Secondary battery

Abstract

A secondary battery in which problems existing in the prior art can be eliminated can be provided. A secondary battery according to the present disclosure is provided with: a laminated electrode body including a plurality of first electrode plates, a plurality of second electrode plates, and a belt-shaped separator; and a battery case. The separator includes: a multi-fold portion bent into a multi-fold shape so as to be disposed between the first electrode plate and the second electrode plate; and a winding portion wound around the outer periphery of a portion where the first electrode plate, the second electrode plate, and the multi-fold portion are laminated. The diaphragm includes a starting end portion which is an end portion on one side in the lengthwise direction and a terminal end portion which is an end portion on the other side in the lengthwise direction. The terminal part is located at the winding ending end of the winding part. The multi-folding portion includes a first folding portion and a second folding portion. The diaphragm is provided with an extending part which is positioned closer to the starting end part side than the multi-folding part and is configured between the second bending part and the winding part. In the lamination direction of the first electrode plate and the second electrode plate, the outer surfaces of the two electrode plates located on the outermost surface side are covered by a diaphragm.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a secondary battery. BACKGROUND

[0002] As one form of an electrode body possessed by a secondary battery, a laminated electrode body in which a plurality of positive electrodes and a plurality of negative electrodes are alternately laminated with a separator interposed therebetween is known. In the laminated electrode body, a form in which the separator is formed into a plurality of folds in a manner of being interposed between the positive electrode and the negative electrode is known (for example, refer to Patent Literature 1). Various patterns of the electrode body in which the separator is formed into the plurality of folds are disclosed in Patent Literature 1.

[0003] PRIOR ART DOCUMENTS

[0004] PATENT LITERATURE

[0005] Patent Literature 1: International Publication No. 2019 / 064740 SUMMARY

[0006] In recent years, extension of a cruising range of a pure electric vehicle (BEV) and the like is sought, and a secondary battery mounted on the pure electric vehicle is also being upsized. The upsizing of the secondary battery brings about an increase in weight of an electrode body. In a case where the weight of the electrode body is increased, from the viewpoint of reliability of the secondary battery, suppression of electrode damage caused by an impact, a vibration, and the like at the time of manufacturing is more sought.

[0007] Thus, the present disclosure provides a secondary battery that eliminates the problems of the related art.

[0008] The secondary battery disclosed herein comprises: a laminated electrode body including a plurality of first electrode plates, a plurality of second electrode plates having polarities different from those of the first electrode plates, and a strip-shaped separator; and a battery case housing the laminated electrode body. The separator comprises: a multi-fold portion bent into a multi-fold shape so as to be disposed between the first electrode plate and the second electrode plate; and a winding portion wound around the outer periphery of the portion of the multi-fold portion where the first electrode plate, the second electrode plate, and the separator are stacked. The separator comprises a starting end portion serving as one end in the longitudinal direction of the separator and a terminal end portion serving as the other end. The terminal end portion is located at the winding end of the winding portion. The multi-fold portion comprises: a first bent portion disposed on one side perpendicular to the direction in which the first and second electrode plates are stacked; and a second bent portion disposed on the other side perpendicular to the direction in which the first and second electrode plates are stacked. The separator has an extension portion located closer to the starting end portion than the multi-fold portion and disposed between the second bent portion and the wrapped portion. In the stacking direction of the plurality of first electrode plates and the plurality of second electrode plates, the outer surface of one of the plurality of first electrode plates and the plurality of second electrode plates is covered by the separator, and the outer surface of the other electrode plate is also covered by the separator.

[0009] According to this structure, a secondary battery that solves the problems of the conventional technology can be provided. In other words, according to this structure, a secondary battery that can suppress electrode damage caused by vibration or impact during manufacturing at a high level can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a perspective view schematically showing a secondary battery according to one embodiment of an example of the secondary battery disclosed herein.

[0011] Figure 2 Yes Figure 1 An upside-down perspective view of a secondary battery.

[0012] Figure 3 It is a schematic representation Figure 1 A cross-sectional view of the internal structure of a secondary battery along the main surface of a battery case of the secondary battery.

[0013] Figure 4 yes Figure 1 1 is a perspective view of a secondary battery, schematically showing a case body in a transparent manner.

[0014] Figure 5 It is a schematic representation Figure 1 A cross-sectional view showing the structure of an electrode body of a secondary battery.

[0015] Figure 6 is a cross-sectional view taken in the direction perpendicular to the long side of the battery case of the secondary battery and perpendicular to the bottom surface of the secondary battery Figure 1

[0016] Figure 7 is an expanded view of an insulating sheet used for the secondary battery Figure 1

[0017] Figure 8 is a view of an insulating sheet used for the secondary battery 100, as viewed from the direction of the bottom surface of the battery case of the secondary battery Figure 1 DETAILED DESCRIPTION

[0018] Hereinafter, embodiments related to the present disclosure will be described with reference to the drawings. Also, matters not mentioned in the present specification and matters required for the implementation of the present disclosure can be understood as design matters of those skilled in the art based on the prior art. The present disclosure can be implemented based on the content disclosed in the present specification and technical common sense in the art. Also, in the following drawings, the same reference numerals are assigned to members, portions that play the same role, and are described. Also, the dimensional relationship (length, width, thickness, etc.) in each drawing does not reflect the actual dimensional relationship. Also, in the present specification, a numerical range expressed as "A to B" includes A and B.

[0019] Also, in the present specification, "secondary battery" means a power storage device that can be repeatedly charged and discharged. Also, in the present specification, "lithium-ion secondary battery" means a secondary battery that uses lithium ions as charge carriers and realizes charge and discharge by charge movement of lithium ions between positive and negative electrodes.

[0020] Figure 1 is a perspective view of the secondary battery 100 related to the present embodiment, which is an example of the secondary battery of the present disclosure. Figure 2 is a perspective view in which the secondary battery 100 of Figure 1 is upside down. Figure 3 shows the internal structure of the secondary battery 100 of Figure 1 Also, in the following description, the reference numerals L, R, F, Rr, U, D in the drawings indicate left, right, front, rear, up, and down, and the reference numerals X, Y, Z in the drawings respectively indicate the short side direction, the long side direction orthogonal to the short side direction, and the up-down direction orthogonal to the short side direction and the long side direction of the secondary battery 100.

[0021] ​​​In the drawings, U (upper) and D (lower) correspond to the upper and lower positions of the secondary battery 100 in its normal usage configuration (particularly, in an on-vehicle battery installation). However, the usage configuration of the secondary battery 100 is not limited to this. For example, in other embodiments, the secondary battery 100 may be installed upside down.

[0022] The secondary battery 100 involved in this embodiment is a lithium-ion secondary battery. As a result, the secondary battery 100 can have excellent battery characteristics such as high energy density and high capacity. However, in other embodiments, the secondary battery can also be a secondary battery other than a lithium-ion secondary battery (such as a sodium-ion secondary battery).

[0023] like Figures 1 to 3 As shown, the secondary battery 100 includes a battery case 10 and an electrode assembly 20. The secondary battery 100 also includes a positive electrode terminal 30, a negative electrode terminal 40, an insulating sheet 50, and an electrolyte solution (not shown).

[0024] Battery Case

[0025] The battery case 10 is a frame that contains the electrode body 20 and the electrolyte. Figure 1 as well as Figure 2 As shown, the battery case 10 has a flat, bottomed rectangular parallelepiped shape. In other words, the battery case 10 is square. Therefore, the secondary battery 100 shown in the figure is a square lithium-ion secondary battery. However, the shape of the battery case 10 is not limited to this. To improve space efficiency when constructing a battery module using multiple secondary batteries 100, the battery case 10 is preferably square.

