Secondary battery and method for manufacturing the same

Abstract

The present invention provides a secondary battery that can not only absorb impact more fully, but also can more fully reduce the risk of electrodes being exposed in the secondary battery and the risk of a separator being trapped between components of an outer casing. The present invention relates to a secondary battery (100A), comprising a wound electrode assembly (5) wound with a positive electrode (1), a negative electrode (2) and a separator (3) arranged between the positive electrode and the negative electrode, and a collector ear (7) arranged at one end in the direction of the winding axis P, wherein the wound electrode assembly (5) has a separator extension portion (30) formed by extending the separator (3) longer than the positive electrode (1) and the negative electrode (2) at the other end in the direction of the winding axis P, and in a cross-sectional observation through the winding axis, the separator (3) has a curved shape (region K) convex to the outer peripheral side (n1) of the winding at least in a portion of the separator extension portion (30).

Description

Technical Field

[0001] The present invention relates to a secondary battery and a method for manufacturing the same. Background Art

[0002] Conventionally, secondary batteries are used as power sources for various electronic devices. A secondary battery generally has a structure in which an electrode assembly (electrode body) and an electrolyte are accommodated in an outer casing (casing), and further has external terminals for achieving electrical connection of the secondary battery.

[0003] As an electrode assembly, for example Fig.17 As shown in FIG. 1 , there is known a wound electrode assembly 505 in which a positive electrode 501, a negative electrode 502, and a separator 503 disposed between the positive electrode and the negative electrode are wound. In the wound electrode assembly 505, a collector ear 507 is disposed at one end in the direction of the winding axis P'. Fig.17 As shown, in a structure where such a wound electrode assembly 505 is housed in an outer casing 520 as it is, if an impact is applied to the battery, stress is concentrated between the end T of the wound electrode assembly 505 and the outer casing 520, and sometimes a short circuit occurs between the positive electrode and the negative electrode.

[0004] Therefore, the following technology is disclosed: in the winding axis P' direction of the wound electrode assembly 505, at the end T on the other end opposite to the end having the collector ear 507, the separator is extended longer than the positive electrode and the negative electrode to form a buffer portion for absorbing shock (Patent Document 1). In such a technology, the separator extension portion 5030 is bent in one direction (for example, the thickness direction of the flat columnar shape of the wound electrode assembly) to form a buffer portion for absorbing shock.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2013-164967 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] The inventors of the present invention have found that the buffer portion formed by bending the diaphragm extension portion in one direction (i.e., the thickness direction) cannot fully absorb the impact. In addition, the inventors have found that the buffer portion is a component formed by bending the diaphragm extension portion in only one direction (i.e., the thickness direction), and therefore, there is a risk of the electrode being exposed in the secondary battery and the diaphragm being trapped between the components constituting the outer body when the outer body is sealed.

[0010] An object of the present invention is to provide a secondary battery capable of more adequately absorbing impacts and a method for manufacturing the same.

[0011] An object of the present invention is to provide a secondary battery and a method for manufacturing the same which can more adequately absorb shock and more adequately reduce the risk of electrodes being exposed in the secondary battery and the risk of a separator being trapped between components of an exterior body.

[0012] Technical solutions to technical problems

[0013] The present invention relates to a secondary battery, comprising a wound electrode assembly having a positive electrode, a negative electrode and a separator arranged between the positive electrode and the negative electrode, and a collector ear arranged at one end in the direction of the winding axis P. In the secondary battery, the wound electrode assembly has a separator extension portion at the other end in the direction of the winding axis P, in which the separator is extended longer than the positive electrode and the negative electrode. In a cross-sectional observation through the winding axis, the separator has a curved shape convex toward the outer peripheral side of the winding at least in a portion of the separator extension portion.

[0014] The present invention also relates to a method for manufacturing a secondary battery, comprising a molding step, in which, in a wound electrode assembly obtained by winding a positive electrode, a negative electrode, and a separator arranged between the positive electrode and the negative electrode, a heating block is brought into contact with an extended portion of the separator that is longer than the positive electrode and the negative electrode in the axial direction of the winding.

[0015] Effects of the Invention

[0016] The secondary battery of the present invention absorbs shock more adequately.

[0017] The secondary battery of the present invention can more sufficiently reduce the risk of the electrode being exposed in the secondary battery and the risk of the separator being trapped between components of the outer casing. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic perspective view showing the appearance of an example of the secondary battery of the present invention.

[0019] Figure 2 is a schematic conceptual diagram of a secondary battery according to a first embodiment of the present invention, which is constituted by Figure 1 A schematic cross-sectional view showing a winding axis of a wound electrode assembly of a secondary battery and when a cross section along line AA is viewed in the direction of the arrow.

[0020] Figure 3 This is a schematic perspective view for explaining components constituting a wound electrode assembly of a secondary battery according to the first embodiment of the present invention.

[0021] Figure 4 This is a schematic perspective view for explaining a method of winding a wound electrode assembly constituting the secondary battery according to the first embodiment of the present invention.

[0022] Figure 5 This is a schematic cross-sectional view for explaining a precursor of a wound electrode assembly constituting the secondary battery according to the first embodiment of the present invention.

[0023] Figure 6 This is a schematic cross-sectional view for explaining a method for manufacturing a wound electrode assembly constituting the secondary battery according to the first embodiment of the present invention.

[0024] Figure 7 It is a schematic cross-sectional view for explaining a wound electrode assembly constituting the secondary battery according to the first embodiment of the present invention.

[0025] Figure 8 This is a schematic cross-sectional view for explaining a wound electrode assembly with an insulating tape constituting the secondary battery according to the first embodiment of the present invention.

[0026] Fig. 9 is a schematic conceptual diagram of a secondary battery according to a second embodiment of the present invention, which is constituted by Figure 1 A schematic cross-sectional view showing a winding axis of a wound electrode assembly of a secondary battery and observing a cross section along line AA in the direction of arrows.

[0027] Fig.10 This is a schematic perspective view for explaining components constituting a wound electrode assembly of a secondary battery according to a second embodiment of the present invention.

[0028] Fig.11 This is a schematic perspective view for explaining a method of winding a wound electrode assembly constituting a secondary battery according to a second embodiment of the present invention.

[0029] Fig.12 This is a schematic cross-sectional view for explaining a precursor of a wound electrode assembly constituting a secondary battery according to a second embodiment of the present invention.

[0030] Fig.13 It is a schematic cross-sectional view for explaining a method for manufacturing a wound electrode assembly constituting a secondary battery according to a second embodiment of the present invention.

[0031] Fig.14 It is a schematic cross-sectional view for explaining a wound electrode assembly constituting a secondary battery according to a second embodiment of the present invention.

[0032] Fig.15 This is a schematic cross-sectional view for explaining a wound electrode assembly with an insulating tape constituting a secondary battery according to a second embodiment of the present invention.

[0033] Fig.16 This is a microscope photograph of the vicinity of the bottom extension portion of the secondary battery according to the first embodiment of the present invention.

[0034] Fig.17 It is a schematic conceptual diagram of a secondary battery according to the related art, and is a schematic cross-sectional view passing through a winding axis of a wound electrode assembly constituting the secondary battery. DETAILED DESCRIPTION

[0035] [Secondary battery and method for manufacturing the same]

[0036] The present invention provides a secondary battery. In this specification, the term "secondary battery" refers to a battery that can be repeatedly charged and discharged. "Secondary battery" is not limited to its name, and may also include electrochemical devices such as "power storage devices".

[0037] Hereinafter, the secondary battery and the manufacturing method thereof of the present invention are described in detail using the drawings showing several embodiments. The "cross-sectional observation" mentioned in this specification refers to the cross-sectional state (cross-sectional view) when observed from a direction approximately perpendicular to the winding axis of the wound electrode assembly constituting the secondary battery. In particular, in the case where the wound electrode assembly has a flat columnar shape as described later, "cross-sectional observation" refers to the cross-sectional state (cross-sectional view) when observed from a direction approximately perpendicular to the winding axis of the wound electrode assembly in a manner that minimizes the cross-sectional area. In this specification, the various elements of the drawings are only schematically and exemplarily shown for the purpose of understanding the present invention, and the appearance and size ratio may be different from the actual object. The "up and down direction", "left and right direction" and "front and back direction" used directly or indirectly in this specification are equivalent to the directions corresponding to the up and down direction, left and right direction and front and back direction in the figure, respectively, unless otherwise specified. The same symbol or mark, unless otherwise specified, represents the same component or the same meaning except for the different shapes.

