considered to use, as a power source for electronic devices, a secondary battery in which an electrode assembly is housed in a flat outer package made of a metal laminated resin sheet as described in Patent Document 1. The electrode assembly has a positive electrode connected with a positive electrode tab and a negative electrode connected with a negative electrode tab, and is formed into a flat shape in which the positive electrode and the negative electrode are wound with a separator interposed therebetween. The positive electrode tab and the negative electrode tab are electrode tabs led out from the same axial end of the electrode assembly. Further, in order to increase the capacity recovery rate of the battery even after being left at high temperature, a first winding stopping tape is attached to pass through the tab lead-out end face of the electrode assembly, the end face opposite to the tab lead-out side, and both side wall surfaces parallel to the axial direction of the electrode assembly, and a second winding stopping tape is attached to the outer periphery of the electrode assembly in the winding direction.

[0004] Japanese Patent Application Laid-Open No. 2001-185224

[0005] In a configuration using a flat electrode assembly as described in Patent Document 1, in order to improve insulation between electrodes, it is conceivable to provide an adhesive layer on the separator and bond the separator to the positive electrode and the negative electrode via the adhesive layer. In addition, in a secondary battery or the like using an outer package made of a metal laminated resin sheet, a first electrode tab, which is a positive electrode tab or a negative electrode tab, may be arranged near the outer periphery of the electrode assembly. However, in this case, due to the thickness of the first electrode tab, the flatness of the surface perpendicular to the thickness direction of the outer peripheral surface of the electrode assembly is reduced, which may result in areas where the separator is insufficiently bonded. As a result, the separator may curl during drop impact of the secondary battery, causing voltage drop.

[0006] Therefore, the purpose of this disclosure is to suppress voltage drop caused by impact when the first electrode tab is positioned near the outer circumference of the electrode body in a non-aqueous electrolyte secondary battery.

[0007] The non-aqueous electrolyte secondary battery according to this disclosure comprises a flat electrode body in which a first electrode to which a first electrode tab is connected and a second electrode to which a second electrode tab is connected are wound via a separator, the first electrode tab and the second electrode tab are led out from the same end in the winding axis direction of the electrode body, the separator has an adhesive layer and is bonded to the first electrode and the second electrode by the adhesive layer, the first electrode has a first core body and a first compound layer provided on the first core body, and the first electrode tab is wound around the first compound layer from the winding end towards the winding start side This is a non-aqueous electrolyte secondary battery, wherein the core body exposed portion located within a certain range, where the first compound layer of the first core body is not provided, is attached to a portion sandwiched between two first compound layers that are separated from each other in the winding direction of the first electrode, the second electrode tab is located on the same half side divided at the center in the thickness direction of the electrode body with respect to the first electrode tab, and is positioned closer to the center in the thickness direction of the electrode body than the first electrode tab, and furthermore, tape is attached across both sides in the thickness direction of the electrode body to the end of the electrode body opposite to the lead-out side of the first electrode tab and the second electrode tab.

[0008] In the non-aqueous electrolyte secondary battery according to this disclosure, the separator is bonded to the first electrode and the second electrode. Furthermore, the first electrode tab, which is positioned near the outer circumference of the electrode body, is attached to the exposed core portion sandwiched between two first compound layers that are spaced apart in the winding direction of the first electrode. This allows the reduction in the flatness of the surface perpendicular to the thickness direction of the outer surface of the electrode body caused by the first electrode tab to be suppressed by the thickness of the first compound layer. Therefore, while suppressing poor adhesion of the separator, peeling of the separator can be suppressed. In addition, the ends of the separator are more easily fixed with tape by the tape attached to the end of each electrode tab of the electrode body opposite to the lead-out side. This further suppresses peeling of the separator. Therefore, in a non-aqueous electrolyte secondary battery, when the first electrode tab is positioned near the outer circumference of the electrode body, peeling of the separator due to impact from dropping can be suppressed, thereby suppressing voltage drop.

[0009] This is a perspective view of the non-aqueous electrolyte secondary battery of the embodiment. This is a schematic partial cross-sectional view of the non-aqueous electrolyte secondary battery of the embodiment, taken in a cross-section that passes through the positive electrode tab and includes the thickness direction and the winding axis direction of the electrode body. This is a schematic view of the electrode body of the non-aqueous electrolyte secondary battery of Figure 1 as seen in the thickness direction. This is a schematic view of the electrode body of Figure 3 as seen from the right side. (a) is a schematic cross-sectional view of the electrode body constituting the non-aqueous electrolyte secondary battery of the embodiment, perpendicular to the winding axis direction, (b) is an enlarged view of part A of (a), and (c) is an enlarged view of part B of (a). (a) is a view of the unfolded state of the positive electrode constituting the non-aqueous electrolyte secondary battery of the embodiment as seen from the outside of the winding, which is one side in the thickness direction, and (b) is a view as seen from the inside of the winding, which is the other side in the thickness direction. This is an enlarged perspective view of part C of Figure 6. (a) is a view of the unfolded state of the negative electrode constituting the non-aqueous electrolyte secondary battery of the embodiment as seen from the outside of the winding, which is one side in the thickness direction, and (b) is a view as seen from the inside of the winding, which is the other side in the thickness direction. (a) is a schematic cross-sectional view perpendicular to the winding axis direction of the electrode body constituting the comparative example non-aqueous electrolyte secondary battery, (b) is an enlarged view of part D in (a), and (c) is an enlarged view of part E in (a). (a) is a view of the unfolded state of the positive electrode constituting the comparative example non-aqueous electrolyte secondary battery, seen from the outside of the winding, which is one side in the thickness direction, and (b) is a view of the inside of the winding, which is the other side in the thickness direction. (a) is a view of the unfolded state of the negative electrode constituting the comparative example non-aqueous electrolyte secondary battery, seen from the outside of the winding, which is one side in the thickness direction, and (b) is a view of the inside of the winding, which is the other side in the thickness direction.

[0010] The embodiments of this disclosure will be described below with reference to the drawings. The embodiments described below are not limiting to this disclosure, and configurations formed by selectively combining multiple examples are also included in this disclosure.

[0011] "Overall Configuration of Non-Aqueous Electrolyte Secondary Battery" Figure 1 is a perspective view showing the schematic shape of a non-aqueous electrolyte secondary battery 10 according to an embodiment. Figure 2 is a schematic partial cross-sectional view of the non-aqueous electrolyte secondary battery 10 when it is cut in a cross section that passes through the positive electrode tab 22 and includes the thickness direction of the electrode body 60 and the winding axis O1 direction. Hereinafter, the non-aqueous electrolyte secondary battery 10 will be referred to as secondary battery 10.