[0026] The material of the battery case 10 can be the same as that used in the past (e.g., metal, resin, etc.) and is not particularly limited. From the perspectives of strength and thermal conductivity, the material of the battery case 10 is preferably metal, more preferably aluminum, an aluminum alloy, iron, or an iron alloy. Alternatively, the battery case 10 may be made of a laminated film.

[0027] like Figures 1 to 3 As shown in FIG. 1 , the battery case 10 includes a case body 12, a first sealing plate 14, and a second sealing plate 16. The case body 12 is in the shape of a square cylinder. Figure 3 As shown, the housing body 12 has a first opening 12e at one end and a second opening 12f at the other end. The first sealing plate 14 seals the first opening 12e, and the second sealing plate 16 seals the second opening 12f. The battery housing 10 is integrated by joining the first sealing plate 14 and the second sealing plate 16 to the housing body 12 at the first opening 12e and the second opening 12f, respectively (e.g., by welding). The battery housing 10 is hermetically sealed. Therefore, the secondary battery 100 is a sealed battery.

[0028] The battery case 10 has a pair of first surfaces, a pair of second surfaces, and a pair of third surfaces. Figure 1 As shown, the shell body 12 includes: a roughly rectangular bottom surface 12a; a pair of long side surfaces 12b extending from the long sides of the bottom surface 12a and facing each other; and a top surface 12c connecting the upper ends of the pair of long side surfaces 12b. The top surface 12c is roughly rectangular. The top surface 12c faces the bottom surface 12a. Here, the top surface 12c and the bottom surface 12a are a pair of first surfaces, and the pair of long side surfaces 12b are a pair of second surfaces. In addition, the area of ​​the long side surfaces 12b is preferably larger than the area of ​​the bottom surface 12a and larger than the area of ​​the top surface 12c. For example, the bottom surface 12a and the top surface 12c can constitute a pair of short side surfaces. The shell body 12 is formed, for example, by bending a metal plate into a cylindrical shape and joining the seams (for example, welding). In the example shown in the figure, the welded joint 12d is located on the top surface 12c. In addition, the welded joint 12d can also be located on the bottom surface 12a or on the long side surfaces 12b.

[0029] like Figure 2 As shown, a gas discharge valve 13 is provided on the bottom surface 12a of the shell body 12. The gas discharge valve 13 is configured to rupture when the pressure in the battery shell 10 reaches a predetermined value or more, thereby discharging the gas in the battery shell 10 to the outside. In addition, in the present embodiment, the number of gas discharge valves 13 is one, but it may be two or more. In addition, in the present embodiment, the gas discharge valve 13 is provided on the bottom surface 12a, but is not limited thereto. In other embodiments, the gas discharge valve 13 may also be provided on a surface other than the bottom surface 12a, such as the long side surface 12b, the top surface 12c, the sealing plate 14, etc. Alternatively, in other embodiments, the secondary battery 100 may be provided upside down with respect to the accompanying drawings, and the bottom surface 12a may be changed to the top surface 12c so that the gas discharge valve faces upward. In addition, the area of ​​the gas discharge valve 13 is arbitrary.

[0030] In this embodiment, the gas discharge valve 13 is a cross-shaped cutout, but the shape of the gas discharge valve 13 is not particularly limited. In other embodiments, the gas discharge valve 13 may also be a linear cutout (only vertical or horizontal lines), or may be a conventionally known oval valve (with a cutout therein) or circular valve (with a cutout therein). The dimensions of the cutout (e.g., length, depth, etc.) are arbitrary and can be appropriately determined, for example, based on the pressure resistance of the battery case 10.

[0031] The first sealing plate 14 and the second sealing plate 16 are plate-shaped members that seal the first opening 12e and the second opening 12f of the housing body 12. The first sealing plate 14 and the second sealing plate 16 are generally rectangular in a plan view. Here, the first sealing plate 14 and the second sealing plate 16 constitute a pair of third surfaces.

[0032] The first sealing plate 14 is provided with a liquid injection hole 17. The liquid injection hole 17 is used to inject electrolyte into the inside of the battery case 10 after the first sealing plate 14 and the second sealing plate 16 are installed to the case main body 12. The liquid injection hole 17 is provided below the positive electrode terminal 30, but the position of the liquid injection hole 17 provided to the first sealing plate 14 is not limited to this. The liquid injection hole 17 is sealed by a sealing member 18 after the electrolyte is injected. In addition, in the present embodiment, the liquid injection hole 17 is provided to the first sealing plate 14, but the liquid injection hole 17 can also be provided to the second sealing plate 16, and can also be provided to the case main body 12. In addition, in the present embodiment, the liquid injection hole 17 is provided to a different face from the gas discharge valve 13, but the liquid injection hole 17 can also be provided to the same face as the gas discharge valve 13.

[0033] < Electrode terminal >

[0034] The positive electrode terminal 30 and the negative electrode terminal 40 are respectively fixed to the battery case 10. Here, the positive electrode terminal 30 and the negative electrode terminal 40 are respectively fixed to facing surfaces of the battery case 10. In detail, the positive electrode terminal 30 is installed to the first sealing plate 14, and the negative electrode terminal 40 is installed to the second sealing plate 16.

[0035] In detail, the first sealing plate 14 and the second sealing plate 16 have through holes in which insulating members 63, 64 are respectively installed. The positive electrode terminal 30 is installed to the first sealing plate 14 via the insulating member 63, and the positive electrode terminal 30 is insulated from the first sealing plate 14. The negative electrode terminal 40 is installed to the second sealing plate 16 via the insulating member 64, and the negative electrode terminal 40 is insulated from the second sealing plate 16. In addition, the insulating member 63 insulates the first sealing plate 14 from the electrode body 20 inside the battery case 10. The insulating member 64 insulates the second sealing plate 16 from the electrode body 20 inside the battery case 10.

[0036] In addition, in the present embodiment, the positive electrode terminal 30 and the negative electrode terminal 40 are respectively provided to the first sealing plate 14 and the second sealing plate 16, but the arrangement of the positive electrode terminal 30 and the negative electrode terminal 40 is not limited to this. In other embodiments, it can also be that both the positive electrode terminal 30 and the negative electrode terminal 40 are provided to one of the first sealing plate 14 or the second sealing plate 16. The positive electrode terminal 30 and the negative electrode terminal 40 can also be provided to the case main body 12. In addition, in the present embodiment, the positive electrode terminal 30 and the negative electrode terminal 40 are provided to different faces from the gas discharge valve 13, but the positive electrode terminal 30 and the negative electrode terminal 40 can also be provided to the same face as the gas discharge valve 13.

[0037] However, in the case where the positive terminal 30 and the negative terminal 40 are provided to the first sealing plate 14 and the second sealing plate 16, respectively, as in the present embodiment, the height (i.e., the size in the Z direction of the drawing) of the secondary battery 100 can be reduced, and a battery having a high volumetric energy density can be easily obtained. In this case, a battery module having a high volumetric energy density can be easily configured, particularly for vehicle use.

[0038] The positive terminal 30 and the negative terminal 40 are exposed on the surface outside the first sealing plate 14 and the second sealing plate 16, respectively. Here, the positive terminal 30 and the negative terminal 40 are disposed on an axis extending in the long side direction Y and passing through the center of the first sealing plate 14 and the second sealing plate 16. However, in other embodiments, the axis can be offset from the center of the first sealing plate 14 and the second sealing plate 16, for example, in the short side direction X. In addition, the positive terminal 30 and the negative terminal 40 can not be disposed on the axis. For example, one of the positive terminal 30 and the negative terminal 40 can be biased to one side in the short side direction X, and the other can be biased to the other side in the short side direction X.

[0039] The positive terminal 30 is preferably made of metal, and more preferably composed of aluminum or an aluminum alloy. The negative terminal 40 is preferably made of metal, and more preferably composed of copper or a copper alloy.