[0038] <First embodiment>

[0039] The secondary battery 100A of this embodiment includes a positive electrode 1, a negative electrode 2, and a separator 3 disposed between the positive electrode and the negative electrode, and generally includes an electrolyte. The secondary battery of the present invention is generally composed of an electrode assembly 5 composed of the positive electrode 1, the negative electrode 2, and the separator 3, and an electrolyte (not shown) sealed in an outer body 6.

[0040] like Figure 1 to Figure 4As shown, the electrode assembly 5 has a winding structure in which the positive electrode 1, the negative electrode 2 and the separator 3 are wound in a roll shape. In detail, the electrode assembly 5 has a winding structure in which an electrode unit (electrode constituent layer) including the positive electrode 1, the negative electrode 2 and the separator 3 disposed between the positive electrode and the negative electrode is wound in a roll shape. When the electrode assembly 5 has such a winding structure, the secondary battery including the electrode assembly is referred to as a "wound-type secondary battery". The winding structure may also be referred to as a jelly roll structure. Figure 1 It is a schematic perspective view showing the appearance of an example of the secondary battery of the present invention. Figure 2 is a schematic conceptual diagram of a secondary battery according to a first embodiment of the present invention, which is constituted by Figure 1 A schematic cross-sectional view showing a winding axis of a wound electrode assembly of a secondary battery and observing a cross section along line AA in the direction of arrows. Figure 3 This is a schematic perspective view for explaining components constituting a wound electrode assembly of a secondary battery according to the first embodiment of the present invention. Figure 4 This is a schematic perspective view for explaining a method of winding a wound electrode assembly constituting the secondary battery according to the first embodiment of the present invention.

[0041] exist Figure 1 as well as Figure 2 In the embodiment, the electrode assembly 5 has a substantially flat columnar shape, but may also have a substantially cylindrical shape. The substantially flat columnar shape is, for example, a shape that can be obtained by pressing a substantially cylindrical shape in its diameter direction, including a substantially elliptical columnar shape.

[0042] In the electrode assembly 5, a collector ear 7 is arranged at one end in the direction of the winding axis P. The collector ear 7 includes a collector ear 71 for the positive electrode and a collector ear 72 for the negative electrode. The collector ear 71 for the positive electrode is electrically connected to the external terminal structure 8 and is led out to the outside through the external terminal structure 8. The external terminal structure 8 is not particularly limited, for example, it can also be embedded and inserted into the through hole of the outer body 6. In detail, the external terminal structure 8 includes: a conductive rivet portion 80, which is mainly used to lead the electrode to the outside; an external gasket portion 81, which is used to ensure the electrical insulation of the conductive rivet portion 80 and the outer body 6 and prevent the leakage of the electrolyte; an internal pole ear 82, which is used to ensure the electrical connection between the conductive rivet portion 80 and the collector ear 7; and an internal gasket portion 83, which is used to ensure the electrical insulation of the internal pole ear 82 and the outer body 6 and prevent the leakage of the electrolyte. The negative electrode collector tab 72 is electrically connected to the outer casing 6 and is led out to the outside through the outer casing 6. The winding axis P may be an axis that bisects the thickness p1 and the depth p2 of the secondary battery 100A and is parallel to the height p3 direction.

[0043] Figure 2In the embodiment, the positive electrode collector tab 71 is electrically connected to the external terminal structure 8, and the negative electrode collector tab 72 is electrically connected to the external terminal structure 8. In this case, the positive electrode collector tab 71 may be in contact with the inner side of the outer casing 6 and electrically connected.

[0044] Moreover, in Figure 2 In the embodiment, the negative electrode collector tab 72 is electrically connected to the inner side of the outer body 6, but one of the positive electrode collector tab 71 and the negative electrode collector tab 72 may be electrically connected to the inner side of the outer body. In this case, the outer body 6 has the same polarity as the collector tab in contact with the inner side thereof. In the case where the outer body 6 is non-conductive, it may be led to the outside via a new external terminal structure.

[0045] From the viewpoint of voltage balance, it is preferred that the positive electrode collector tab 71 is electrically connected to the external terminal structure 8 , and the negative electrode collector tab 72 is electrically connected to the inside of the exterior body 6 .

[0046] like Figure 2 As shown, the electrode assembly 5 has a separator extension portion 30 at the other end opposite to the end having the collector ear 7 in the winding axis P direction. Figure 2 As shown, the electrode assembly 5 usually has a diaphragm extension portion 32 at one end having the collector ear 7 in the direction of the winding axis P. The diaphragm extension portions 30 and 32 respectively refer to portions of the diaphragm 3 extending longer than the positive electrode 1 and the negative electrode 2 in the direction of the winding axis P. Hereinafter, the diaphragm extension portions 30 and 32 are sometimes simply referred to as "bottom extension portion 30" and "top extension portion 32", respectively. It should be noted that the bottom and the top are respectively the bottom and the top when it is assumed that the winding axis P of the wound electrode assembly 5 inside the secondary battery 100A is configured to be parallel to the vertical direction, and the terminal structure 8 described later is located at a higher position. Alternatively, the secondary battery 100A may be configured such that the winding axis P of the wound electrode assembly 5 inside the secondary battery 100A is parallel to the horizontal direction.

[0047] In the present embodiment, when the diaphragm 3 is observed in a cross-section through the winding axis P, at least a portion of the bottom extension portion 30 has a curved shape that bulges toward the outer peripheral side n1 of the winding, and as the bottom extension portion 30, a molded body having flexibility is formed. "The curved shape that bulges toward the outer peripheral side n1" refers to a curved shape that protrudes from the inner peripheral side n2 toward the outer peripheral side n1. The curved shape is a shape in which the diaphragm 3 bends toward the inner peripheral side (i.e., the outer peripheral direction n2) of the winding after the bottom extension portion 30 temporarily bends toward the outer peripheral side (i.e., the outer peripheral direction n1) of the winding toward its front end. Figure 2 In the figure, the region having a curved shape in the bottom extension portion 30 is indicated by "K". Such a region can also be called a "regular region" because the diaphragms 3 are arranged in a substantially regular curved shape. Curvature includes bending and bending. Figure 2As shown in the region K of the bottom extension 30, bending refers to bending in a bay (or bow) shape (i.e., bending in a nearly curved line) and forming a bend with rounded corners, and also includes flexure. Bend refers to bending at an acute angle (i.e., bending in a substantially straight line). From the viewpoint of further improving the impact absorption of the bottom extension 30, "bending" is preferably "bending".

[0048] The diaphragm 3 has a curved shape as described above at the bottom extension 30, and constitutes a molded body with flexibility. Therefore, the bottom extension 30 becomes an impact absorber, which can more fully absorb the impact transmitted from the outside to the secondary battery (for example, the impact from the outer body 6 of the bottom extension 30 in the direction of the winding axis P). In addition, the risk of the electrode being exposed in the secondary battery can be fully reduced, and when the outer body is sealed, the risk of the diaphragm being trapped between the components of the outer body can be further reduced. In addition, such a bottom extension 30 also contributes to the retention of the electrolyte more fully. Fig.16 A microscope photograph of the vicinity of the bottom extension portion 30 of the secondary battery of this embodiment is shown. Fig.16 It can be seen that the diaphragm 3 has a curved shape convex toward the outer peripheral side of the winding at a part of the bottom extension portion 30, and the bottom extension portion 30 constitutes a molded body with flexibility. Figure 2 In the figure, gaps are shown between various elements such as between the positive electrode 1 and the separator 3 and between the negative electrode 2 and the separator 3, but this is only shown for understanding of the present invention and may hardly exist in the actual object. Figures 5 to 9 as well as Figure 12 to Figure 15 The gaps between the various elements are also related to Figure 2 The gap is the same.