[0012] The secondary battery 10 has a thin rectangular parallelepiped shape overall and comprises an electrode body 60, an outer casing 12 that houses the electrode body 60 and a non-aqueous electrolyte, a positive electrode tab 22 and a negative electrode tab 24. The positive electrode tab 22 corresponds to the first electrode tab. The negative electrode tab 24 corresponds to the second electrode tab. In this example, the secondary battery 10 is a lithium-ion secondary battery. The non-aqueous electrolyte secondary battery of this disclosure is not limited to a lithium-ion secondary battery, but may be any non-aqueous electrolyte secondary battery that can take the configuration of this disclosure.

[0013] In the following description and drawings, the X direction indicates the thickness direction of the secondary battery 10, the Y direction indicates the width direction of the secondary battery 10, and the Z direction indicates the height direction of the secondary battery 10. The X, Y, and Z directions are orthogonal to each other. The Z direction corresponds to the winding axis direction of the electrode body 60. In addition, the α direction indicates the longitudinal direction of the positive electrode 30, and the β direction indicates the short direction of the positive electrode 30. The γ direction indicates the longitudinal direction of the negative electrode 40, and the δ direction indicates the short direction of the negative electrode 40. The α and β directions are orthogonal to each other, and the γ and δ directions are also orthogonal to each other.

[0014] The outer casing 12 is a metal laminate resin sheet, formed by folding a film-like laminate sheet 11 containing an adhesive resin layer in half along the bottom portion 17, and a wound electrode body 60 is housed in a cup-shaped housing portion 13.

[0015] The laminate sheet 11 has a metal layer made of, for example, aluminum or an aluminum alloy, and an inner resin layer, which is an adhesive resin layer, is provided on the inner surface when the sheet is folded in half and overlapped. The inner resin layer is made of, for example, polypropylene. The metal layer and the inner resin layer can be bonded together, for example, by carboxylic acid-modified polypropylene, which is polypropylene to which carboxyl groups have been added. The electrode body 60 is then wrapped in the folded laminate sheet 11, and three sides of the outer periphery of the laminate sheet 11 are sealed.

[0016] In the example shown in Figure 1, the outer casing 12 is provided with a top portion 16 on the upper side, a bottom portion 17 on the lower side, a first side portion 18 on the left side, and a second side portion 20 on the right side. The top portion 16 and the first and second side portions 18 and 20 are each portions where the laminate sheets 11 are overlapped, and a sealing portion is formed in each of them. The first and second side portions 18 and 20 are then folded back in the thickness direction of the laminate sheet 11 and overlapped with the side walls of the housing portion 13.

[0017] The top portion 16 is the end of the outer casing 12 opposite to the bottom portion 17, where the longitudinal ends of the laminate sheet 11 overlap, and the positive electrode tab 22 and negative electrode tab 24 are led out. The positive electrode tab 22 is connected to the positive electrode 30 of the electrode body 60. The negative electrode tab 24 is connected to the negative electrode 40 of the electrode body 60. The welding resins 26 and 28, described later, are fixed to the positive electrode tab 22 and the negative electrode tab 24. In the following, the top portion 16 side of the secondary battery 10 may be referred to as the upper side and the bottom portion 17 side as the lower side, but this does not limit the orientation of the secondary battery 10 in use.

[0018] The secondary battery 10, equipped with such an outer casing 12, is electrically connected to an external load by a positive electrode tab 22 and a negative electrode tab 24.

[0019] The bottom portion 17 is the folded portion of the laminate sheet 11 in the outer casing 12. The first side portion 18 and the second side portion 20 are arranged along the Z direction in the overlapping portion of the outer periphery of the folded laminate sheet 11.

[0020] In the top section 16 and each side section 18, 20, the opposing portions of the folded laminate sheet 11 are overlapped so that they are in contact with each other's inner resin layers, and the outer periphery of the two sheet elements 11a and 11b is welded together by heating and pressing. A cup-shaped housing section 13 for housing the electrode body 60 is provided inside the overlapping portion of sheet element 11a. The opening of the housing section 13 is closed by the flat outer section 15 of sheet element 11b.

[0021] The electrode body 60 has a long positive electrode 30 to which a positive electrode tab 22 is connected, and a long negative electrode 40 to which a negative electrode tab 24 is connected. The positive electrode 30 and the negative electrode 40 are wound around each other via a separator 70 to form a wound electrode body, and then the wound electrode body is press-formed into a flat shape. The positive electrode tab 22 is joined to the positive electrode 30 by ultrasonic welding, spot welding, etc. The negative electrode tab 24 is joined to the negative electrode 40 by ultrasonic welding, spot welding, etc. In this example, the positive electrode 30 corresponds to the first electrode, and the negative electrode 40 corresponds to the second electrode.

[0022] As will be described later, the separator 70 has an adhesive layer and is bonded to the positive electrode 30 and the negative electrode 40 by the adhesive layer.

[0023] The positive electrode tab 22 is led out to the outside of the battery via a sealing portion 29 provided at the top of the outer casing 12, forming a positive electrode lead-out portion 22a. The negative electrode tab 24 is led out to the outside of the battery via a sealing portion provided at the top of the outer casing 12, forming a negative electrode lead-out portion 24a. In Figure 1, the positive electrode lead-out portion 22a and the negative electrode lead-out portion 24a are arranged apart from each other in the second direction Y and extend in the third direction Z. Each sealing portion 29 is heat-welded with two sheet elements 11a and 11b sandwiching the positive electrode tab 22 and the negative electrode tab 24, respectively, sealing the space between the sheet elements 11a and 11b. Welding resins 26 and 28 are fixed around each tab 22 and 24. The welding resins 26 and 28 are preferably made of an insulating resin material, such as modified polyolefin, polyester, or polyvinylidene fluoride.

[0024] Furthermore, the laminate sheet 11 may have an outer resin layer on the surface that faces the outside of the metal layer when folded in half and overlapped. The outer resin layer may be made of, for example, nylon. The metal layer and the outer resin layer may be bonded together, for example, with a dry laminating adhesive.

[0025] Non-aqueous electrolytes have ionic conductivity (e.g., lithium ion conductivity). A non-aqueous electrolyte comprises a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte is not limited to a liquid electrolyte (non-aqueous electrolyte solution), but may also be a solid electrolyte using a gel-like polymer or the like. A non-aqueous electrolyte secondary battery is preferably a lithium-ion battery. Examples of electrolyte salts include LiBF. ４ LiPF ６ Lithium salts such as the above are used. Non-aqueous solvents include, for example, esters such as ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), and methyl propionate (MP), as well as ethers, nitriles, amides, and mixed solvents of two or more of these. The non-aqueous solvent may contain halogen-substituted products in which at least some of the hydrogen atoms of these solvents are replaced with halogen atoms such as fluorine.