[0040] The electrode body 20 has a positive electrode current collector tab electrically connected to the positive electrode 23 at one end portion, and the positive electrode current collector tab is collectively attached to the positive electrode current collector member 32. The electrode body 20 has a negative electrode current collector tab electrically connected to the negative electrode 24 at the other end portion, and the negative electrode current collector tab is collectively attached to the negative electrode current collector member 42. Inside the battery case 10, the positive electrode current collector member 32 is attached to the first sealing plate 14 and electrically connected to the positive terminal 30. Inside the battery case 10, the negative electrode current collector member 42 is attached to the second sealing plate 16 and electrically connected to the negative terminal 40.

[0041] In this way, the positive terminal 30 is electrically connected to the positive electrode 23 of the electrode body 20 via the positive electrode current collector tab and the positive electrode current collector member 32 inside the battery case 10. The negative terminal 40 is electrically connected to the negative electrode 24 of the electrode body 20 via the negative electrode current collector tab and the negative electrode current collector member 42 inside the battery case 10. In addition, the structure in which the positive terminal 30 and the negative terminal 40 are electrically connected to the positive electrode 23 and the negative electrode 24 of the electrode body 20 is not limited to the configuration illustrated.

[0042] < Electrode Body >

[0043] The electrode body 20 is housed inside the battery case 10. Figure 4 is a perspective view of the secondary battery 100, and is a diagram schematically showing the case main body 12 in perspective. Figure 5is a schematic cross-sectional view of the electrode body 20 along the thickness direction of the electrode body 20. Figure 6 is a cross-sectional view of the electrode body 20 schematically showing the internal structure of the battery case 10 in a simplified manner, and is along the X direction (the thickness direction of the electrode body 20, in other words, the stacking direction of the positive electrode 23 and the negative electrode 24) and the Z direction in Figure 1 Figure 6 is a cross-sectional view of the section parallel to the first opening 12e of the case main body 12.

[0044] As shown in Figure 4 and Figure 6 , the electrode body 20 is disposed in the inside of the battery case 10 in a state covered by the insulating sheet 50 described later. In the present embodiment, a plurality of electrode bodies 20 are housed in the inside of one battery case 10. In the example shown in Figure 4 and Figure 6 , two electrode bodies 20 are housed in the inside of one battery case 10. In the case where the electrode bodies 20 are plural as such, a flow path of electrolytic solution or gas generation can be formed between the electrode body 20 and the electrode body 20 adjacent thereto. In addition, the number of electrode bodies 20 housed in the inside of one battery case 10 is not particularly limited. In other embodiments, the number of electrode bodies 20 housed in the inside of one battery case 10 can be three or more, and can also be one.

[0045] The electrode body 20 has a plurality of negative electrodes 24 (negative electrode plates 24) as first electrode plates, a plurality of positive electrodes 23 (positive electrode plates 23) as second electrode plates different in polarity from the first electrode plates, and one separator 25. Thus, in the present embodiment, the electrode body 20 is a stacked electrode body, and the positive electrodes 23 and the negative electrodes 24 are alternately stacked. The one separator 25 is disposed between the plurality of positive electrodes 23 and the plurality of negative electrodes 24, thereby insulating the positive electrodes 23 and the negative electrodes 24. In other embodiments, the second electrode plates can be negative electrodes 24 and the first electrode plates can be positive electrodes 23. The electrode body 20 is a stacked electrode body, and has high impregnation properties of electrolytic solution compared to a wound electrode body, and is particularly advantageous in terms of injection properties of electrolytic solution at the time of manufacture. In addition, according to the stacked electrode body, it is easy to configure a battery having a high volumetric energy density.

[0046] In Figure 5 ​In the illustrated example, the number of pieces of the positive electrode 23 is two, and the number of pieces of the negative electrode 24 is three. However, the number of pieces of the positive electrode 23 and the number of pieces of the negative electrode 24 are not particularly limited, and can be appropriately determined in accordance with the design of the battery. In the illustrated example, the number of pieces of the negative electrode 24 is one more than the number of pieces of the positive electrode 23. Thus, in the electrode layer-stacked structure of the positive electrode 23 and the negative electrode 24, the outermost layer is the negative electrode 24. In this case, the lithium contained in the positive electrode active material of the positive electrode 23 can be effectively utilized, and the precipitation of lithium at the negative electrode 24 can be highly prevented. In other embodiments, the number of pieces of the positive electrode 23 and the number of pieces of the negative electrode 24 can be the same, or the number of pieces of the positive electrode 23 can be more than the number of pieces of the negative electrode 24. In addition, for example, the number of pieces of the positive electrode 23 and the number of pieces of the negative electrode 24 can each be 20 or more.

[0047] In the present embodiment, the size of the negative electrode 24 is larger than the size of the positive electrode 23. In Figure 5 In the present embodiment, the size of the negative electrode 24 is larger than the size of the positive electrode 23. In

[0048] The electrode body 20 has a substantially rectangular parallelepiped shape. As Figure 3 In addition, as Figure 4 The electrode body 20 has a first side surface 20a facing the bottom surface 12a of the case main body 12. The electrode body 20 has a second side surface 20c facing the top surface 12c of the case main body 12. The first side surface 20a and the second side surface 20c are a pair of side surfaces facing each other. In addition to this, the electrode body 20 has a pair of main surfaces facing the pair of long side surfaces 12b of the case main body 12. The electrode body 20 has a pair of side surfaces facing the first seal plate 14 and the second seal plate 16.

[0049] The separator 25 is in a band shape. That is, the separator 25 is in a long strip shape. The separator 25 has a multi-folded portion 25a in which the separator 25 is folded in a multi-folded shape in a manner in which the separator 25 is disposed between the positive electrode 23 and the negative electrode 24. In the multi-folded portion 25a, the separator 25 is alternately folded back at the end portion of the positive electrode 23 and at the end portion of the negative electrode 24. Thus, the multi-folded portion 25a has a first folded portion 25aa in which the separator 25 is folded back at the end portion of the negative electrode 24 and a second folded portion 25ab in which the separator 25 is folded back at the end portion of the positive electrode 23. The first folded portion 25aa is disposed on one side in a direction perpendicular to the stacking direction of the positive electrode 23 and the negative electrode 24, and the second folded portion 25ab is disposed on the other side in the direction perpendicular to the stacking direction of the positive electrode 23 and the negative electrode 24. In the illustrated example, the first folded portion 25aa faces the bottom surface 12a of the case main body 12, and the second folded portion 25ab faces the top surface 12c of the case main body 12. However, the first folded portion 25aa can face the top surface 12c of the case main body 12, and the second folded portion 25ab can face the bottom surface 12a of the case main body 12.

[0050] In the illustrated example, the first folded portion 25aa is separated from the end surface of the negative electrode 24. Thus, there is a distance between the end surface of the negative electrode 24 and the first folded portion 25aa. However, the first folded portion 25aa can be in contact with the end surface of the negative electrode 24 along the end portion of the negative electrode 24.

[0051] Similarly, in the illustrated example, the second folded portion 25ab is separated from the end surface of the positive electrode 23. Thus, there is a distance between the end surface of the positive electrode 23 and the second folded portion 25ab. However, the second folded portion 25ab can be in contact with the end surface of the positive electrode 23 along the end portion of the positive electrode 23.