[0049] The separator 3 includes a main body 31 adjacent to the bottom extension 30 in the winding axis P direction and arranged between the positive electrode 1 and the negative electrode 2. From the viewpoint of further improving the impact absorption of the bottom extension 30 and more fully reducing the risk of exposure of the electrode in the secondary battery and the risk of the separator being trapped between the components of the outer body, the separator 3 is preferably bent toward the outer peripheral side n1 of the winding at the boundary between the bottom extension 30 and the main body 31. In other words, it is preferred that the bending toward the outer peripheral side n1 of the winding in the curved shape of the separator 3 has already started at the boundary between the bottom extension 30 and the main body 31 of the separator 3.

[0050] For example, Figure 2 In the cross-sectional view through the winding axis P as shown, the electrode assembly 5 is composed of a plurality of separators 3. Figure 2As shown, from the viewpoint of further improving the impact absorption of the bottom extension 30 and more fully reducing the risk of exposure of the electrode in the secondary battery and the risk of the separator being trapped between the components of the outer body, it is preferred that the plurality of separators 3 are arranged so as to overlap with each other in the winding axis P direction of the electrode assembly 5 between adjacent separators in the curved region K of the bottom extension 30. Overlapping with each other in the winding axis P direction means Figure 2 In the bent-shaped area K of the bottom extension portion 30 as shown, for two adjacent diaphragms, the diaphragm arranged on the outer peripheral side overlaps in a manner of enclosing the diaphragm arranged on the inner peripheral side. In detail, for the two adjacent diaphragms, assuming that the diaphragm arranged on the inner peripheral side (especially its bent-shaped portion) is intended to be moved parallel to the direction of the winding axis P (for example, upward), the movement is hindered by the bent-shaped portion of the diaphragm arranged on the outer peripheral side. Such mutual overlap between two adjacent diaphragms preferably occurs between all two adjacent diaphragms, but is not limited to this, and can occur on both sides of the winding axis P, at least between two adjacent diaphragms in the central portion. The two adjacent diaphragms in the central portion are, for example, as shown in FIG. Figure 2 As shown, there are an odd number of ( Figure 2 In the case of 5 electrodes, the separator 3a is disposed between the electrode (one of the positive electrode and the negative electrode) A disposed in the center and the electrode (the other of the positive electrode and the negative electrode) B adjacent to the electrode and disposed on the outer peripheral side n1 on both sides, and the separator 3b is adjacent to the separator 3a and disposed on the inner peripheral side n2. Moreover, for example, in the case where an even number of electrodes are included on both sides of the winding axis P, the two adjacent separators in the central portion refer to the separator between the two electrodes in the center on both sides and the separator adjacent to the separator and disposed on the inner peripheral side n2. Alternatively, in the region K having a curved shape of the bottom extension portion 30, the separator (e.g., 3a) disposed on the outer peripheral side and the separator (e.g., 3b) disposed on the inner peripheral side are partially in contact with each other, and a space (i.e., a space filled with an electrolyte) is sandwiched between them. Alternatively, between the two adjacent diaphragms, the diaphragm arranged on the outer side (e.g., 3a) may overlap in a manner such that a larger portion (e.g., the entire surface) of the diaphragm arranged on the inner side contacts the diaphragm (e.g., 3b) arranged on the inner side and encloses the diaphragm arranged on the inner side.

[0051] exist Figure 2 In the cross-sectional observation through the winding axis P as shown, not all of the plurality of separators 3 need to have a bent shape in the bottom extension 30. At least a portion of the separators may have a bent shape in the bottom extension 30. From the viewpoint of further improving the impact absorption of the bottom extension 30 and more fully reducing the risk of exposure of the electrode in the secondary battery and the risk of the separator being trapped between the components of the outer casing, for example, Figure 2As shown, the electrode assembly 5 preferably includes an odd number of ( Figure 2 In the case of 5 electrodes (in the case of 5 electrodes), the separator 3a between the central electrode (one of the positive electrode and the negative electrode) A on both sides and the electrode (the other of the positive electrode and the negative electrode) B adjacent to the electrode and arranged on the outer peripheral side n1 has a bent shape at the bottom extension part 30. Moreover, for example, in the case where an even number of electrodes are included on both sides of the winding axis P, it is preferred that the separator 3 between the two central electrodes on both sides has a bent shape at the bottom extension part 30. From the viewpoint of further improving the impact absorption of the bottom extension part 30 and more fully reducing the risk of exposure of the electrode in the secondary battery and the risk of the separator being trapped between the components of the outer body, in a preferred embodiment, preferably 30% or more, more preferably 50% or more, and even more preferably 80% or more of all the separators when observed in a cross-section through the winding axis P have a bent shape at the bottom extension part 30.

[0052] The bottom extension portion 30 may include a regular region K where the diaphragms 3 are arranged substantially regularly in a curved shape and an irregular region L where the diaphragms 3 are not arranged regularly in a cross-sectional view passing through the winding axis P. The irregular region L is arranged on the bottom extension portion 30 closer to the front end side of the diaphragm 3 than the regular region K.

[0053] From the viewpoint of further improving the impact absorption of the bottom extension portion 30, Figure 2 As shown, preferably, in the cross-sectional observation through the winding axis P (particularly in the region K having a curved shape), the bottom extension portion 30 of the diaphragm 3 is temporarily bent toward the outer peripheral side n1 of the winding, and then bent toward the inner peripheral side n2, and then extended toward the inner peripheral side n2 relative to the boundary point R between the extension portion 30 and the main body portion 31 of the diaphragm 3. Such an extended form of the diaphragm 3 is preferably present in all diaphragms, but is not limited thereto, and may be present in at least the central portion on both sides of the winding axis P. The central portion diaphragm refers, for example, to Figure 2 As shown, there are an odd number of ( Figure 2 In the case of 5 electrodes, the separator 3a is provided between the central electrode (one of the positive electrode and the negative electrode) A and the electrode (the other of the positive electrode and the negative electrode) B adjacent to the electrode and arranged on the outer side n1. Figure 2 In FIG. 1 , region Q shows the extension of the separator 3 a on the right side relative to the winding axis P. For example, when an even number of electrodes are included on both sides of the winding axis P, the separator in the center refers to the separator between the two electrodes in the center on both sides.

[0054] From the viewpoint of further improving the impact absorption of the bottom extension portion 30, Figure 2As shown, it is preferred that the diaphragm 3, in a cross-sectional view through the winding axis P, extends toward the inner circumference relative to the boundary point R as described above, and then further extends beyond the winding axis P. Such a further extended form of the diaphragm 3 is preferably present in all diaphragms, but is not limited thereto, and may be present on both sides of the winding axis P, or at least in the central portion. For example, Figure 2 As shown, the central diaphragm refers to the diaphragm including an odd number of ( Figure 2 In the case of 5) electrodes, the above-mentioned diaphragm 3a is respectively provided on both sides. Figure 2 In FIG. 1 , region S shows the further extended form of the separator 3a on the right side relative to the winding axis P. For example, when an even number of electrodes are included on both sides of the winding axis P, the separator in the central portion refers to the separator between the two central electrodes on both sides as described above.

[0055] From the viewpoint of further improving the impact absorption of the bottom extension portion 30, Figure 2 As shown, preferably, in the cross-sectional observation through the winding axis P, the diaphragm 3 is temporarily bent toward the outer peripheral side n1 of the winding at the bottom extension portion 30 (especially the region K having a bent shape), and then bent toward the inner peripheral side n2, and then further bent toward the outer peripheral side n1 (i.e., bent). Such a further bending state of the diaphragm toward the outer peripheral side n1 is preferably present in all diaphragms, but is not limited thereto, and can be present in at least the diaphragm in the central portion on both sides of the winding axis P. For example, Figure 2 As shown, the central diaphragm refers to the diaphragm including an odd number of ( Figure 2 In the case of 5) electrodes, the above-mentioned diaphragm 3a is respectively provided on both sides. Figure 2 In FIG. 1 , region S shows the bending state of the diaphragm 3a on the right side relative to the winding axis P, which is further bent toward the outer peripheral side n1. For example, when an even number of electrodes are included on both sides of the winding axis P, the diaphragm in the central portion refers to the diaphragm between the two central electrodes as described above, respectively, on both sides.