[0026] Examples of halogen-substituted compounds include fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated linear carbonates, and fluorinated linear carboxylic acid esters such as methyl fluoropropionate (FMP). In terms of suppressing the deterioration of the charge-discharge cycle characteristics of non-aqueous electrolyte secondary batteries or improving the input characteristics, the non-aqueous electrolyte preferably contains 5% by mass or more of FEC relative to the mass of the non-aqueous electrolyte, and more preferably contains 5% to 15% by mass of FEC.

[0027] As solid electrolytes, for example, solid or gel-like polymer electrolytes, inorganic solid electrolytes, etc., are used. Polymer electrolytes include, for example, a lithium salt and a matrix polymer, or a non-aqueous solvent, a lithium salt and a matrix polymer. As matrix polymers, for example, polymer materials that absorb non-aqueous solvents and gel are used. As polymer materials, for example, fluororesins, acrylic resins, polyether resins, etc., are used. As inorganic solid electrolytes, for example, materials known for all-solid-state lithium-ion secondary batteries, etc. (for example, oxide-based solid electrolytes, sulfide-based solid electrolytes, halide-based solid electrolytes, etc.) are used.

[0028] "Configuration of the electrode body and arrangement of electrode tabs" The configuration of the electrode body 60 and the arrangement of the electrode tabs, namely the positive electrode tab 22 and the negative electrode tab 24, on the electrode body 60 will be explained in detail using Figures 2 to 8. Figure 3 is a schematic diagram of the electrode body 60 of the secondary battery 10 in Figure 1, viewed in the thickness direction. Figure 4 is a schematic diagram of the electrode body 60 in Figure 3, viewed from the right side.

[0029] As shown in Figures 3 and 4, the electrode body 60 has a positive electrode 30 positioned at its outermost circumference, and the winding end 33 of the positive electrode 30 is fixed to the outermost circumference 35 of the positive electrode 30 with a winding stopper tape 55 that extends along the Z direction corresponding to the winding axis direction. Furthermore, a bottom tape 57 is attached to the lower end of the electrode body 60 on the bottom portion 17 side (Figure 1), which is the end opposite to the lead-out side of each tab 22, 24, spanning both sides in the thickness direction of the electrode body 60. The winding stopper tape 55 and the bottom tape 58 are insulating adhesive tapes, each having an adhesive layer on one side of the base material layer.

[0030] In the electrode body 60, the separator 70 extends above the upper ends of the positive electrode 30 and the negative electrode, and also extends below the lower ends of the positive electrode 30 and the negative electrode. The bottom tape 57 straddles the vicinity of the lower end of the outermost circumference 35 of the positive electrode 30 at both ends in the thickness direction of the electrode body 60, and is attached to the lower end of the separator 70 that extends below the lower end of the positive electrode 30. In this state, the bottom tape 58 is arranged to include portions facing the positive electrode tab 22 and the negative electrode tab 24 in the Z direction corresponding to the winding axis direction.

[0031] Figure 5(a) is a schematic cross-sectional view perpendicular to the winding axis O1 direction of the electrode body 60 constituting the secondary battery 10. Figure 5(b) is an enlarged view of part A in Figure 5(a), and Figure 5(c) is an enlarged view of part B in Figure 5(a).

[0032] As shown in Figures 2 and 5, the electrode body 60 consists of a long positive electrode 30 and a long negative electrode 40, which are wound in a flattened shape via a separator 70. In Figure 5, the positive electrode 30 is shown by the shape formed by the connection of thick and thin solid lines. The negative electrode 40 is shown by the dashed line. The separator is not shown in Figure 5.

[0033] Furthermore, in Figure 5, the thick line portion of the positive electrode 30 indicates the portion where the positive electrode mixture layer 32 (Figure 6) is formed on at least one side of the positive electrode core 31, while the thin line portion indicates the portion where the positive electrode mixture layer is not formed on both sides of the positive electrode core 31. The positive electrode core 31 is the first core, and the positive electrode mixture layer 32 is the first mixture layer. On the inner circumference side of the electrode body 60, the negative electrode 40 extends from the winding start end of the positive electrode 30 toward the winding start side. On the other hand, on the outer circumference side of the electrode body 60, the positive electrode 30 extends from the winding end end 43 of the negative electrode 40 toward the winding end side. The outermost circumference of the separator is positioned between the outermost circumference of the positive electrode 30 and the outermost circumference of the negative electrode 40, and the winding end of the separator is positioned between the winding end end 43 of the negative electrode 40 and the winding end end 33 of the positive electrode 30. In this manner, the positive electrode 30 is positioned on the outermost periphery of the electrode body 60, and the winding end 33 of the positive electrode 30 is fixed by a winding stopper tape 55 that is attached to the outermost periphery of the positive electrode 30 so as to straddle the winding end 33 of the positive electrode 30.

[0034] When the outermost circumference 35 of the positive electrode 30 is divided into two parts by a plane Q1 perpendicular to the thickness direction and passing through the winding axis O1, on the side of the outer casing flat portion 15 (Figure 2) and the side of the bottom end 13a of the housing portion 13, the positive electrode tab 22 is attached to the side of the outer casing flat portion 15. More specifically, as shown in Figure 5, when the electrode 60 is cut in a cross section perpendicular to the winding axis O1, the cross-sectional shape of the electrode 60 includes two curved portions R1 and R2 at both ends in the Y direction corresponding to the width direction of the electrode 60, and two flat portions T1 and T2 that connect one end of the two curved portions R1 and R2 to each other and the other end to each other, respectively. The outer surfaces of each flat portion T1 and T2 are substantially parallel to each other. At this time, the positive electrode tab 22 is joined to the core exposed portion 31a provided on the part of the outermost circumference 35 of the positive electrode 30 that constitutes one of the flat portions T1 on the side of the outer casing flat portion 15. The core exposed portion 31a is the part of the positive electrode core to which the positive electrode mixture layer is not provided. In this way, the positive electrode tab 22 is attached to the outermost circumference 35 of the positive electrode 30. Furthermore, as will be described later, the core exposed portion 31a to which the positive electrode tab 22 is attached is surrounded on three sides by the positive electrode mixture layer 32 (Figure 6) on the inner surface of the winding of the positive electrode 30. In addition, the core exposed portion 31a to which the positive electrode tab 22 is attached is located within one turn from the winding end 34 toward the winding start side of the inner positive electrode mixture layer 32, which is located closest to the winding end, to the winding start side. The core exposed portion 31a is not limited to being attached to the outermost circumference 35 of the positive electrode 30, and only needs to be located within one turn from the winding end 34 toward the winding start side of the inner positive electrode mixture layer 32.