[0052] In addition, the multi-folded portion 25a has a flat portion 25ac that is sandwiched by the positive electrode 23 and the negative electrode 24. In addition, the outermost surface of the negative electrode 24 that is the outermost layer of the multi-folded portion 25a also has the flat portion 25ac. In this way, the plurality of positive electrodes 23 are each sandwiched by the flat portion 25ac of the separator 25, and the plurality of negative electrodes 24 are each sandwiched by the flat portion 25ac of the separator 25. Thus, the adjacent positive electrode 23 and negative electrode 24 are insulated by the flat portion 25ac. In addition, not all of the positive electrodes 23 and the negative electrodes 24 can be sandwiched by the flat portion 25ac of the multi-folded portion 25a. For example, the multi-fold can be formed in a state in which the separator 25 is sandwiched between the positive electrode 23 and the negative electrode 24, and the flat portion 25ac of the outermost surface of the negative electrode 24 that is the outermost layer of the multi-folded portion 25a can not be provided. However, from the viewpoint of protecting the negative electrode 24, it is preferable that the outermost surface of the negative electrode 24 that is the outermost layer of the multi-folded portion 25a be covered by the flat portion 25ac. By folding the separator 25 in a multi-folded shape, the manufacturing efficiency of the stacked electrode body can be improved.

[0053] Further, the separator 25 has a winding portion 25b wound around the outer periphery of the portion in which the positive electrode 23, the negative electrode 24, and the multi-fold portion 25a (more specifically, the flat portion 25ac) are laminated. With the winding portion 25b, in the electrode lamination structure of the positive electrode 23 and the negative electrode 24, the outermost surface of the electrode on the outermost layer and the outermost surface of the electrode on the other layer are reliably covered by the separator 25. Thus, the mixing of foreign matter into the electrode body 20 and the generation of foreign matter in the electrode body 20 can be suppressed.

[0054] Further, the separator 25 has a first end portion 25c which is an end portion on one side in the longitudinal direction of the separator 25, and a second end portion 25d which is an end portion on the other side. The first end portion 25c is a start end portion, and thus, is located inside (in other words, on the inner peripheral side) of the winding portion 25b, in continuation to the multi-fold portion 25a. The second end portion 25d is an end end portion, and thus, is located at the end of winding of the winding portion 25b.

[0055] The position of the second end portion 25d as the end end portion is not particularly limited. The second end portion 25d can be located on the main surface of the electrode plate on the outermost layer of the electrode lamination structure of the positive electrode 23 and the negative electrode 24 (the negative electrode 24 in the illustrated example), as in the illustrated example, or can be located on the side surface of the electrode lamination structure. The second end portion 25d as the end end portion is preferably fixed by a tape. In the illustrated example, the second end portion 25d is fixed by a winding termination tape 26. Further, the second end portion 25d can be fixed to a portion of the separator 25 on the inner peripheral side by an adhesive, pressure bonding, heat fusion, or the like.

[0056] As shown in FIG. 1, the electrode body 20 is configured to have the positive electrode 23 and the negative electrode 24 laminated in the stacking direction. The positive electrode 23 and the negative electrode 24 are laminated in the stacking direction by the separator 25 interposed therebetween. The positive electrode 23 and the negative electrode 24 are laminated in the stacking direction by the separator 25 interposed therebetween. Figure 6 As shown in FIG. 1, the electrode body 20 is configured to have the positive electrode 23 and the negative electrode 24 laminated in the stacking direction. The positive electrode 23 and the negative electrode 24 are laminated in the stacking direction by the separator 25 interposed therebetween. The positive electrode 23 and the negative electrode 24 are laminated in the stacking direction by the separator 25 interposed therebetween.

[0057] As shown in FIG. 1, the electrode body 20 is configured to have the positive electrode 23 and the negative electrode 24 laminated in the stacking direction. The positive electrode 23 and the negative electrode 24 are laminated in the stacking direction by the separator 25 interposed therebetween. The positive electrode 23 and the negative electrode 24 are laminated in the stacking direction by the separator 25 interposed therebetween. Figure 5 As shown in FIG. 1, the electrode body 20 is configured to have the positive electrode 23 and the negative electrode 24 laminated in the stacking direction. The positive electrode 23 and the negative electrode 24 are laminated in the stacking direction by the separator 25 interposed therebetween. The positive electrode 23 and the negative electrode 24 are laminated in the stacking direction by the separator 25 interposed therebetween.

[0058] Here, the longer the extension portion 25e is, the more the end portion of the electrode can be protected. Specifically, as shown in FIG. 1, the extension portion 25e is preferably longer than the multi-fold portion 25a. Figure 5The thickness of the electrode body 20 is set to T as shown. The length of the extension 25e of the separator 25 in the stacking direction of the positive electrode 23 and the negative electrode 24 is set to L. The ratio of L to T (L / T) is preferably 0.1 to 0.9, more preferably 0.1 to 0.7, and further preferably 0.2 to 0.6. In addition, the thickness T of the electrode body 20 is the distance between the layers of the separator 25 that is the outermost layer in the stacking direction of the positive electrode 23 and the negative electrode 24. Thus, the thickness T of the electrode body 20 does not include the thickness of the winding termination tape 26.

[0059] The extension 25e of the separator 25 preferably covers at least one second bent portion 25ab. The extension 25e of the separator 25 preferably faces the end surface of at least one negative electrode 24. In addition, the number of stacked pieces of the negative electrode 24 in the electrode body 20 is set to N. The extension 25e of the separator 25 preferably faces the end surface of 0.1 N or more pieces of the negative electrode 24, and more preferably faces the end surface of 0.2 N or more pieces of the negative electrode 24. In addition, the extension 25e of the separator 25 preferably faces the end surface of 5 or more pieces of the negative electrode 24 (in other words, the extension 25e of the separator 25 preferably covers at least five second bent portions 25ab). On the other hand, the extension 25e of the separator 25 preferably faces the end surface of 0.9 N or less pieces of the negative electrode 24, and more preferably faces the end surface of 0.7 N or less pieces of the negative electrode 24. In addition, for example, in the case where the number of stacked pieces of the negative electrode 24 is 20 pieces (i.e., N = 20), 0.1 N is 2 pieces.

[0060] The position of the first end portion 25c as the start end portion is generally determined in accordance with the length of the extension 25e of the separator 25. In the example shown in FIG. 1, the first end portion 25c is located at the side surface of the electrode stacking structure of the positive electrode 23 and the negative electrode 24. However, the first end portion 25c can also be located on the main surface of the electrode that is the outermost layer of the electrode stacking structure. In this case, the extension 25e of the separator 25 covers all of the second bent portion 25ab (i.e., covers the side surface of the electrode stacking structure of the positive electrode 23 and the negative electrode 24), and further covers at least a portion of the main surface of the outermost negative electrode 24 (i.e., the outermost negative electrode 24 on the right side in FIG. 1, and the outermost negative electrode 24 on the opposite side of the negative electrode 24 at which the folding starts). Figure 5 Figure 5 In the example shown in FIG. 1, the first end portion 25c is located at the side surface of the electrode stacking structure of the positive electrode 23 and the negative electrode 24. However, the first end portion 25c can also be located on the main surface of the electrode that is the outermost layer of the electrode stacking structure. In this case, the extension 25e of the separator 25 covers all of the second bent portion 25ab (i.e., covers the side surface of the electrode stacking structure of the positive electrode 23 and the negative electrode 24), and further covers at least a portion of the main surface of the outermost negative electrode 24 (i.e., the outermost negative electrode 24 on the right side in FIG. 1, and the outermost negative electrode 24 on the opposite side of the negative electrode 24 at which the folding starts).

[0061] The separator 25 is porous as described later, and thus can hold an electrolyte solution in the pores. In the example shown in the drawing, the extension 25e of the separator 25 is on the top surface 12c side of the case main body 12 (i.e., the upper side in the usual state of use). Thus, the electrolyte solution can be held by the extension 25e of the separator 25 over the positive electrode 23 and the negative electrode 24 of the electrode body 20. Thus, when the extension 25e of the separator 25 is long, it is advantageous in terms of supplying the electrolyte solution to the upper portion of the electrode body 20.