[0056] At this time, if Figure 2 As shown, from the viewpoint of further improving the impact absorption of the bottom extension portion 30, the portion further bent toward the outer peripheral side n1 is preferably arranged on the opposite side of the diaphragm with respect to the winding axis P as a reference and the side where the boundary point R exists. That is, in the cross-sectional observation through the winding axis P, the portion of the diaphragm 3 that is further bent toward the outer peripheral side n1 (the portion further bent toward the outer peripheral side n1) is preferably arranged on the opposite side of the diaphragm with respect to the winding axis P as a reference and the side where the boundary point R exists. Such a configuration form of the portion of the diaphragm that is further bent toward the outer peripheral side n1 is preferably present in all diaphragms, but is not limited thereto, and may be present on both sides of the winding axis P, at least in the central portion. For example, Figure 2As shown, the central diaphragm includes an odd number of ( Figure 2 In the case of 5) electrodes, the above-mentioned diaphragm 3a is respectively provided on both sides. Figure 2 In FIG. 1 , region S shows the configuration of the bent portion further toward the outer peripheral side n1 of the diaphragm 3a on the right side with respect to the winding axis P. Furthermore, for example, when an even number of electrodes are included on both sides of the winding axis P, the diaphragm in the central portion refers to the diaphragm between the two central electrodes as described above on both sides.

[0057] The length m1 of the bottom extension portion 30 in the direction of the winding axis P is not particularly limited, but from the viewpoint of balancing the further improvement of the impact absorbency of the bottom extension portion 30 and the improvement of the energy density, the length m1 of the winding axial length M relative to the main body portion 31 is preferably greater than 2% and less than 15%, more preferably greater than 2% and less than 10%, further preferably greater than 2% and less than 8%, particularly preferably greater than 3% and less than 7%, and most preferably greater than 4% and less than 6%.

[0058] The length dimension m1 of the bottom extension portion 30 in the direction of the winding axis P is usually 0.5 mm to 5 mm, more preferably 0.5 mm to 3 mm, and even more preferably 1 mm to 3 mm.

[0059] The winding axial length M of the main body 31 of the separator 3 of the electrode assembly 5 is not particularly limited, and may be, for example, 5 mm to 200 mm, more preferably 10 mm to 30 mm, and even more preferably 15 mm to 25 mm.

[0060] From the viewpoint of more reliably preventing a short circuit between the positive and negative electrodes due to impact and more sufficiently reducing the risk of electrode exposure in the secondary battery and the risk of the separator being trapped between components of the outer casing, the electrode assembly 5 preferably has an insulating tape 4 attached to the bottom extension portion 30 .

[0061] The length dimension m2 of the top extension portion 32 in the direction of the winding axis P is not particularly limited, but is preferably 0.1 mm to 10 mm, more preferably 0.5 mm to 5 mm, and even more preferably 1 mm to 3 mm, from the viewpoint of improving energy density.

[0062] When the electrode assembly 5 has a flat columnar shape, the length dimension of the electrode assembly 5 in the width direction (for example Figure 2 The depth dimension of the electrode assembly 5 in the width direction is not particularly limited, and may be, for example, 5 mm or more and 100 mm or less, more preferably 8 mm or more and 30 mm or less, and further preferably 10 mm or more and 20 mm or less. Figure 2 The length dimension in the left-right direction is not particularly limited, and may be, for example, greater than 1 mm and less than 30 mm, more preferably greater than 1 mm and less than 10 mm, and further preferably greater than 1 mm and less than 5 mm.

[0063] When the electrode assembly 5 has a cylindrical shape, the diameter of the electrode assembly 5 is not particularly limited, and may be, for example, 5 mm to 40 mm, more preferably 8 mm to 30 mm, and even more preferably 10 mm to 20 mm.

[0064] The number of windings of the positive electrode 1, the negative electrode 2, and the separator 3 of the electrode assembly 5 can also be appropriately determined according to the target output and size of the secondary battery. The number of windings can usually be more than two and less than 100, for example, more than three and less than 10.

[0065] The secondary battery of this embodiment can be manufactured by a manufacturing method including the following steps:

[0066] A step of winding a positive electrode 1, a negative electrode 2, and a separator 3 disposed between the positive electrode and the negative electrode to obtain a precursor of a wound electrode assembly (winding step);

[0067] In a precursor of a wound electrode assembly, a heating block is brought into contact with a separator extension portion extending from a positive electrode and a negative electrode in an axial direction of winding to obtain a wound electrode assembly 5 (molding step); and

[0068] The wound electrode assembly 5 is housed in the outer casing 6 , the collector tabs are welded, and an electrolyte is injected into the outer casing 6 (assembly step).

[0069] Winding process

[0070] In this process, if Figure 3 as well as Figure 4 As shown, the positive electrode 1, the negative electrode 2 and two rectangular separators 3 are arranged and wound in a prescribed order to obtain Figure 5 The precursor 50 of the electrode assembly as shown. During winding, a predetermined tension is applied to the separator 3, so that the separator 3 approaches (or gathers) toward its front end in the separator extension portion 300 to the winding axis P. The tension applied to the separator 3 during winding is usually 0.1N or more and 10N or less, and is preferably 0.5N or more and 3N or less from the viewpoint of gathering. In the separator extension portion 300 of the electrode assembly precursor 50, the length dimension x of the separator 3 in the direction of the winding axis P is maintained at approximately the same length in the winding direction toward the winding axis P. Figure 5This is a schematic cross-sectional view for explaining a precursor of a wound electrode assembly constituting a secondary battery according to the first embodiment of the present invention. The "precursor of a wound electrode assembly" refers to an intermediate or intermediate structure for obtaining a wound electrode assembly by molding a bottom extension portion in a molding step described later.

[0071] The size of the separator 3 used is not particularly limited as long as the desired electrode assembly 5 can be obtained. For example, the length dimension w1 in the width direction r of the separator 3 (see Figure 3 ) is usually 105% or more and 300% or less, and particularly 110% or more and 300% or less, relative to the winding axial length M of the main body 31 of the separator 3 of the target electrode assembly 5. Furthermore, for example, the length dimension w2 in the long side direction s of the separator 3 (see Figure 3 ) can be appropriately determined according to the size of the target secondary battery (especially the number of windings of the electrode assembly 5).

[0072] In this process, the precursor of the wound electrode assembly may be pressed in the diameter direction of the wound body as required, thereby forming it in a roughly flat columnar shape. It should be noted that such pressing may also be performed between the molding process and the assembly process described later instead of in this process. From the viewpoint of further improving the impact absorbency of the bottom extension portion 30 and more fully reducing the risk of exposure of the electrode in the secondary battery and the risk of the diaphragm being trapped between the components of the outer body, it is preferred that the pressing be performed between the winding process and the molding process.

[0073] Molding process

[0074] like Figure 6 As shown, in this step, in the precursor 50, the heating block 55 is brought into contact with the separator extension portion 300 extending from the positive electrode and the negative electrode of the separator 3 in the axial direction of the winding, so that the separator extension portion 30 is formed to obtain Figure 7A wound electrode assembly 5 as shown. At this time, the heating block 55 is brought into contact with the diaphragm extension portion 300 until the diaphragm extension portion 300 is bent. As a result, the diaphragm 3 is appropriately deformed and melted in the diaphragm extension portion 300, so that soft molding (i.e., soft shaping) of the diaphragm extension portion 300 can be achieved. Soft molding refers to shaping a molded body with flexibility. As a result, an electrode assembly 5 in which the diaphragm 3 has a bottom extension portion 30 with a curved shape as described above can be obtained. The obtained bottom extension portion 30 includes a molded body with flexibility. For example, even if a precursor is used in which the diaphragm 3 in the diaphragm extension portion is not close to (or gathered) at its front end to the winding axis P, the diaphragm 3 cannot form a bottom extension portion 30 with a curved shape as described above, and as a result, a molded body with flexibility cannot be obtained as the bottom extension portion 30. Moreover, for example, even if a heater other than the heating block (such as a fan heater, a heating wire, etc.) is used, the diaphragm 3 cannot form the bottom extension portion 30 having the above-mentioned curved shape, and as a result, a molded body having flexibility cannot be obtained as the bottom extension portion 30. Figure 6 It is a schematic cross-sectional view for explaining a method for manufacturing a wound electrode assembly (particularly a molding step) constituting the secondary battery according to the first embodiment of the present invention. Figure 7 It is a schematic cross-sectional view for explaining a wound electrode assembly constituting the secondary battery according to the first embodiment of the present invention.