[0035] Furthermore, the core exposed portion 31a of the positive electrode 30 and the portion of the positive electrode tab 22 that overlaps with the core exposed portion 31a are covered with insulating tape 50. The insulating tape 50 is made of an insulating material such as polyimide. A portion of the insulating tape 50 may be attached to the surface of the positive electrode mixture layer. The positive electrode tab 22 may be joined to the core exposed portion of the positive electrode 30 that is located on the outer side of the flat portion T1 on the outer casing flat portion 15 side. In this case as well, the positive electrode tab 22 is attached to the portion surrounded on three sides by the positive electrode mixture layer, and is therefore attached to the portion of the positive electrode 30 that is sandwiched between two positive electrode mixture layers that are separated in the winding direction.

[0036] On the other hand, the negative electrode tab 24 is located on the intermediate circumference 45 between the innermost and outermost circumferences of the negative electrode 40, and is attached to the flat portion 15 of the outer casing when the electrode body 60 is divided into two parts by a plane Q1 perpendicular to the thickness direction.

[0037] More specifically, in the cross-sectional shape obtained by cutting the electrode body 60 in a cross-section perpendicular to the winding axis O1 direction, the negative electrode tab 24 is joined to the inside of the winding of the core body exposed portion 41a, which is located on the curved portion R2 side of the intermediate circumference 45 of the negative electrode 40 and constitutes the flat portion T1 on the outer casing flat portion 15 side. As a result, the negative electrode tab 24 is located on the same half side (upper side in Figure 5) that is divided in the center of the thickness direction of the electrode body 60, which coincides with the first direction X in Figure 3, and is positioned closer to the center of the thickness direction of the electrode body 60 (plane Q1 side) than the positive electrode tab 22.

[0038] The mounting portion of the negative electrode tab 24 on the negative electrode 40 is preferably positioned on the center side in the thickness direction of the electrode body 60, from a position 2 / 3 of the thickness from the innermost to the outermost circumference of the flat portion T1 on the outer casing flat portion 15 side. With this preferred configuration, when the separator is bonded to the positive electrode 30 and the negative electrode 40, poor adhesion of the separator due to a decrease in the flatness of the outer surface of the flat portion T1 is suppressed. As a result, peeling of the separator due to impact when the secondary battery 10 is dropped can be suppressed, and the voltage drop can be further suppressed.

[0039] Furthermore, the core exposed portion 41a of the negative electrode 40 and the portion of the negative electrode tab 24 that overlaps with the core exposed portion 41a are covered with insulating tape 50. A portion of the insulating tape 50 may be attached to the surface of the negative electrode mixture layer. The negative electrode tab 24 may be joined to the outer side of the core exposed portion of the negative electrode 40, which is provided in the portion that constitutes the flat portion T1 on the outer casing flat portion 15 side.

[0040] Figure 6(a) shows the unfolded state of the positive electrode 30 as viewed from the outer side of the winding, which is one side in the thickness direction, and Figure 6(b) shows the view as viewed from the inner side of the winding, which is the other side in the thickness direction. Figure 7 is an enlarged perspective view of section C in Figure 6.

[0041] In FIGS. 6(a) and 6(b), the vertical direction of the positive electrode 30 is reversed. In FIG. 6, the left end of the positive electrode 30 on the paper surface is the winding start end. In FIG. 6, the length of the positive electrode 30 in the longitudinal direction of the electrode plate is shown shorter than the actual length.

[0042] The positive electrode 30 includes a positive electrode core 31 and positive electrode mixture layers 32 provided on both surfaces of the positive electrode core 31. In FIG. 6, the positive electrode core 31 is indicated by a coarse sand-textured portion, and the positive electrode mixture layer 32 is indicated by a fine sand-textured portion.

[0043] For the positive electrode core 31, a foil of a metal stable in the potential range of the positive electrode 30, such as aluminum or an aluminum alloy, or a film having the metal disposed on the surface layer can be used. A suitable positive electrode core 31 is a metal foil containing aluminum or an aluminum alloy as a main component. The thickness of the positive electrode core 31 is, for example, 10 μm to 30 μm.

[0044] The positive electrode mixture layer 32 contains a positive electrode active material, a conductive agent such as acetylene black, and a binder such as polyvinylidene fluoride (PVdF), and is preferably formed on both surfaces of the positive electrode core. The thickness of the positive electrode mixture layer 32 on one side is, for example, 40 μm or more and 100 μm or less. For the positive electrode active material, for example, a lithium transition metal composite oxide containing Ni, Co, Mn, Al or the like is used.

[0045] The positive electrode 30 is produced by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, and a solvent such as N-methyl-2-pyrrolidone (NMP) onto both surfaces of the positive electrode core 31, followed by drying and rolling.

[0046] Examples of the positive electrode active material include lithium-containing transition metal oxides containing transition metal elements such as Co, Mn, and Ni. The lithium-containing transition metal oxide is not particularly limited, and has the general formula Li １＋ｘ MO ２ (wherein -0.2 < x ≤ 0.2, and M contains at least one of Ni, Co, Mn, and Al), and is preferably a composite oxide represented by the formula.

[0047] The positive electrode compound layer 32 provided on the inner side of the positive electrode core 31 shown in Figure 6(b) includes an extension 36 that extends toward the end of the winding than the end of the positive electrode compound layer 32 provided on the outer side of the positive electrode core 31 shown in Figure 6(a). The positive electrode tab 22 is attached to the core exposed portion 31a, which is sandwiched between the two formed portions A1 and A2 of the positive electrode compound layer 32 in the longitudinal direction of the positive electrode 30, which is the winding direction, by joining them by ultrasonic welding or the like. The core exposed portion 31a is the part where the surface of the metal constituting the positive electrode core 31 is not covered by the positive electrode compound layer 32 and is exposed. The core exposed portion 31a is formed only on a part of the positive electrode 30 including one side end (upper end in Figure 6(a), lower end in Figure 4(b)) in the winding axis O1 direction of the electrode body 60.

[0048] The positive electrode tab 22 is a strip-shaped conductive member. The constituent material of the positive electrode tab 22 is not particularly limited, but it is preferable that the positive electrode tab 22 be made of a metal mainly composed of aluminum.