[0062] ​The first end portion 25c as the start end portion can not be fixed by the tape or the like since it is located inside the winding portion 25b. The tape creates a step on the electrode body 20, which can cause lithium to be precipitated. In the case where the first end portion 25c is not fixed by the tape, lithium precipitation can be suppressed. For example, the first end portion 25c is fixed by being sandwiched by the positive electrode 23, the negative electrode 24, and the stacking portion and the winding portion 25b of the multi-fold portion 25a. Alternatively, for example, in the case where the separator 25 has an adhesive layer, the first end portion 25c is fixed by the adhesive layer.

[0063] Likewise, the extension portion 25e of the separator 25 can not be fixed by the tape or the like. In the case where the extension portion 25e is not fixed by the tape, lithium precipitation can be suppressed. For example, the extension portion 25e is fixed by being sandwiched by the positive electrode 23, the negative electrode 24, and the stacking portion and the winding portion 25b of the multi-fold portion 25a. Alternatively, for example, in the case where the separator 25 has an adhesive layer, the extension portion 25e is fixed by the adhesive layer.

[0064] In the present embodiment, in the stacking direction of the positive electrode 23 and the negative electrode 24 (the Z direction of the drawing), the outer surface of the electrode located on one of the outermost surface sides among the positive electrode 23 and the negative electrode 24 is covered by the separator 25, and the outer surface of the electrode located on the other of the outermost surface sides is also covered by the separator 25. That is, in the electrode body 20, in the electrode stacking structure of the positive electrode 23 and the negative electrode 24, the outer surfaces of the two outermost layers are covered by the separator 25. These outer surfaces are typically covered at least by the winding portion 25b of the separator 25. In the illustrated example, in the electrode stacking structure, the two outermost layers are the negative electrodes 24. The negative electrode 24 located on one of the sides of the start of the multi-folding of the separator 25 (the negative electrode 24 on the left side of the drawing) is covered by the flat portion 25ac and the winding portion 25b of the separator 25. The negative electrode 24 located on the other of the sides (the negative electrode 24 on the right side of the drawing) is covered by the winding portion 25b of the separator 25. Figure 5 Figure 5 Thus, by the outer surfaces of the two outermost layers of the electrodes being covered by the separator 25, damage to the two outermost layers of the electrodes due to impact, vibration, or the like during manufacturing can be suppressed.

[0065] The electrode body 20 is preferably such that the surface other than the surface on which the electrode current collector tabs (i.e., the positive electrode current collector tab and the negative electrode current collector tab) protrude is covered by the separator 25. Also, in the surface on which the electrode current collector tabs protrude, the portion other than the electrode current collector tabs can be covered by the separator 25.

[0066] ​In the example shown in the figure, a diaphragm overlapping portion 25ba is provided on the outside of the first bent portion 25aa of the diaphragm 25, in which the winding portion 25b overlaps with more than two layers (that is, the diaphragm layer of the winding portion 25b overlaps with more than two layers). Here, in a lithium-ion secondary battery, the negative electrode is more susceptible to damage than the positive electrode. In addition, the negative electrode is susceptible to damage at the end, especially the corner portion of the end of the negative electrode active material layer. Furthermore, in the example shown in the figure, as described above, the size of the negative electrode 24 is larger than that of the positive electrode 23, and therefore, the end of the negative electrode 24 protrudes from the side of the laminate of the positive electrode 23 and the negative electrode 24. Therefore, the end of the negative electrode 24 is protected by the diaphragm 25 having a total of more than three layers, which can more effectively suppress damage to the negative electrode 24 (especially the end of the negative electrode 24). Therefore, it is preferred to provide the diaphragm overlapping portion 25ba as described above.

[0067] In the illustrated example, because the end of the negative electrode 24 is designed to be easily damaged, the separator overlap portion 25ba is provided outside the first bent portion 25aa, which is folded back at the end of the negative electrode 24. However, the separator overlap portion 25ba can also be provided outside the second bent portion 25ab, which is folded back at the end of the positive electrode 23 (outside the extension portion 25e). In this case, damage to the end of the positive electrode 23 can be suppressed. However, since the second bent portion 25ab of the separator 25 can be protected by the extension portion 25e, and the first bent portion of the separator 25 can be protected by the wrapping portion 25b, arranging the wrapping portion 25b outside the first bent portion 25aa is advantageous from the perspective of protecting the entire electrode body 20.

[0068] In the example shown in the figure, as described above, the number of negative electrodes 24 is one more than the number of positive electrodes 23. Therefore, in the electrode stack structure of the positive electrodes 23 and the negative electrodes 24, the outermost layer is the negative electrode 24. Therefore, here, the negative electrode 24 located on the outermost surface in the stacking direction of the positive electrodes 23 and the negative electrodes 24 is called the outermost negative electrode. Figure 3 The outermost negative electrode 24 on the right side. The outermost negative electrode is arranged between the multi-fold portion 25a and the winding portion 25b. When the separator 25 has a substrate and a heat-resistant layer located on the main surface of the substrate on the positive electrode 23 side (in this case, an adhesive layer may be further provided on the heat-resistant layer), the positive electrode 23 is in contact with the heat-resistant layer, and the negative electrode is in contact with the substrate. When the outermost negative electrode is arranged between the multi-fold portion 25a and the winding portion 25b, the substrate of the separator 25 is exposed on the outer surface of the electrode body 20 (in other words, the exposed surface). In this way, when the substrate of the separator 25 is exposed on the outer surface of the electrode body 20, the heat-resistant layer of the separator 25 can be protected by the substrate, which is advantageous.

[0069] like Figure 6As shown, in the electrode body 20, the negative electrode current collector tab is located at the center of the negative electrode 24 in the direction (Z direction of the drawing) in which the first bent portion 25aa and the second bent portion 25ab of the separator 25 are connected. However, the negative electrode current collector tab can be biased in the direction away from the separator overlap portion 25ba in the direction (Z direction of the drawing) in which the first bent portion 25aa and the second bent portion 25ab of the separator 25 are connected. That is, the negative electrode current collector tab can be biased toward the side closer to the top surface 12c of the case main body 12 than the bottom surface 12a of the case main body 12.

[0070] Also, in the electrode body 20, the positive electrode current collector tab is located at the center of the positive electrode 23 in the direction (Z direction of the drawing) in which the first bent portion 25aa and the second bent portion 25ab of the separator 25 are connected. However, the positive electrode current collector tab can be biased in the direction away from the separator overlap portion 25ba in the direction (Z direction of the drawing) in which the first bent portion 25aa and the second bent portion 25ab of the separator 25 are connected. That is, the positive electrode current collector tab can be biased toward the side closer to the top surface 12c of the case main body 12 than the bottom surface 12a of the case main body 12.

[0071] Here, Figure 6 is a cross-sectional view parallel to the first opening 12e of the case main body 12. In the cross section parallel to the first opening 12e of the case main body 12, the internal dimension of the case main body 12 in the direction (Z direction of the drawing) in which the negative electrode 24 of the case main body 12 extends, that is, Figure 4 is set to D1, and the dimension of the negative electrode 24 along the internal dimension D1 is set to W1. D1 and W1 preferably satisfy W1 / D1 > 0.9, and more preferably satisfy W1 / D1 > 0.95. By making W1 / D1 greater than 0.9 (particularly, greater than 0.95), the large movement of the electrode body 20 in the inside of the battery case 10 can be suppressed, and the electrode damage in the case where the secondary battery 100 is subjected to vibration or impact can be further suppressed.