[0075] When the melting point of the polymer material constituting the separator 3 is set to Mp (°C), the surface temperature of the heating block 55 is usually Mp-30 (°C) or more and Mp+30°C or less. From the viewpoint of further improving the impact absorption of the bottom extension 30 and more fully reducing the risk of exposure of the electrode in the secondary battery and the risk of the separator being trapped between the components of the outer body, it is preferably Mp-30 (°C) or more and Mp+20°C or less, and more preferably Mp-30°C or more and Mp+15°C or less. If the surface temperature of the heating block is too high, when the heating block 55 approaches the separator extension 300, the separator 3 begins to melt before the separator 3 is bent, so the separator 3 cannot form the bottom extension 30 having the above-mentioned bending shape, and as a result, a molded body with flexibility cannot be obtained. If the surface temperature of the heating block is too low, the separators 3 are not welded, so the separator 3 cannot form the bottom extension 30 having the above-mentioned bending shape, and as a result, a molded body with flexibility cannot be obtained.

[0076] like Figure 8As shown, the separator extension portion 30 of the electrode assembly 5 is usually attached with an insulating tape 4. In this case, the bottom extension portion 30 is formed as a flexible molded body, so it is very easy to attach the insulating tape 4. In addition, not only can the short circuit between the positive electrode and the negative electrode caused by impact be more reliably prevented, but also the risk of the electrode being exposed in the secondary battery and the risk of the separator being trapped between the components of the outer body can be more fully reduced. Figure 8 This is a schematic cross-sectional view for explaining a wound electrode assembly with an insulating tape constituting the secondary battery according to the first embodiment of the present invention.

[0077] Assembly process

[0078] The electrode assembly 5 obtained in the previous step is housed in the outer casing 6, and the collector ear 7 is welded, and the electrolyte is injected into the outer casing 6. When the outer casing 6 is composed of two parts (for example, a cover part 61 and a main body part 62) as described later, for example, after the electrode assembly 5 is housed and the collector ear 7 is welded and the two parts are welded, the electrolyte is injected from the injection port (not shown) and the injection port is closed by a sealing plug (not shown). The welding of the collector ear 7, the welding of the two parts as the outer casing 6, and the closing by the sealing plug can also be achieved by all methods known in the field of secondary batteries, for example, a laser welding method can also be used. For example Figure 2 As shown, from the viewpoint of ensuring insulation between the electrode assembly 5 and the terminal structure 8 , when the secondary battery includes the separator 9 , the separator 9 may be housed when the outer casing 6 of the electrode assembly 5 is housed.

[0079] ·Materials for secondary batteries

[0080] The positive electrode 1 is composed of at least a positive electrode material layer 12 and a positive electrode collector (foil) 11, and a positive electrode material layer is provided on at least one surface of the positive electrode collector 11. For example, the positive electrode 1 may be provided with a positive electrode material layer 12 on both surfaces of the positive electrode collector 11, or may be provided with a positive electrode material layer 12 on one surface of the positive electrode collector 11. From the viewpoint of further increasing the capacity of the secondary battery, the preferred positive electrode 1 is provided with a positive electrode material layer 12 on both surfaces of the positive electrode collector 11. The positive electrode collector 11 does not necessarily have a positive electrode material layer on both surfaces or on the entire surface of one surface. Usually, the positive electrode collector 11 has a portion where a positive electrode material layer is not provided on both surfaces at both ends in the direction of the winding axis P and at both ends in the direction perpendicular to the winding axis P (i.e., the winding direction or the long side direction). The positive electrode collector 11 may also include a portion where a positive electrode material layer 12 is provided on both surfaces and a portion where a positive electrode material layer 12 is provided on only one surface. The positive electrode material layer 12 contains a positive electrode active material.

[0081] The negative electrode 2 is composed of at least a negative electrode material layer 22 and a negative electrode collector (foil) 21, and the negative electrode material layer 22 is provided on at least one surface of the negative electrode collector 21. For example, the negative electrode 2 may be provided with a negative electrode material layer 22 on both surfaces of the negative electrode collector 21, or may be provided with a negative electrode material layer 22 on one surface of the negative electrode collector 21. From the viewpoint of further increasing the capacity of the secondary battery, the preferred negative electrode 2 is provided with a negative electrode material layer 22 on both surfaces of the negative electrode collector 21. The negative electrode collector 21 does not necessarily have a negative electrode material layer on both surfaces or on the entire surface of one surface. Usually, the negative electrode collector 21 has a portion where a negative electrode material layer is not provided on both surfaces at both ends in the winding axis P direction and at both ends in the direction perpendicular to the winding axis P direction (i.e., the winding direction or the long side direction). The negative electrode collector 21 may also include a portion where a negative electrode material layer 22 is provided on both surfaces and a portion where a negative electrode material layer 22 is provided on only one surface. The negative electrode material layer includes a negative electrode active material.

[0082] The positive electrode active material contained in the positive electrode material layer 12 and the negative electrode active material contained in the negative electrode material layer 22 are substances that directly participate in the transmission of electrons in the secondary battery, and are the main substances of the positive and negative electrodes responsible for charging and discharging, that is, the battery reaction. More specifically, because of the "positive electrode active material contained in the positive electrode material layer" and the "negative electrode active material contained in the negative electrode material layer", ions are brought to the electrolyte, and such ions move between the positive electrode and the negative electrode to transfer electrons for charging and discharging. The positive electrode 1 and the negative electrode 2 are preferably electrodes that can embed and deintercalate lithium ions, that is, the positive electrode material layer 12 and the negative electrode material layer 22 are preferably layers that can embed and deintercalate lithium ions. In other words, it is preferably a secondary battery in which lithium ions move between the positive electrode and the negative electrode via the electrolyte to charge and discharge the battery. In the case where lithium ions participate in charging and discharging, the secondary battery involved in this embodiment is equivalent to the so-called "lithium ion battery".

[0083] When the positive electrode active material of the positive electrode material layer 12 is composed of, for example, granules, a binder (also referred to as an "adhesive") is preferably included in the positive electrode material layer in order to ensure sufficient contact and shape retention of the particles. Furthermore, a conductive aid is preferably included in the positive electrode material layer in order to facilitate the transfer of electrons that promote the battery reaction. Similarly, when the negative electrode active material of the negative electrode material layer 22 is composed of, for example, granules, a binder is preferably included in order to ensure sufficient contact and shape retention of the particles, and a conductive aid may also be included in the negative electrode material layer in order to facilitate the transfer of electrons that promote the battery reaction. In this way, because they are in a form composed of multiple components, the positive electrode material layer and the negative electrode material layer can also be referred to as a "positive electrode composite material layer" and a "negative electrode composite material layer", etc., respectively.

[0084] The positive electrode active material is preferably a material that helps to embed and de-embed lithium ions. According to this viewpoint, the positive electrode active material is preferably, for example, a lithium-containing composite oxide. More specifically, the positive electrode active material is preferably a lithium transition metal composite oxide containing lithium and at least one transition metal selected from the group consisting of cobalt, nickel, manganese and iron. In other words, in the positive electrode material layer of the secondary battery involved in this embodiment, it is preferred to include such a lithium transition metal composite oxide as the positive electrode active material. For example, the positive electrode active material may also be lithium cobaltate, lithium nickelate, lithium manganate, lithium iron phosphate, or a portion of these transition metals replaced by other metals. Such a positive electrode active material may also be included as a single species, or may be included in combination of two or more species. In a more preferred embodiment, the positive electrode active material contained in the positive electrode material layer becomes lithium cobaltate.