[0049] As described above, the positive electrode tab 22 is attached to the core body exposed portion 31a sandwiched between the forming portions A1 and A2 of the positive electrode mixture layer 32, which are separated in the winding direction of the positive electrode 30. Therefore, the reduction in the flatness of the outer surface of the flat portion T1 on the outer surface of the outer casing flat portion 15 side, which is a surface perpendicular to the thickness direction of the outer surface of the electrode body 60 due to the positive electrode tab 22, can be suppressed by the thickness of the positive electrode mixture layer 32. As a result, poor adhesion of the separator 70, which will be described later, can be suppressed. As a result, voltage drop due to impact from dropping, which will be described later, can be suppressed in the secondary battery 10. Furthermore, it becomes possible to increase the capacity of the secondary battery 10.

[0050] Furthermore, in this example, as shown in Figure 7, the positive electrode tab 22 is attached to the exposed core portion 31a, which is surrounded on three sides by the positive electrode mixture layer 32. As a result, the rigidity around the attachment portion of the positive electrode tab 22 in the positive electrode 30 can be increased, thereby further improving the flatness of the outer surface of the flat portion T1 on the outer casing flat portion 15 side located near the positive electrode tab 22. This further suppresses adhesion defects of the separator 70. Moreover, it becomes possible to further increase the capacity of the secondary battery 10.

[0051] Furthermore, as shown in Figure 6, a positive electrode core exposed portion 31b, to which a positive electrode tab is not attached, is formed only on a part of the short side of the positive electrode 30, along with the core exposed portion 31a, and this core exposed portion 31b is covered with insulating tape 50. The core exposed portion 31b to which a positive electrode tab is not attached is provided in the formed state of the electrode body 60 to prevent the positive electrode mixture layer 32 from facing the core exposed portion or the portion facing the negative electrode tab 24 provided on both sides of the negative electrode 40, described later, via the separator 70. This makes it possible to suppress Li deposition in the negative electrode 40 during charging.

[0052] Figure 8(a) shows the unfolded state of the negative electrode 40 as viewed from the outside of the winding, which is one side in the thickness direction, and Figure 8(b) shows the view from the inside of the winding, which is the other side in the thickness direction. In Figure 8(a) and Figure 8(b), the vertical direction of the negative electrode 40 is reversed. In Figure 8, the left edge of the negative electrode 40 on the paper is the winding start end. In Figure 8, the longitudinal length of the negative electrode 40 is shown to be shorter than the actual length.

[0053] The negative electrode 40 comprises a negative electrode core 41 and a negative electrode mixture layer 42 provided on both sides of the negative electrode core 41. In Figure 8, the negative electrode core 41 is shown as a coarse sandy area, and the negative electrode mixture layer 42 is shown as a fine sandy area.

[0054] The negative electrode core 41 can be made of a metal foil that is stable in the potential range of the negative electrode 40, such as copper or a copper alloy, or a film with the metal arranged on its surface. The negative electrode mixture layer 42 contains a negative electrode active material and a binder such as styrene-butadiene rubber (SBR). The thickness of the negative electrode mixture layer 42 is, for example, 40 μm to 100 μm on one side. For the negative electrode active material, for example, graphite or a Si-containing material can be used.

[0055] The negative electrode 40 is manufactured by, for example, applying a negative electrode mixture slurry containing a negative electrode active material, a binder, and water to both sides of the negative electrode core 41, followed by drying and rolling.

[0056] The negative electrode active material is not particularly limited as long as it can reversibly intercept and release lithium ions. For example, carbon materials such as natural graphite and artificial graphite, metals that alloy with lithium such as Si and Sn, or alloys and composite oxides containing these can be used.

[0057] The negative electrode compound layer 42 provided on the outer side of the negative electrode core body 41 shown in Figure 8(a) extends towards the winding start side beyond the winding start end of the negative electrode compound layer 42 provided on the inner side of the negative electrode core body 41 shown in Figure 8(b). The negative electrode tab 24 is joined to the core body exposed portion 41a, sandwiched between two longitudinally separated negative electrode compound layer 42 formation portions B1 and B2, on the inner side of the middle portion in the longitudinal direction of the winding direction of the negative electrode 40, by ultrasonic welding or the like. In this way, the negative electrode tab 24 is attached to the core body exposed portion 41a. At this time, the core body exposed portion 41a is surrounded on three sides by the negative electrode compound layer 42, similar to the core body exposed portion 31a. This prevents the deformation of the negative electrode 40 at the attachment portion of the negative electrode tab 24 from affecting the flatness of the separator 70 when the secondary battery is dropped and impacted, and further suppresses the voltage drop. Furthermore, it becomes possible to further increase the capacity of the secondary battery 10.

[0058] The negative electrode tab 24 is a strip-shaped conductive member. The constituent material of the negative electrode tab 24 is not particularly limited. Preferably, the negative electrode tab 24 is made of a metal mainly composed of nickel or copper, or a metal containing both nickel and copper.

[0059] The separator 70 has adhesive layers on both sides of the base layer. The base layer is made of a porous sheet having ion permeability and insulating properties. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. The material of the base layer is preferably an olefin resin such as polyethylene or polypropylene.

[0060] The adhesive layer includes, for example, an adhesive layer resin such as polyvinylidene fluoride (PVdF), and is provided by applying the adhesive layer resin to both sides of the substrate layer. The adhesive layer resin is not limited to PVdF, and can also be other fluororesins such as polytetrafluoroethylene (PTFE), acrylic resins, urethane resins, ethylene vinyl acetate resins, epoxy resins, etc. The separator 70 is, for example, housed in the outer casing 12 with the electrode body 60 formed, and the entire battery is pressed at a high temperature such as 90°C, thereby being bonded to the positive electrode 30 and the negative electrode 40 by the adhesive layer.

[0061] In the secondary battery 10 described above, the separator 70 is bonded to the positive electrode 30 and the negative electrode 40. Furthermore, the positive electrode tab 22, which is positioned near the outer circumference of the electrode body 60, is attached to the exposed core portion 31a sandwiched between two positive electrode mixture layers 32 that are separated in the winding direction of the positive electrode 30. This allows the thickness of the positive electrode mixture layers 32 to suppress the reduction in the flatness of the outer surface of the flat portion T1, which is a surface perpendicular to the thickness direction of the outer surface of the electrode body 60, caused by the positive electrode tab 22. As a result, peeling of the separator 70 can be suppressed while preventing poor adhesion of the separator 70.

[0062] Furthermore, the lower end of the separator 70 is secured by the bottom tape 57 attached to the lower end of the electrode body 60 on the bottom portion 17 side (Figure 1). This further suppresses the curling of the separator 70. Therefore, in the secondary battery 10, when the positive electrode tab 22 is positioned near the outer circumference of the electrode body 60, the curling of the separator 70 due to impact from dropping can be suppressed, thereby suppressing voltage drop.