[0072] <Insulating sheet>

[0073] As Figure 6 and Figure 7 shown, the insulating sheet 50 is housed in the inside of the battery case 10 together with the electrode body 20. The insulating sheet 50 is disposed between the battery case 10 and the electrode body 20. As in the illustrated example, the insulating sheet 50 is preferably disposed at least on the outer surface side of the overlap portion 25ba of the separator 25. Thereby, the damage of the electrode (the negative electrode 24 in the illustrated example) can be further suppressed. Thus, even in the case where the weight of the electrode body of the secondary battery 100 is large, the electrode damage due to impact, vibration, or the like can be suppressed at a high level. In the illustrated example, the insulating sheet 50 covers the periphery of the electrode body 20 (the four outer surfaces facing the inner surface of the case main body 12). Thus, the insulating sheet 50 has a portion disposed on the outer surface side of the separator overlap portion 25ba.

[0074] The insulating sheet 50 is made of an insulating material, preferably a resin. As examples of the resin, there can be mentioned: olefin-based resins such as polyethylene (PE), polypropylene (PP), polymethylpentene (PMP / TPX (trademark)), and the like; polyester-based resins such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and the like; acrylic resins (PMMA); polyimide (PI); polyphenylene ether (PPE); triacetate (TAC); polyphenylene sulfide resin (PPS); polycarbonate (PC); nylon; fluororesins such as polytetrafluoroethylene (PTFE), and the like. Of these, PE and PP are preferred. In addition, the thickness of the insulating sheet 50 is preferably greater than the thickness of the separator 25.

[0075] Figure 8 An expanded view of the insulating sheet 50 is shown. Figure 8 is a view of the insulating sheet 50 as viewed from the direction of the bottom surface 12a of the battery case 10. In the present embodiment, the insulating sheet 50 is made of one sheet-like member. By bending this sheet-like member in a manner corresponding to the shape of the electrode body 20 to form a square tube, the insulating sheet 50 is constituted. As shown in Figure 8 and Figure 8 At both end portions 50a in the circumferential direction of the electrode body 20, there is an overlapping portion 50b in which the bent sheet end portions 50a overlap. In the insulating sheet 50, at this overlapping portion 50b, the bent sheet end portions 50a are fixed to each other by joining or the like. In the example shown in Figure 8 , the sheet end portions 50a are fixed to each other using an adhesive tape 52. The method of fixation is not limited to the method using the adhesive tape 52, and can be fusion by heat fusion or ultrasonic welding, adhesion by an adhesive, or the like.

[0076] As shown in ​ , at the overlapping portion 50b of the insulating sheet 50, both end portions 50a of the bent sheet can be fixed only at a portion thereof. In ​ , the sheet end portions 50a are fixed to each other at two points in the vicinity of both end portions of the overlapping portion 50b. The number of points of fixation is not limited thereto. For example, the two end portions and the central portion of the overlapping portion 50b can be fixed in total at three points. Alternatively, the sheet end portions 50a can be fixed to each other over the entire length of the overlapping portion 50b.

[0077] In the illustrated example, the overlapping portion 50b of the insulating sheet 50 is disposed outside the separator overlapping portion 25ba. For example, at least a portion of the overlapping portion 50b of the insulating sheet 50 faces a portion of the separator overlapping portion 25ba. In this case, there are at least two layers of the insulating sheet 50 at the overlapping portion 50b, and thus the end portion of the electrode on the inner side of the separator overlapping portion 25ba can be protected at a higher level. Thus, damage to the end portion of the electrode on the inner side of the separator overlapping portion 25ba can be more effectively suppressed. Note that the position of the overlapping portion 50b of the insulating sheet 50 is not limited thereto, and the overlapping portion 50b of the insulating sheet 50 can be at a position that does not face the separator overlapping portion 25ba.

[0078] In the illustrated example, at the overlapping portion 50b of the insulating sheet 50, there is a region through which the electrolyte and the gas can pass. In this case, it is advantageous from the viewpoint of high impregnation of the electrolyte into the electrode body 20 and rapid discharge of the gas from the electrode body 20. The region through which the electrolyte and the gas can pass can be provided by joining only a portion of the overlapping portion 50b. That is, the portion of the overlapping portion 50b that is not joined becomes the region through which the electrolyte and the gas can pass. Alternatively, the region through which the electrolyte and the gas can pass can be provided by joining throughout the entire length of the overlapping portion 50b and providing a through hole or the like in the insulating sheet. In the case where the entire length of the overlapping portion is L in the elongation direction of the overlapping portion 50b, the region through which the electrolyte and the gas can pass in the overlapping portion 50b preferably has a size of 1 / 5L or more, more preferably 1 / 3L or more, and further preferably 1 / 2L or more. The region through which the electrolyte and the gas can pass at the overlapping portion 50b of the insulating sheet 50 can be always open, or can be a region that opens after being stressed.

[0079] In the illustrated example, the bottom surface 12a of the case main body 12 of the battery case 10 faces the overlapping portion 50b of the insulating sheet 50. That is, the overlapping portion 50b of the insulating sheet 50 is on the side of the bottom surface 12a of the case main body 12 of the battery case 10. Thus, the remaining liquid of the electrolyte that is not impregnated in the electrode body 20 exists on the side of the bottom surface 12a of the case main body 12 in the battery case 10, and thus it is advantageous in terms of supplying this remaining liquid to the electrode body 20 in the case where the overlapping portion 50b faces the bottom surface 12a. Thus, in the present embodiment, the overlapping portion 50b of the insulating sheet 50 is preferably on the side where the remaining liquid of the electrolyte exists. At this time, it is more advantageous if there is a region through which the electrolyte can pass at the overlapping portion 50b of the insulating sheet 50. Note that in the illustrated example, the overlapping portion 25ba of the separator 25 also faces the bottom surface 12a of the case main body 12 of the battery case 10. Thus, the reduction in the impregnation of the electrolyte into the electrode body 20 due to the three or more separator layers in the overlapping portion 25ba can be reduced or eliminated. Note that the overlapping portion 50b of the insulating sheet 50 can also face a surface of the case main body 12 of the battery case 10 other than the bottom surface 12a.

[0080] In the illustrated example, the bottom surface 12a of the case main body 12 of the battery case 10 has a gas discharge valve 13. Thus, the gas discharge valve 13 is provided on a surface facing the overlapping portion 25ba of the separator 25. In addition, the gas discharge valve 13 is provided on a surface of the battery case 10 facing the overlapping portion 50b of the insulating sheet 50. In this case, when gas is generated abruptly in the electrode body 20, the gas is easily discharged to the outside of the battery case 10 via the gas discharge valve 13. At this time, it is more advantageous if there is a region through which gas can pass in the overlapping portion 50b of the insulating sheet 50. In addition, the overlapping portion 50b of the insulating sheet 50 can face a surface of the case main body 12 of the battery case 10 that does not have the gas discharge valve 13.

[0081] Next, the materials that constitute the positive electrode 23, the negative electrode 24, and the separator 25 will be described. Typically, the positive electrode 23 has a positive electrode current collector and a positive electrode active material layer fixed to at least one surface of the positive electrode current collector. The positive electrode current collector is composed of, for example, an electrically conductive metal such as aluminum, an aluminum alloy, nickel, stainless steel, or the like. Here, the positive electrode current collector is a metal foil, specifically an aluminum foil. In the present embodiment, in the positive electrode 23, a portion where the positive electrode active material layer is not formed so that the positive electrode current collector is exposed is formed, and this exposed portion constitutes a current collector tab. However, the method of constituting the current collector tab is not limited thereto.