[0085] As the binder that can be included in the positive electrode material layer 12, there is no particular restriction, but at least one selected from the group consisting of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer and polytetrafluoroethylene can be cited. As the conductive aid that can be included in the positive electrode material layer, there is no particular restriction, and at least one selected from carbon black such as thermal black, furnace black, channel black, Ketjen black and acetylene black, graphite, carbon nanotubes or vapor-deposited carbon fibers, metal powders such as copper, nickel, aluminum and silver, and polyphenyl derivatives can be cited. In a more preferred embodiment, the binder of the positive electrode material layer is polyvinylidene fluoride, and in other more preferred embodiments, the conductive aid of the positive electrode material layer is carbon black. In a further preferred embodiment, the binder and the conductive aid of the positive electrode material layer are a combination of polyvinylidene fluoride and carbon black.

[0086] The thickness of the positive electrode material layer 12 is not particularly limited, and may be, for example, 1 μm to 300 μm, and particularly 5 μm to 200 μm. The thickness of the positive electrode material layer is the thickness inside the secondary battery, and the average value of the measured values ​​at any 50 locations is used.

[0087] The negative electrode active material is preferably a material that contributes to the insertion and extraction of lithium ions. From this viewpoint, the negative electrode active material is preferably, for example, various carbon materials, oxides, or lithium alloys.

[0088] As various carbon materials for negative electrode active materials, graphite (natural graphite, artificial graphite), hard carbon, soft carbon, diamond-like carbon, etc. can be cited. In particular, graphite is preferred in that it has high electronic conductivity and excellent adhesion to the negative electrode collector. As oxides for negative electrode active materials, at least one selected from the group consisting of silicon oxide, tin oxide, indium oxide, zinc oxide, and lithium oxide can be cited. The lithium alloy of the negative electrode active material can be any metal that can be formed with a lithium alloy, for example, it can be a divalent, trivalent, or higher alloy of metals such as Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, and lithium. Such oxides are preferably amorphous as their structural form. This is because it is difficult to cause degradation due to inhomogeneities such as crystal grain boundaries or defects. In a more preferred embodiment, the negative electrode active material of the negative electrode material layer becomes artificial graphite.

[0089] As the binder that can be included in the negative electrode material layer 22, there is no particular restriction, and at least one selected from the group consisting of styrene-butadiene rubber, polyacrylic acid, polyvinylidene fluoride, polyimide resin and polyamide-imide resin can be cited. In a more preferred embodiment, the binder contained in the negative electrode material layer becomes styrene-butadiene rubber. As the conductive aid that can be included in the negative electrode material layer, there is no particular restriction, but at least one selected from carbon black such as thermal cracking carbon black, furnace black, channel black, Ketjen black and acetylene black, graphite, carbon nanotubes or vapor-grown carbon fibers, metal powders such as copper, nickel, aluminum and silver, and polyphenyl derivatives can be cited. It should be noted that the negative electrode material layer may also include a component derived from a thickener component (such as carboxymethyl cellulose) used in battery manufacturing.

[0090] In a further preferred embodiment, the negative electrode active material and the binder of the negative electrode material layer are a combination of artificial graphite and styrene-butadiene rubber.

[0091] The thickness of the negative electrode material layer 22 is not particularly limited, and may be, for example, 1 μm to 300 μm, and particularly 5 μm to 200 μm. The thickness of the negative electrode material layer is the thickness inside the secondary battery, and the average value of the measured values ​​at any 50 locations is used.

[0092] The positive electrode collector 11 and the negative electrode collector 21 used for the positive electrode 1 and the negative electrode 2 are components that help collect or supply electrons generated by the active material due to the battery reaction. Such a collector can be a sheet-like metal component, or it can have a porous or perforated form. For example, the collector can also be a metal foil, a punched metal, a mesh or a metal plate mesh. The positive electrode collector 11 for the positive electrode 1 is preferably formed of a metal foil containing at least one selected from the group consisting of aluminum, stainless steel, and nickel, and can also be, for example, aluminum foil. On the other hand, the negative electrode collector 21 for the negative electrode 2 is preferably formed of a metal foil containing at least one selected from the group consisting of copper, stainless steel, and nickel, and can also be, for example, copper foil.

[0093] The diaphragm 3 is a component provided from the viewpoint of preventing short circuits caused by contact between the positive and negative electrodes and maintaining electrolytes. In other words, the diaphragm can be said to be a component that prevents contact between electrons of the positive electrode and the negative electrode and allows ions to pass through. The diaphragm is preferably a porous or microporous insulating component having a membrane morphology due to its small thickness. Although it is only an example after all, a microporous film made of polyolefin can also be used as a diaphragm. In this regard, the microporous film used as a diaphragm can also contain only polyethylene (PE) or only polypropylene (PP) as a polyolefin. Furthermore, the diaphragm can also be a laminate composed of a "microporous film made of PE" and a "microporous film made of PP". The surface of the diaphragm can also be covered with an inorganic particle coating and / or an adhesive layer. The surface of the diaphragm can also be adhesive.

[0094] The thickness of the separator 3 is not particularly limited, and can be, for example, 1 μm or more and 100 μm or less, and particularly 5 μm or more and 20 μm or less. The thickness of the separator is the thickness inside the secondary battery (particularly the thickness between the positive electrode and the negative electrode), and the average value of the measured values ​​at any 50 locations is used.

[0095] The electrolyte facilitates the movement of metal ions released from the electrode (positive electrode / negative electrode). The electrolyte may also be a "non-aqueous" electrolyte such as an organic electrolyte and an organic solvent, or may be an "aqueous" electrolyte containing water. The secondary battery of the present invention is preferably a non-aqueous electrolyte secondary battery using an electrolyte containing a "non-aqueous" solvent and a solute as an electrolyte. The electrolyte may have a liquid or gel-like form (it should be noted that the "liquid" non-aqueous electrolyte in this specification is also referred to as a "non-aqueous electrolyte solution").

[0096] As a specific non-aqueous electrolyte solvent, it is preferably composed of at least carbonate. Such carbonate can also be cyclic carbonate and / or chain carbonate. Although there is no particular restriction, as cyclic carbonate, at least one selected from the group consisting of propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC) and vinylene carbonate (VC) can be cited. As chain carbonate, at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and diphenyl carbonate (DPC) can be cited. In a preferred embodiment of the present invention, a combination of cyclic carbonate and chain carbonate is used as a non-aqueous electrolyte, for example, a mixture of ethylene carbonate and diethyl carbonate is used.

[0097] As a specific solute of the non-aqueous electrolyte, for example, a Li salt such as LiPF 6 and LiBF 4 is preferably used.

[0098] All insulating tapes used in the field of secondary batteries can be used as the insulating tape 4. The insulating tape 4 is an insulating tape having an adhesive layer on one side (i.e., the side of the bottom extension portion 30), and can be composed of polymers such as polyester (e.g., polyethylene terephthalate), polyimide, polyamide, polyamide-imide, and polyolefin (e.g., polyethylene, polypropylene).

[0099] The outer body 6 is usually a hard shell, which is composed of two parts such as a cover 61 and a main body 62. For example, when the outer body 6 is composed of a cover 61 and a main body 62, the cover 61 and the main body 62 are sealed after the electrode assembly 5, the electrolyte and the collector ear 7, and the external terminal structure 8 is stored as needed. As a sealing method, there is no particular limitation, for example, laser irradiation method, etc. can be cited. As a material constituting the cover 61 and the main body 62, all materials that can constitute a hard shell type outer body in the field of secondary batteries can be used. Such a material can also be a conductive material that can realize the movement of electrons, or it can also be an insulating material that cannot realize the movement of electrons. As a conductive material, for example, conductive materials such as aluminum, nickel, iron, copper, and stainless steel can be cited. As an insulating material, for example, insulating polymer materials such as polyester (such as polyethylene terephthalate), polyimide, polyamide, polyamide-imide, and polyolefin (such as polyethylene, polypropylene) can be cited. The cover 61 and the main body 62 are preferably composed of stainless steel. The size of the cover 61 and the main body 62 is mainly determined by the size of the electrode assembly, and preferably has a structure that can prevent the electrode assembly from moving in the outer body when the electrode assembly is stored (for example, the electrode assembly is Figure 2By preventing the movement of the electrode assembly, the electrode assembly can be prevented from being damaged, and the safety of the secondary battery is improved. It should be noted that the outer body 6 can also be a flexible shell such as a bag made of a laminated film.