[0063] Furthermore, in this example, the bottom tape 57 is arranged to include portions facing the positive electrode tab 22 and the negative electrode tab 24 in the Z direction corresponding to the winding axis direction. This further suppresses the separation 70 from being peeled off by vibrations in the winding axis direction of each tab 22, 24 when the secondary battery 10 is dropped and subjected to impact. As a result, the voltage drop of the secondary battery 10 can be further suppressed.

[0064] Furthermore, in this example, the positive electrode tab 22 is attached to the outermost periphery 35 of the positive electrode 30, on the side of the flat portion 15 of the outer casing. As a result, as shown in Figure 2, within the outer casing 12, the portion of the positive electrode tab 22 that leads out from the electrode body 60 towards the sealing portion 29 is not significantly bent towards the flat portion 15 of the outer casing, but can extend almost along the Z direction toward the sealing portion 29. Therefore, the significantly bent portion of the positive electrode tab 22 does not ride up onto the end of the separator on the top portion 16 side. Consequently, even if the outer casing 12 is dropped with its lead portions 22a and 24a facing downwards, and an impact occurs that applies external force from the lead side of the positive electrode tab 22 to the electrode body 60 side, it is possible to suppress the positive electrode tab 22 from being strongly pressed against the negative electrode via the separator. This also helps to suppress the voltage drop of the secondary battery 10.

[0065] Furthermore, the negative electrode tab 24 is attached to the intermediate circumference 45 (Figure 5) between the innermost and outermost circumferences of the negative electrode 40. As a result, the mounting position of the negative electrode tab 24 on the negative electrode 40 is closer to the center in the longitudinal direction of the negative electrode 40 compared to when the negative electrode tab 24 is attached to the outermost circumference of the negative electrode 40. Therefore, the current collection efficiency of the negative electrode 40 through the negative electrode tab 24 is improved, the electrical resistance of the negative electrode 40 can be reduced, and the internal resistance of the secondary battery 10 can be reduced.

[0066] Figure 9(a) is a schematic cross-sectional view of the electrode body 60a constituting the comparative secondary battery, perpendicular to the winding axis O1 direction. Figure 9(b) is an enlarged view of section D in Figure 9(a), and Figure 9(c) is an enlarged view of section E in Figure 9(a). Figure 10(a) is a view of the unfolded state of the positive electrode 30a constituting the comparative secondary battery, seen from the outside of the winding, which is one side in the thickness direction, and Figure 10(b) is a view of the inside of the winding, which is the other side in the thickness direction. Figure 11(a) is a view of the unfolded state of the negative electrode 40a constituting the comparative secondary battery, seen from the outside of the winding, which is one side in the thickness direction, and Figure 11(b) is a view of the inside of the winding, which is the other side in the thickness direction.

[0067] As shown in Figures 9 to 11, in the comparative secondary battery, unlike the secondary battery 10 of the embodiment shown in Figures 1 to 8, the negative electrode tab 24 is arranged on the outermost periphery of the negative electrode 40a, substantially aligned with the positive electrode tab 22 in the Y direction.

[0068] Furthermore, as shown in Figure 10, the positive electrode tab 22 is joined to the inner surface of the positive electrode core 31, which is located on the winding end side of the winding end end 34 of the positive electrode mixture layer 32, on the winding end side of the winding end end of the positive electrode 30a. For this reason, the flatness of the separator 70 placed near the positive electrode tab 22 is reduced by the thickness of the positive electrode tab 22, making it easier for poor adhesion of the separator 70 to occur.

[0069] Furthermore, as shown in Figure 11, the negative electrode tab 24 is joined to the inner surface of the negative electrode core body 41, which is located on the winding side of the winding end end 44 of the negative electrode mixture layer 42, at the winding end end of the negative electrode 40. For this reason, even the separator 70 placed near the negative electrode tab 24 will have reduced flatness due to the thickness of the negative electrode tab 24, making it easier for poor adhesion of the separator 70 to occur.

[0070] In such comparative examples, as described above, poor adhesion of the separator 70 is more likely to occur, which makes it easier for the separator 70 to peel off when the secondary battery is dropped and impacted, leading to a voltage drop.

[0071] The present disclosure will be further illustrated below with reference to examples, but the present disclosure is not limited to these examples.

[0072] <Example 1> [Fabrication of the positive electrode] Lithium cobalt oxide (LiCoO) as the positive electrode active material ２ A positive electrode mixture slurry was prepared by mixing carbon black as a conductive agent and polyvinylidene fluoride (PVdF) as a binder in a mass ratio of 97.6:1.2:1.2, and using N-methyl-2-pyrrolidone (NMP) as a dispersion medium. Next, the positive electrode mixture slurry was applied to both sides of a positive electrode core made of aluminum foil, and after drying and compressing the coating film, the positive electrode core was cut to a predetermined electrode size to obtain a positive electrode in which a positive electrode mixture layer was formed on the positive electrode core, as shown in Figure 6. Furthermore, an aluminum positive electrode tab was welded to the exposed core portion of the inner surface of the winding at one longitudinal end of the positive electrode, which is the winding end end, where three sides are surrounded by the positive electrode mixture layer.

[0073] [Fabrication of the negative electrode] Graphite was used as the negative electrode active material. This negative electrode active material, sodium salt of carboxymethylcellulose (CMC), and a dispersion of styrene-butadiene rubber (SBR) were mixed in a solid content mass ratio of 97.6:1.2:1.2, and water was used as the dispersion medium to prepare a negative electrode mixture slurry. Next, the negative electrode mixture slurry was applied to both sides of a negative electrode core made of copper foil, the coating was dried and rolled, and then the negative electrode core was cut to a predetermined electrode size to obtain a negative electrode in which a negative electrode mixture layer was formed on the negative electrode core, as shown in Figure 8. A nickel negative electrode tab was welded to the exposed core portion of the winding inner surface in the longitudinal middle of the negative electrode, where three sides were surrounded by the negative electrode mixture layer.

[0074] [Preparation of the separator] As a separator, a 20 μm thick separator was prepared by coating both sides of a microporous polyethylene film, which is a 16 μm thick base layer, with polyvinylidene fluoride (PVdF) to a thickness of 2 μm on each side as an adhesive resin.

[0075] [Preparation of Non-Aqueous Electrolyte] Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) are mixed in a volume ratio of 30:70 (at a temperature of 25°C) to form a solvent to which lithium hexafluoride phosphate (LiPF) is added. ６ The electrolyte was prepared by dissolving ) at a concentration of 1.2 mol / L.