[0082] The positive electrode active material layer contains a positive electrode active material that can reversibly adsorb and release a charge carrier. As the positive electrode active material, an oxide containing at least one of Ni, Co, and Mn is preferable, and as examples thereof, lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel-manganese composite oxide, lithium nickel-cobalt-manganese composite oxide, and the like can be listed. The positive electrode active material is more preferably a lithium composite oxide containing Ni (in other words, a Ni-containing lithium composite oxide). In the Ni-containing lithium composite oxide, the content of Ni is preferably in the range of 70 to 100 mol% with respect to the total number of moles of metals other than Li. In addition, in the lithium transition metal composite oxide, a part of Ni, Co, and Mn can be substituted with Al, Ti, Zr, P, B, Si, Nb, C, or the like. In addition, the positive electrode active material can also be a structure in which the surface of the particles of the lithium transition metal composite oxide is covered with a compound containing Al, Ti, Zr, W, P, B, Si, Nb, C, or the like. As the substitution amount and the addition amount, the total is about 0.1 to 7 mass%. On the other hand, as the positive electrode active material, a lithium transition metal phosphoric compound such as lithium iron phosphate can also be used. The positive electrode active material layer can also contain an electrically conductive material, a binder, or the like. In addition, as the electrically conductive material, a carbon material such as carbon black, a carbon nanotube, or the like is preferable. In addition, as the binder, a resin binder such as polyvinylidene fluoride is preferable.

[0083] Typically, the negative electrode 24 has a negative electrode current collector and a negative electrode active material layer fixed to at least one surface of the negative electrode current collector. The negative electrode current collector is composed of, for example, a conductive metal such as copper, copper alloy, nickel, stainless steel, or the like. Here, the negative electrode current collector is a metal foil, specifically, a copper foil. In the present embodiment, in the negative electrode 24, a portion where the negative electrode active material layer is not formed so that the negative electrode current collector is exposed is formed, and the exposed portion constitutes a current collector tab. However, the method of constituting the current collector tab is not limited thereto.

[0084] The negative electrode active material layer contains a negative electrode active material capable of reversibly adsorbing and releasing a charge carrier. As examples of the negative electrode active material, carbon-based negative electrode active materials such as graphite, hard carbon, and soft carbon; Si-based negative electrode active materials such as Si and silicon oxide; silicon-carbon composite negative electrode active materials; Sn-based negative electrode active materials such as Sn; and the like can be given. The negative electrode active material layer can also contain a conductive material, an adhesion-improving material, a binder, and the like. As the binder, it is preferable to include styrene-butadiene rubber or carboxymethyl cellulose, or the like.

[0085] The separator 25 is a member that insulates the positive electrode active material layer and the negative electrode active material layer. As the separator 25, for example, a porous resin sheet composed of a polyolefin resin such as polyethylene (PE) or polypropylene (PP) is suitable. The porous resin sheet can be either a single-layer structure or a multi-layer structure (for example, a three-layer structure of PP / PE / PP).

[0086] It is preferable that an adhesive layer be provided on the surface of the separator 25. The adhesive layer contains, for example, an adhesive resin such as an acrylic resin or polyvinylidene fluoride. In the case where the separator 25 has the adhesive layer, it is easy to suppress the lamination misalignment of the separator 25 and the electrodes. The adhesive layer can be provided on the entire surface of the separator 25 or can be pattern-applied. The adhesive layer is adhered, for example, by pressure or heat.

[0087] A heat resistance layer (HRL) containing ceramic particles can also be provided on the surface of the separator 25. As the material of the ceramic particles, for example, alumina, boehmite, aluminum hydroxide, titanium dioxide, or the like can be given. The heat resistance layer preferably further contains a resin binder. The resin binder can be an adhesive resin such as an acrylic resin or polyvinylidene fluoride. By appropriately adding the resin binder to the heat resistance layer, the heat resistance layer can also function as an adhesive layer.

[0088] In one advantageous embodiment of the separator 25, the separator 25 has a base material composed of a polyolefin microporous film and a heat resistance layer and an adhesive layer on the surface of the base material on the positive electrode 23 side. Specifically, the heat resistance layer is laminated on the base material, and the adhesive layer is laminated on the heat resistance layer. On the other hand, on the surface of the base material on the negative electrode 24 side, there is no laminated layer. Thus, the base material directly abuts against the negative electrode 24.

[0089] As another embodiment of the separator 25, the separator 25 has: a base material of a porous resin sheet; and an adhesive layer on both surfaces of the base material. As still another embodiment of the separator 25, the separator 25 has: a base material of a porous resin sheet; an adhesive layer on one surface of the base material; and a heat-resistant layer on the other surface of the base material. In this embodiment, the heat-resistant layer can have the function of the adhesive layer. As another embodiment of the separator 25, the separator 25 has: a base material of a porous resin sheet; an adhesive layer on one surface of the base material; and a heat-resistant layer on the other surface of the base material, and further has an adhesive layer on the heat-resistant layer.

[0090] <electrolyte>

[0091] The electrolyte is housed in the inside of the battery case 10 together with the electrode body 20. The electrolyte can be the same as that of a general secondary battery, and is not particularly limited. The electrolyte is typically a non-aqueous liquid electrolyte (i.e., a non-aqueous electrolyte) containing a non-aqueous solvent and a supporting salt. The non-aqueous solvent includes, for example, ethylene carbonate (EC), methyl ethylene carbonate (EMC), dimethyl carbonate (DMC), and the like. The non-aqueous solvent is preferably a mixture of EC, EMC, and DMC in a total ratio of 100% by volume in a range of 1 to 99% by volume, respectively. The non-aqueous solvent can also contain a carboxylic acid ester such as methyl acetate. The supporting salt is also referred to as an electrolyte salt, and is, for example, a lithium salt containing fluorine. As examples of the lithium salt containing fluorine, LiPF6, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI), and the like can be listed. The supporting salt preferably contains LiPF6. The concentration of the supporting salt is not particularly limited, but is preferably 0.6 to 1.8 mol / L, and more preferably 0.7 mol / L to 1.3 mol / L. The electrolyte can contain an additive, for example, a coating film forming agent such as vinyl carbonate (VC), an oxalate complex, and the like; a gas generating agent; a tackifier; and the like.

[0092] The secondary battery 100 can suppress electrode damage caused by an impact, a vibration, or the like at the time of manufacturing at a high level. The secondary battery 100 can be used for various uses. As suitable uses, vehicle-mounted uses, specifically, a driving power source mounted on a vehicle such as a battery electric vehicle (BEV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like can be listed. In addition, the secondary battery 100 can be used as a storage battery of a small-sized power storage device or the like. The secondary battery 100 can be used in a form in which a plurality of battery modules connected in series and / or in parallel.

[0093] The above describes specific examples of the present disclosure in detail, but these are merely examples and do not limit the claims. The technology recited in the claims includes various modifications and changes to the above-described specific examples.

[0094] That is, the secondary battery of the present disclosure is the following items [1] to

[10] .

[0095] [1] A secondary battery comprising: a laminated electrode body including a plurality of first electrode plates, a plurality of second electrode plates having a polarity different from the first electrode plates, and a belt-shaped separator; and a battery case that houses the laminated electrode body, wherein

[0096] the separator includes:

[0097] a plurality of folded portions folded in a plurality of folds in a manner disposed between the first electrode plates and the second electrode plates, and

[0098] a winding portion wound around an outer periphery of a portion of the laminated electrode body in which the first electrode plates, the second electrode plates, and the plurality of folded portions of the separator are laminated,

[0099] the separator includes a start end portion that is an end portion on one side in a longitudinal direction of the separator and an end end portion that is an end portion on the other side,

[0100] the end end portion is located at an end of winding of the winding portion,

[0101] the plurality of folded portions include:

[0102] a first folded portion disposed on one side in a direction perpendicular to a laminating direction of the first electrode plates and the second electrode plates, and

[0103] a second folded portion disposed on the other side in the direction perpendicular to the laminating direction of the first electrode plates and the second electrode plates,

[0104] the separator has an extension portion located at a position closer to the start end portion than the plurality of folded portions and disposed between the second folded portion and the winding portion,

[0105] in the laminating direction of the plurality of first electrode plates and the plurality of second electrode plates, outer surfaces of electrode plates on one side of the outermost surface are covered by the separator, and outer surfaces of electrode plates on the other side of the outermost surface are also covered by the separator.