[0100] The thickness of the outer casing 6 is not particularly limited, and may be, for example, 10 μm to 200 μm, particularly 40 μm to 100 μm. The thickness of the outer casing is an average value of measured values ​​at any 50 locations.

[0101] All collector tabs used in the field of secondary batteries can be used as the collector tab 7. Such a collector tab is made of a material that can realize the movement of electrons, and is usually made of a conductive material such as aluminum, nickel, iron, copper, stainless steel, etc. The shape of the collector tab is not particularly limited, and it can be, for example, linear or plate-shaped. Figure 4 In the figure, the collector ears 71 and 72 are both arranged near the axis of the wound body obtained by winding, but are not limited to this. They can also be arranged near the axis of the wound body independently, near the periphery of the wound body, or between the axis and the periphery of the wound body.

[0102] The conductive riveting portion 80 and the internal tab 82 of the external terminal structure 8 can be made of a material that enables the movement of electrons, and are usually made of conductive materials such as aluminum, nickel, iron, copper, stainless steel, etc. The external gasket portion 81 and the internal gasket portion 83 can be made of a material that does not enable the movement of electrons, and are usually made of insulating polymer materials such as polyester (e.g., polyethylene terephthalate), polyimide, polyamide, polyamide-imide, polyolefin (e.g., polyethylene, polypropylene), etc.

[0103] As the spacer 9, all spacers used in the field of secondary batteries can be used. The spacer 9 is not particularly limited as long as it prevents the contact of electrons between the electrode assembly 5 (especially the electrode) and the outer body (especially the external terminal structure 8). As materials constituting the spacer 9, various insulating polymers such as polyolefins (polyethylene, polypropylene), polyesters (polyethylene terephthalate, polybutylene terephthalate), and acrylic polymers can generally be cited. As long as the spacer 9 can prevent the contact between the electrode assembly 5 (especially the electrode) and the outer body (especially the external terminal structure 8), it can have any form, for example, it can also have the form of a film, a sheet, a plate or a fabric (such as a non-woven fabric).

[0104] <Second embodiment>

[0105] The secondary battery 100B of the present embodiment is the same as the secondary battery 100A of the first embodiment except for the following features.

[0106] like Fig. 9 As shown, in a cross-sectional view passing through the winding axis P, the separator 3 has a curved shape convex toward the outer peripheral side n1 of the winding in the entire bottom extension portion 30 ′, and a molded body having flexibility is configured as the bottom extension portion 30 ′.

[0107] The bottom extension 30' is the same as the bottom extension 30 of the first embodiment except that the diaphragm 3' has a curved shape that is convex toward the outer peripheral side n1 of the winding in the entire bottom extension 30'. The bottom extension 30' generally does not have the irregular area L as the bottom extension 30 has, but it does not mean that it cannot have the irregular area L, and the irregular area L may be present at the front end of the diaphragm 3.

[0108] The electrode assembly 5 ′ is the same as the electrode assembly 5 of the first embodiment except that it has the above-mentioned bottom extension portion 30 ′ instead of the bottom extension portion 30 .

[0109] In the cross-sectional view through the winding axis P (particularly the region K having a curved shape), from the viewpoint of further improving the impact absorption of the bottom extension portion 30', as in the first embodiment, Fig. 9 As shown, preferably, the diaphragm 3 ′ is temporarily bent toward the outer circumference n1 of the winding at the bottom extension portion 30 ′, then bent toward the inner circumference n2 , and then extended toward the inner circumference n2 relative to the boundary point R between the extension portion 30 ′ and the main body portion 31 of the diaphragm 3 .

[0110] The separator 3 ′ is the same as the separator 3 of the first embodiment except for a different shape, as will be described later in the method for manufacturing the secondary battery 100B of the present embodiment.

[0111] In the secondary battery 100B of the present embodiment, the effects obtained in the secondary battery 100A of the first embodiment are obtained, and the following effects are obtained.

[0112] In the secondary battery 100B (particularly the wound electrode assembly 5') of the present embodiment, the separator 3' has a curved shape that is convex toward the outer peripheral side n1 of the winding in the entire bottom extension portion 30' when viewed in cross section along the winding axis P as described above, so that the impact absorption of the bottom extension portion 30' is further improved.

[0113] The method for manufacturing the secondary battery 100B of the present embodiment is the same as the method for manufacturing the secondary battery 100A of the first embodiment except for the following features.

[0114] As the diaphragm, a diaphragm 3' having a different shape from the diaphragm 3 of the first embodiment is used. The shape is a plan view shape, for example, a plan view shape when the diaphragm is placed on a surface with the largest area.

[0115] like Fig.10 As shown, the diaphragm 3' may be a diaphragm whose length dimension in the width direction r gradually decreases in the long side direction s and has a trapezoidal shape. Fig.10 This is a schematic perspective view for explaining components constituting a wound electrode assembly of a secondary battery according to a second embodiment of the present invention.

[0116] The size of the separator 3' used is not particularly limited as long as the desired electrode assembly 5' can be obtained. For example, the length dimension w3 of the long side in the width direction r of the separator 3' (see Fig.10 ) is usually 105% or more and 300% or less, and particularly 110% or more and 300% or less, relative to the winding axial length M of the main body 31 of the separator 3' of the target electrode assembly 5'. The length dimension w4 of the short side in the width direction r of the separator 3' (see Fig.10 ) is usually 100% or more and 300% or less, and particularly 105% or more and 250% or less, relative to the winding axial length M of the main body 31 of the separator 3' of the target electrode assembly 5'. Also, for example, the length dimension w4 of the long side direction s of the separator 3' (see Fig.10 ) may be appropriately determined according to the size of the target secondary battery (particularly the number of windings of the electrode assembly 5').

[0117] In the winding process, Fig.11 As shown, the following method uses the diaphragm 3' to obtain Fig.12 The precursor 50' of the electrode assembly shown is as follows:

[0118] The winding is started from the end portion of the separator 3' where the length dimension in the width direction r is relatively short.

[0119] Fig.11 This is a schematic perspective view for explaining a method of winding a wound electrode assembly constituting a secondary battery according to a second embodiment of the present invention.

[0120] Fig.12 This is a schematic cross-sectional view for explaining a precursor of a wound electrode assembly constituting a secondary battery according to a second embodiment of the present invention.

[0121] During winding, by applying the same predetermined tension as in the first embodiment to the separator 3', a precursor 50' is obtained in which the separator 3' approaches (or gathers) toward its front end in the separator extension portion 300' to the winding axis P. In the separator extension portion 300' of the electrode assembly precursor 50', the length dimension x' of the separator 3' in the direction of the winding axis P gradually decreases toward the winding axis P in the winding direction.

[0122] In the molding process, Fig.13 As shown, in the precursor 50', the heating block 55 is brought into contact with the separator extension portion 300' formed by extending the separator 3' longer than the positive electrode and the negative electrode in the winding axial direction to form the separator extension portion 300', thereby obtaining Fig.14 A wound electrode assembly 5' as shown. At this time, the heating block 55 is brought into contact with the diaphragm extension portion 300' until the diaphragm extension portion 300' is bent. As a result, the diaphragm 3' is appropriately deformed and melted in the diaphragm extension portion 300', so that soft molding (i.e., soft shaping) of the diaphragm extension portion 300' can be achieved. As a result, an electrode assembly 5' can be obtained in which the diaphragm 3' has a bottom extension portion 30' having a curved shape as described above. The obtained bottom extension portion 30' includes a molded body having flexibility. For example, even if a precursor is used in which the diaphragm 3' in the diaphragm extension portion is not close to (or gathered) the winding axis P toward its front end, the diaphragm 3' cannot form a bottom extension portion 30' having a curved shape as described above, and as a result, a molded body having flexibility cannot be obtained as the bottom extension portion 30'. Furthermore, even if a heater other than the heating block (eg, a fan heater, a heating wire, etc.) is used, the diaphragm 3' cannot form the bottom extension 30' having the above-mentioned curved shape, and as a result, a molded body having flexibility cannot be obtained as the bottom extension 30'. Fig.13 It is a schematic cross-sectional view for explaining a method for manufacturing a wound electrode assembly constituting a secondary battery according to a second embodiment of the present invention (particularly a molding step). Fig.14 It is a schematic cross-sectional view for explaining a wound electrode assembly constituting a secondary battery according to a second embodiment of the present invention.