[0076] [Fabrication of Secondary Battery] The positive and negative electrodes were wound in a spiral shape with a separator in between, and then the wound body was pressed flat to obtain an electrode body. A bottom tape was attached to the lower end of the obtained electrode body, as shown in Figures 3 and 4. In this case, the bottom tape was positioned to include the positive electrode tab and the negative electrode tab, and the portion facing the winding axis of the electrode body. A laminate sheet was processed to form an outer casing, and the electrode body and the above-mentioned non-aqueous electrolyte were placed inside the casing in an inert atmosphere. After that, it was pressed at a pressure of 1 MPa at 90°C to bond the separator between the positive and negative electrodes, and then the opening of the casing was sealed to produce a secondary battery of Example 1 with dimensions of 69 mm in length, 56 mm in width, 4.9 mm in thickness, and a rated capacity of 3150 mAh.

[0077] <Example 2> When attaching the bottom tape to the lower end of the electrode body, the bottom tape was positioned so that it included only the negative electrode tab and the portion facing the electrode body in a direction parallel to the winding axis direction. Otherwise, the secondary battery was manufactured in the same manner as in Example 1.

[0078] <Example 3> When attaching the bottom tape to the lower end of the electrode body, the bottom tape was positioned so that it did not face either the positive electrode tab or the negative electrode tab in the direction of the winding axis of the electrode body. Otherwise, the secondary battery was manufactured in the same manner as in Example 1.

[0079] <Comparative Example 1> The separator consisted only of a base layer, and no adhesive resin was applied. The placement of the tabs for the positive and negative electrodes was the same as in the comparative example shown in Figures 9 to 11. No bottom tape was attached to the lower end of the electrode body. Otherwise, a secondary battery was manufactured in the same manner as in Example 1.

[0080] <Comparative Example 2> The separator consisted only of a base layer, and no adhesive resin was applied. Bottom tape was not attached to the lower end of the electrode body. Otherwise, the secondary battery was manufactured in the same manner as in Example 1.

[0081] <Comparative Example 3> The placement of tabs on the positive and negative electrodes was the same as in the comparative examples shown in Figures 9 to 11. Bottom tape was not attached to the lower end of the electrode body. Otherwise, the secondary battery was manufactured in the same manner as in Example 1.

[0082] <Comparative Example 4> The separator consisted only of a substrate layer, and no adhesive resin was applied. The placement of the tabs relative to the positive and negative electrodes was the same as in the comparative examples shown in Figures 9 to 11. Otherwise, a secondary battery was manufactured in the same manner as in Example 1.

[0083] <Comparative Example 5> Bottom tape was not attached to the lower end of the electrode body. Otherwise, the secondary battery was manufactured in the same manner as in Example 1.

[0084] <Comparative Example 6> The separator consisted only of a substrate layer, and no adhesive resin was applied. Otherwise, the secondary battery was manufactured in the same manner as in Example 1.

[0085] <Comparative Example 7> The placement of the tabs on the positive and negative electrodes was the same as in the comparative examples shown in Figures 9 to 11. Otherwise, the secondary battery was manufactured in the same manner as in Example 1.

[0086] [Drop Test] To simulate a product containing a secondary battery, test specimens were prepared by sandwiching each of the 10 types of secondary batteries from Examples 1-3 and Comparative Examples 1-7 between two acrylic resin plates. The test specimens were dropped from a height of 1 m with the positive electrode tab 22 and negative electrode tab 24 lead-outs facing upwards, and then dropped from a height of 1 m with the positive electrode tab 22 and negative electrode tab 24 lead-outs facing downwards. This drop test was repeated 5 times. Drop tests were performed on 10 test specimens of each secondary battery, and the presence or absence of voltage drop after the drop test was checked.

[0087] <Test Results> Table 1 shows the results of the drop test for the secondary batteries related to Examples 1-3 and Comparative Examples 1-7.

[0088]

[0089] Table 1 shows that for each of the 10 test samples (N=10), it was confirmed whether a voltage drop occurred at least once in a total of 10 drop tests. In Table 1, for example, "10 / 10 No voltage drop" in the column for Example 1 indicates that no voltage drop was observed in any of the 10 test samples. "2 / 10 Voltage drop observed" in the column for Example 2 indicates that a voltage drop was observed in 2 out of the 10 test samples.

[0090] Furthermore, in the "Positive electrode, negative electrode shape, tab arrangement" column, "Same as the embodiment" indicates that the configuration is the same as the embodiment shown in Figures 5 to 8, and "Same as the comparative example" indicates that the configuration is the same as the comparative example shown in Figures 9 to 11.

[0091] Furthermore, in the "Bottom Tape" column, "Opposite to positive and negative electrode tabs" indicates that the bottom tape is positioned to include portions facing the positive and negative electrode tabs in the direction of the winding axis of the electrode body, while "Opposite to negative electrode tab" indicates that the bottom tape is positioned only in the area extending from the center of the electrode body in the Y direction in Figure 3 to the end of the negative electrode tab. "Not opposed" indicates that the bottom tape is positioned only in the center of the electrode body in the Y direction in Figure 3, and that the bottom tape does not include portions facing the positive and negative electrode tabs in the direction of the winding axis of the electrode body.

[0092] As can be seen from the results shown in Table 1, no voltage drop was observed in any of the test samples in Example 1. In Examples 2 and 3, the number of test samples that showed a voltage drop was small, at two or four. This is thought to be because, in Examples 1 to 3, there was no or very little adhesion failure of the separator inside the test samples, which suppressed the peeling of the separator. Therefore, even when an external force was applied due to a drop impact, a short circuit where the positive and negative electrodes came into contact was unlikely to occur. Thus, it was confirmed that safety in the event of a drop impact could be improved in Examples 1 to 3.

[0093] Furthermore, as in Example 2, when the bottom tape was positioned so as to face the negative electrode tab and the electrode body in the winding axis direction, the number of test samples exhibiting voltage drop decreased from four to two compared to Example 3. This is thought to be because, when the secondary battery is dropped and impact occurs, vibrations in the winding axis direction of the negative electrode tab make it easier to suppress the separation from peeling off.

[0094] Furthermore, as in Example 1, when the bottom tape was positioned so that the positive electrode tab and negative electrode tab faced the electrode body in a direction parallel to the winding axis, no voltage drop occurred in any of the tests. This is thought to be because, when the secondary battery is dropped and impact occurs, vibrations in the winding axis direction of the positive electrode tab and negative electrode tab make it easier to suppress the separation from being peeled off.

[0095] On the other hand, in Comparative Examples 1 and 2, a voltage drop was observed in all test samples. This is thought to be because, in Comparative Examples 1 and 2, an adhesive layer was not provided on the separator, and bottom tape was not attached to the lower end of the electrode body, resulting in greater peeling of the separator.