[0106] [2] The secondary battery according to item [1], wherein

[0107] the secondary battery further comprises an insulating sheet,

[0108] the separator overlapping portion is provided outside the first folded portion and overlaps the winding portion by two or more layers of the separator,

[0109] the insulating sheet is disposed on an outer surface side of the separator overlapping portion.

[0110] [3] The secondary battery according to any one of items [1] to [2], wherein

[0111] The stacked electrode body has a first electrode tab electrically connected to the first electrode plate at one end portion, and a second electrode tab electrically connected to the second electrode plate at the other end portion,

[0112] The battery case includes a case main body having a first opening at one end portion and a second opening at the other end portion, a first sealing plate sealing the first opening, and a second sealing plate sealing the second opening,

[0113] The first electrode terminal electrically connected to the first electrode plate is provided at the first sealing plate, and the second electrode terminal electrically connected to the second electrode plate is provided at the second sealing plate.

[0114] [4] The secondary battery according to item [3], wherein

[0115] In a cross section parallel to the first opening of the case main body, an inner dimension Dl of the case main body in a direction in which the first electrode plate extends and a dimension Wl of the first electrode plate along the inner dimension Dl satisfy Wl / Dl > 0.9.

[0116] [5] The secondary battery according to any one of items [2] to [4], wherein

[0117] The insulating sheet has an insulating sheet overlapping portion in which two or more insulating sheets overlap,

[0118] The insulating sheet overlapping portion is disposed outside the separator overlapping portion.

[0119] [6] The secondary battery according to item [5], wherein

[0120] The battery case has a gas discharge valve on a surface facing the separator overlapping portion, the gas discharge valve rupturing when a pressure in the battery case reaches a predetermined value or more, and discharging gas in the battery case to the outside of the battery case.

[0121] [7] The secondary battery according to any one of items [1] to [6], wherein

[0122] A first electrode plate located at an outermost surface in one direction of the stacked direction of the first electrode plate and the second electrode plate, that is, an outermost first electrode plate in one direction is disposed between the multiple folding portion and the winding portion.

[0123] [8] The secondary battery according to any one of items [1] to [7], wherein

[0124] The above-mentioned first electrode plate has a first electrode tab,

[0125] In a direction in which the above-mentioned first bent portion and the above-mentioned second bent portion are connected, the above-mentioned first electrode tab is deviated from the center of the above-mentioned first electrode plate in a direction away from the above-mentioned diaphragm overlapping portion.

[0126] [9] The secondary battery according to any one of items [1] to [8], wherein

[0127] A plurality of the above-mentioned electrode bodies are arranged in the above-mentioned battery case,

[0128] On the outermost surface of the above-mentioned electrode body, a winding termination tape is attached to the terminal portion of the above-mentioned diaphragm,

[0129] At least one of the above-mentioned winding termination tapes is arranged between a plurality of the above-mentioned electrode bodies.

[0130]

[10] The secondary battery according to any one of items [1] to [9], wherein

[0131] The above-mentioned first electrode plate is a negative electrode plate, and the above-mentioned second electrode plate is a positive electrode plate,

[0132] The above-mentioned diaphragm has a base material composed of a polyolefin microporous film, a heat-resistant layer on the surface of the above-mentioned base material on the side of the above-mentioned positive electrode plate, and an adhesive layer,

[0133] The above-mentioned base material directly abuts against the above-mentioned negative electrode plate.

Claims

1. A secondary battery comprising: a laminated electrode assembly comprising a plurality of first electrode plates, a plurality of second electrode plates having polarities different from those of the first electrode plates, and a strip-shaped separator; and a battery case housing the laminated electrode assembly, wherein: The above-mentioned diaphragm includes: a multi-fold portion that is bent into a multi-fold shape so as to be disposed between the first electrode plate and the second electrode plate; and a winding portion wound around the outer periphery of the portion of the multi-fold portion where the first electrode plate, the second electrode plate, and the separator are stacked; The diaphragm includes a starting end portion as one end portion in the longitudinal direction of the diaphragm and a terminal end portion as the other end portion. The terminal portion is located at the winding end of the winding portion. The multi-fold portion includes: a first bent portion disposed on one side in a direction perpendicular to a stacking direction of the first electrode plate and the second electrode plate; and a second bent portion disposed on the other side in a direction perpendicular to the stacking direction of the first electrode plate and the second electrode plate, The diaphragm has an extending portion located closer to the starting end portion than the multi-fold portion and disposed between the second bent portion and the winding portion. In the stacking direction of the plurality of the first electrode plates and the plurality of the second electrode plates, among the plurality of the first electrode plates and the plurality of the second electrode plates, the outer surface of the electrode plate on the outermost surface side is covered by the diaphragm, and the outer surface of the electrode plate on the other outermost surface side is also covered by the diaphragm.

2. The secondary battery according to claim 1, wherein The secondary battery further comprises an insulating sheet. A diaphragm overlapping portion having two or more layers of the winding portion is provided on the outer side of the first bent portion. The insulating sheet is arranged on the outer surface side of the diaphragm overlapping portion.

3. The secondary battery according to claim 1, wherein The stacked electrode body has a first electrode tab at one end electrically connected to the first electrode plate, and a second electrode tab at the other end electrically connected to the second electrode plate. The battery case includes: a case body having a first opening at one end and a second opening at the other end; a first sealing plate for sealing the first opening; and a second sealing plate for sealing the second opening. The first sealing plate is provided with a first electrode terminal electrically connected to the first electrode plate, and the second sealing plate is provided with a second electrode terminal electrically connected to the second electrode plate.

4. The secondary battery according to claim 3, wherein In a cross section parallel to the first opening of the case body, an inner dimension D1 of the case body in the direction in which the first electrode plate extends and a dimension W1 of the first electrode plate along the inner dimension D1 satisfy W1 / D1>0.

9.

5. The secondary battery according to claim 2, wherein The insulating sheet has an insulating sheet overlapping portion in which two or more layers are overlapped. The insulating sheet overlapping portion is arranged outside the diaphragm overlapping portion.

6. The secondary battery according to claim 5, wherein The battery case includes a gas discharge valve on a surface facing the separator overlapping portion. The gas discharge valve ruptures when the pressure in the battery case exceeds a predetermined value to discharge the gas in the battery case to the outside of the battery case.

7. The secondary battery according to claim 1, wherein The first electrode plate located on one outermost surface in the stacking direction of the first electrode plate and the second electrode plate, that is, one outermost first electrode plate, is arranged between the multi-fold portion and the winding portion.

8. The secondary battery according to claim 1, wherein The first electrode plate has a first electrode tab. In a direction connecting the first bent portion and the second bent portion, the first electrode tab is offset from the center of the first electrode plate in a direction away from the separator overlapping portion.

9. The secondary battery according to claim 1, wherein A plurality of the electrode bodies are arranged in the battery case. On the outermost surface of the electrode body, a winding end tape is attached to the terminal end of the separator. At least one winding termination tape is disposed between the plurality of electrode bodies.

10. The secondary battery according to claim 1, wherein The first electrode plate is a negative electrode plate, and the second electrode plate is a positive electrode plate. The separator comprises a substrate composed of a polyolefin microporous film, a heat-resistant layer and an adhesive layer located on the surface of the substrate facing the positive electrode plate. The substrate is in direct contact with the negative electrode plate.

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