[0123] The surface temperature of the heating block 55 is the same as that of the heating block 55 in the manufacturing method of the first embodiment. If the surface temperature of the heating block is too high, when the heating block 55 approaches the diaphragm extension portion 300', the diaphragm 3' begins to melt before the diaphragm 3 is bent, so that the diaphragm 3' cannot form the bottom extension portion 30' having the above-mentioned bending shape, and as a result, a molded body with flexibility cannot be obtained. If the surface temperature of the heating block is too low, the diaphragms 3' are not welded together, so that the diaphragm 3' cannot form the bottom extension portion 30' having the above-mentioned bending shape, and as a result, a molded body with flexibility cannot be obtained.

[0124] Usually Fig.15As shown, the insulating tape 4 is attached to the separator extension 30' of the electrode assembly 5'. At this time, the bottom extension 30' is formed as a flexible molded body, so it is very easy to attach the insulating tape 4. In addition, not only can the short circuit between the positive electrode and the negative electrode caused by impact be more reliably prevented, but also the risk of the electrode being exposed in the secondary battery and the risk of the separator being trapped between the components of the outer body can be more fully reduced. Fig.15 This is a schematic cross-sectional view for explaining a wound electrode assembly with an insulating tape constituting a secondary battery according to a second embodiment of the present invention.

[0125] Industrial Availability

[0126] The secondary battery involved in the present invention can be used in various fields where electricity storage is assumed. Although it is just an example after all, the secondary battery involved in the present invention, especially the non-aqueous electrolyte secondary battery, can be used in the electrical / information / communication field using mobile devices, etc. (for example, including mobile phones, smart phones, smart watches, notebook computers, digital cameras, activity meters, ARM computers, electronic paper, RFID tags, card-type electronic money and other small electronic devices, etc., or the field of mobile devices); household / small industrial use (for example, power tools, golf carts, household / nursing / industrial robots); large industrial use (for example, forklifts, elevators, port cranes); transportation system field (for example, hybrid vehicles, electric vehicles, buses, trams, electric bicycles, electric motorcycles and other fields); power system use (for example, various power generation, load regulators, smart grids, ordinary household installation type power storage systems and other fields); medical use (medical equipment such as hearing aids and headphones), medical use (dose management system and other fields); and IoT field, space / deep sea use (for example, space probes, diving research vessels and other fields). The present invention can also be applied.

[0127] Explanation of symbols

[0128] 1: Positive electrode

[0129] 2: Negative electrode

[0130] 3: Diaphragm

[0131] 4: Insulation tape

[0132] 5: Electrode assembly

[0133] 6: Exterior body

[0134] 7: Collector ear

[0135] 8: External terminal structure

[0136] 9: Spacer

[0137] 11: Positive electrode collector

[0138] 12: Positive electrode material layer

[0139] 21: Negative electrode collector

[0140] 22: Negative electrode material layer

[0141] 30, 30': bottom extension of the diaphragm

[0142] 31: Main body 31 of the diaphragm

[0143] 32: Top extension of the diaphragm

[0144] 61: Exterior body cover

[0145] 62: Main part of outer body

[0146] 80: Conductive riveting part

[0147] 81: External gasket

[0148] 82: Internal tabs

[0149] 83: Internal gasket

[0150] 100, 100A, 100B: secondary battery.

Claims

1. A secondary battery comprising: A wound electrode assembly and a collector ear, wherein the wound electrode assembly is wound with a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and the collector ear is disposed at one end in the direction of the winding axis P, wherein: The wound electrode assembly has a separator extension portion at the other end in the direction of the winding axis P, in which the separator is extended longer than the positive electrode and the negative electrode. In a cross-sectional view through the axis of the winding, the diaphragm has a curved shape that is convex toward the outer peripheral side of the winding at least in a portion of the diaphragm extension portion, The bent shape is a shape in which the diaphragm is bent toward the inner peripheral side of the winding after the diaphragm extending portion is temporarily bent toward the outer peripheral side of the winding toward the front end of the diaphragm extending portion.

2. The secondary battery according to claim 1, wherein The flexion is a bend in the shape of a bow.

3. The secondary battery according to claim 1, wherein The separator includes: the separator extension portion having the bent shape; and a main body portion disposed between the positive electrode and the negative electrode. In a cross-sectional view passing through the axis P, after the diaphragm extension portion bends toward the inner peripheral side, the diaphragm extends toward the inner peripheral side relative to a boundary point R between the diaphragm extension portion and the main body portion of the diaphragm.

4. The secondary battery according to claim 3, wherein In a cross-sectional view taken along the axis P, the diaphragm extends toward the inner circumference relative to the boundary point and then extends beyond the axis P.

5. The secondary battery according to claim 1, wherein In a cross-sectional view taken along the axis P, the diaphragm is bent toward the inner peripheral side at the diaphragm extension portion and then further bent toward the outer peripheral side.

6. The secondary battery according to claim 5, wherein In the cross-sectional view passing through the axis P, the portion of the diaphragm further bent toward the outer peripheral side is arranged on the side opposite to the side where the boundary point R exists with reference to the axis P.

7. The secondary battery according to claim 1, wherein The separator includes: the separator extension portion having the bent shape; and a main body portion disposed between the positive electrode and the negative electrode. The diaphragm is bent toward the outer peripheral side of the winding at a boundary between the diaphragm extension portion and the main body portion.

8. The secondary battery according to claim 7, wherein The diaphragm extension portion having the bent shape of the diaphragm has an axial length m1 that is 2% or more and 15% or less with respect to the axial length M of the main body portion.

9. The secondary battery according to any one of claims 1 to 8, wherein The wound electrode assembly includes a plurality of separators in a cross-sectional view passing through the winding axis. The plurality of separators are arranged so as to overlap with each other in the direction of the axis P of the wound electrode assembly in the region K having the bent shape of the separator extension portion.

10. The secondary battery according to any one of claims 1 to 8, wherein The wound electrode assembly includes an insulating tape attached to the separator extension portion having the bent shape.

11. The secondary battery according to any one of claims 1 to 8, wherein The diaphragm extension portion of the diaphragm having the bent shape serves as a shock absorber.

12. The secondary battery according to any one of claims 1 to 8, wherein The wound electrode assembly, the collector tab, and the electrolyte are sealed in an outer casing. The outer casing is a hard shell type outer casing.

13. The secondary battery according to claim 12, wherein: The outer casing is a conductive hard shell type outer casing.

14. The secondary battery according to claim 13, wherein The collector tabs include a positive electrode collector tab and a negative electrode collector tab. One of the positive electrode collector tab and the negative electrode collector tab is electrically connected to the inside of the outer casing, The outer casing has the same polarity as that of the collector tab in contact with the inner side.

15. The secondary battery according to claim 14, wherein The outer casing has a negative polarity.

16. The secondary battery according to claim 12, wherein The electrolyte is a non-aqueous electrolyte.

17. The secondary battery according to any one of claims 1 to 8, wherein The positive electrode and the negative electrode are electrodes capable of inserting and extracting lithium ions.

18. A method for manufacturing a secondary battery, manufacturing the secondary battery according to any one of claims 1 to 17, the manufacturing method comprising: In the molding step, in a precursor of a wound electrode assembly obtained by winding a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, a heating block is brought into contact with an extended portion of the separator that is extended longer than the positive electrode and the negative electrode in an axial direction of the winding.

19. The method for manufacturing a secondary battery according to claim 18, wherein: In the molding step using the heating block, the heating block is brought into contact with the diaphragm extension portion until the diaphragm extension portion bends.

20. The method for manufacturing a secondary battery according to claim 18, wherein: When the melting point of the polymer material constituting the separator is defined as Mp° C., the heating block has a surface temperature of Mp-30° C. or higher and Mp+30° C. or lower.

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