[0096] Furthermore, in Comparative Examples 3 to 7, a voltage drop was observed in 8 to 9 test samples. This is thought to be due to the absence of a bottom tape in Comparative Example 3 and the fact that the positive electrode tab was not positioned to be sandwiched between the positive electrode mixture layers in the winding direction. In Comparative Example 4, the above reasons are thought to be due to the absence of an adhesive layer on the separator and the fact that the positive electrode tab was not positioned to be sandwiched between the positive electrode mixture layers in the winding direction.

[0097] Furthermore, in Comparative Examples 5 to 7, the above reasons are thought to be due to the absence of one or more of the following: the absence of a bottom tape, the absence of an adhesive layer on the separator, or the absence of the positive electrode tab being positioned so that it is sandwiched between the positive electrode mixture layers in the winding direction.

[0098] In the above embodiment, the positive electrode tab, which is the first electrode tab, was described as being attached to the core exposed portion of the positive electrode, which is the first electrode, and which is surrounded on three sides by the positive electrode mixture layer, which is the first mixture layer. On the other hand, the first electrode tab may be attached to the core exposed portion that extends over the entire width direction perpendicular to the longitudinal direction of the first electrode, and the core exposed portion may be sandwiched between two first mixture layers that are separated in the winding direction of the first electrode.

[0099] Furthermore, in the above embodiment, the case described was that the first electrode is a positive electrode to which a positive electrode tab, which is the first electrode tab, is connected, and the second electrode is a negative electrode to which a negative electrode tab, which is the second electrode tab, is connected. On the other hand, the configuration may be such that the first electrode is a negative electrode to which a negative electrode tab, which is the first electrode tab, is connected, and the second electrode is a positive electrode to which a positive electrode tab, which is the second electrode tab, is connected. In this case, the first core body is a negative electrode core body, and the first mixture layer is a negative electrode mixture layer.

[0100] The present disclosure is further described by the following embodiments. Configuration 1: A flat electrode body is wound with a separator in between, comprising a first electrode to which a first electrode tab is connected and a second electrode to which a second electrode tab is connected, the first electrode tab and the second electrode tab are led out from the same end in the winding axis direction of the electrode body, the separator has an adhesive layer and is bonded to the first electrode and the second electrode by the adhesive layer, the first electrode has a first core body and a first compound layer provided on the first core body, the first electrode tab is attached to a core body exposed portion of the first core body where the first compound layer is not provided, located within one turn from the winding end of the first compound layer toward the winding start side, and is sandwiched between two first compound layers that are separated from each other in the winding direction of the first electrode, the second electrode tab is located on the same half side divided in the thickness direction of the electrode body by the center of the first electrode tab and the electrode body, and is positioned closer to the center in the thickness direction of the electrode body than the first electrode tab, Furthermore, tape is attached across both sides in the thickness direction of the electrode body to the end of the electrode body opposite to the lead-out side of the first electrode tab and the second electrode tab. Configuration 2: The non-aqueous electrolyte secondary battery according to Configuration 1, wherein the cross-sectional shape of the electrode body perpendicular to the winding axis direction includes two curved portions at both ends in the width direction of the electrode body and two flat portions connecting one end of the two curved portions and the other end of the two curved portions, the first electrode tab and the second electrode tab are arranged in one of the flat portions, and the second electrode tab is positioned in the thickness direction of the electrode body towards the center, from a position that is 2 / 3 of the thickness of the flat portion of the electrode body, moving from the innermost to the outermost circumference. Configuration 3: The non-aqueous electrolyte secondary battery according to Configuration 1 or Configuration 2, wherein the first mixture layer is arranged on the side of the exposed core body opposite to the lead-out side of the first electrode tab. Configuration 4: A non-aqueous electrolyte secondary battery according to any one of Configurations 1 to 3, wherein the tape is arranged to include portions of at least one of the electrode tabs, the first electrode tab and the second electrode tab, that face each other in the winding axis direction.

[0101] 10 Non-aqueous electrolyte secondary battery (secondary battery), 11 Laminate sheet, 12 Outer casing, 13 Housing section, 15 Flat section of outer casing, 16 Top section, 17 Bottom section, 18 First side section, 20 Second side section, 22 Positive electrode tab, 24 Negative electrode tab, 26, 28 Welding resin, 29 Sealing section, 30, 30a Positive electrode, 31 Positive electrode core, 32 Positive electrode mixture layer, 33, 34 End of winding, 35 Outermost part, 36 Extension section, 40, 40a Negative electrode, 41 Negative electrode core, 42 Negative electrode mixture layer, 43, 44 End of winding, 45 Intermediate circumference, 50, 51 Insulating tape, 55 Winding stopper tape, 57 Bottom tape, 60, 60a Electrode body, 70 Separator, R1, R2 Curved section, T1, T2 Flat section.

Claims

1. The electrode body comprises a flat electrode body wound with a separator in between, the first electrode to which a first electrode tab is connected and the second electrode to which a second electrode tab is connected, the first electrode tab and the second electrode tab are led out from the same end in the winding axis direction of the electrode body, the separator has an adhesive layer and is bonded to the first electrode and the second electrode by the adhesive layer, the first electrode has a first core body and a first compounding layer provided on the first core body, the first electrode tab is attached to a core body exposed portion of the first core body where the first compounding layer is not provided, located within one turn from the winding end of the first compounding layer toward the winding start side, and is sandwiched between two first compounding layers that are separated from each other in the winding direction of the first electrode, the second electrode tab is located on the same half side divided in the thickness direction of the electrode body by the center of the first electrode tab and the electrode body, and is positioned closer to the center in the thickness direction of the electrode body than the first electrode tab, Furthermore, a tape is attached across both sides in the thickness direction of the electrode body to the ends of the electrode body opposite to the lead-out sides of the first electrode tab and the second electrode tab.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the cross-sectional shape of the electrode body perpendicular to the winding axis direction includes two curved portions at both ends in the width direction of the electrode body and two flat portions connecting one end of the two curved portions and the other end of the two curved portions, the first electrode tab and the second electrode tab are arranged in one of the flat portions, and the second electrode tab is positioned in the one flat portion toward the center in the thickness direction of the electrode body from a position that is 2 / 3 of the thickness of the one flat portion toward the outermost circumference toward the outermost circumference.

3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the first mixture layer is disposed on the side opposite to the lead-out side of the first electrode tab in the exposed core portion.

4. The non-aqueous electrolyte secondary battery according to claim 1, wherein the tape is arranged to include portions of at least one of the electrode tabs, the first electrode tab and the second electrode tab, that face each other in the winding axis direction.

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