Nonaqueous electrolyte secondary battery

Abstract

The invention relates to a nonaqueous electrolyte secondary battery. Provided is a non-aqueous electrolyte secondary battery in which a battery case is less likely to crack in an unexpected portion. According to the present invention, provided is a nonaqueous electrolyte secondary battery comprising a laminated electrode body and a battery case. The battery case has a lower surface on which a gas discharge valve is provided. The laminated electrode body has a pair of flat surfaces, a lower end surface, and an upper end surface, and a tape is attached to the laminated electrode body so as to straddle the pair of flat surfaces. The lower end surface and the upper end surface of the laminated electrode body are asymmetrically covered by the tape.

Description

Technical Field

[0001] The present invention relates to a non-aqueous electrolyte secondary battery. Background Art

[0002] Currently, nonaqueous electrolyte secondary batteries are known that include a stacked electrode assembly, a nonaqueous electrolyte, and a battery case that houses the stacked electrode assembly and the nonaqueous electrolyte. Prior art documents related to such nonaqueous electrolyte secondary batteries include Japanese Patent Application Publication No. 2008-91099, Japanese Patent Application Publication No. 2016-194979, and International Publication No. 2017 / 033420. For example, Japanese Patent Application Publication No. 2008-91099 describes attaching a tape to the stacked electrode assembly to prevent stacking deviation.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2008-91099

[0006] Patent Document 2: International Publication No. 2017 / 033420

[0007] Patent Document 3: Japanese Patent Application Laid-Open No. 2016-194979 Summary of the Invention

[0008] According to the inventors' research, when the temperature rises due to overcharging or other factors, the non-aqueous electrolyte in the battery may decompose, generating gas. Consequently, if the pressure within the battery exceeds a specified value, the battery case may crack in unexpected locations, causing the battery contents (e.g., fragments of the active material layer) to be discharged from the cracked area and scattered to the surrounding area.

[0009] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a non-aqueous electrolyte secondary battery in which the battery case is less likely to crack at unexpected locations.

[0010] According to the present invention, a non-aqueous electrolyte secondary battery is provided, comprising: a stacked electrode body having a plurality of positive electrodes and a plurality of negative electrodes; a non-aqueous electrolyte; and a battery case housing the stacked electrode body and the non-aqueous electrolyte. The battery case comprises at least a lower surface; a pair of side surfaces extending from a pair of edges of the lower surface and opposing each other; and an upper surface opposing the lower surface, wherein a gas discharge valve is provided on the lower surface. The stacked electrode body comprises: a pair of flat surfaces opposing the pair of side surfaces of the battery case; a lower end surface opposing the lower surface of the battery case; and an upper end surface opposing the upper surface of the battery case, wherein the lower end surface and the upper end surface are end surfaces where the stacked structure of the positive electrodes and the negative electrodes is exposed. At least one tape material is attached to the stacked electrode body so as to span the pair of flat surfaces, and the lower end surface and the upper end surface of the stacked electrode body are asymmetrically covered by the tape material so that gas flows toward the gas discharge valve.

[0011] According to the present invention, the gas generated in the battery can be easily and stably discharged to the outside through the gas discharge valve provided on the lower surface of the battery case, thereby preventing the battery case from cracking in unexpected (unpredictable) places. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a perspective view schematically showing a non-aqueous electrolyte secondary battery according to one embodiment.

[0013] Figure 2 To make Figure 1 A perspective view of a non-aqueous electrolyte secondary battery turned upside down.

[0014] Figure 3 To follow Figure 1 Schematic longitudinal cross-sectional view along line III-III.

[0015] Figure 4 (A) to (C) are schematic plan views showing modified examples of the gas discharge valve.

[0016] Figure 5 To illustrate Figure 3 A three-dimensional diagram of a stacked electrode body.

[0017] Figure 6 To illustrate Figure 5 A three-dimensional diagram of the gas flow in the stacked electrode body.

[0018] Figure 7 (A) and (B) are the results of Comparative Examples 1 and 2. Figure 6 Picture.

[0019] Figure 8(A)-(C) are the corresponding values ​​of Comparative Examples 3-1 to 3-3. Figure 6 Picture.

[0020] Figure 9 (A) and (B) are examples 2-1 and 2-2 corresponding to Figure 6 Picture.

[0021] Figure 10 (A) and (B) are examples 3-1 and 3-2 corresponding to Figure 6 Picture.

[0022] Figure 11 (A) and (B) are examples 4-1 and 4-2 corresponding to Figure 6 Picture.

[0023] Figure 12 For example 6, the corresponding Figure 6 Picture.

[0024] Figure 13 (A) and (B) are examples 7-1 and 7-2 corresponding to Figure 6 Picture.

[0025] Figure 14 (A) and (B) are examples 8-1 and 8-2 corresponding to Figure 6 Picture.

[0026] Figure 15 (A) and (B) are examples 9, 10, and 11 corresponding to Figure 6 Picture.

[0027] Figure 16 (A) and (B) are examples 12 and 13 corresponding to Figure 6 Picture.

[0028] Description of Reference Numerals

[0029] 10 Battery housing

[0030] 12 Shell body

[0031] 12a Lower surface

[0032] 12b Long Side

[0033] 13, 113, 213, 313 gas discharge valve

[0034] 14 Sealing plate

[0035] 20 stacked electrode body

[0036] E1 lower end face

[0037] E2 upper end face

[0038] F1 First flat surface

[0039] P1 Part opposite to the gas discharge valve

[0040] t Strip

[0041] 100 battery (non-aqueous electrolyte secondary battery) DETAILED DESCRIPTION

[0042] The following describes in detail several embodiments of the technology disclosed herein with reference to the accompanying drawings. Furthermore, matters other than those specifically mentioned in this specification and matters required for the implementation of the technology disclosed herein (such as the general structure and manufacturing process of non-aqueous electrolyte secondary batteries that are not characteristics of the technology disclosed herein) can be understood as design matters based on prior art in this field by those skilled in the art. The technology disclosed herein can be implemented based on the contents disclosed in this specification and technical common sense in this field. In addition, in the following drawings, the same figure marks are marked and described for components and parts that play the same role.

[0043] In this specification, "non-aqueous electrolyte secondary battery" refers to any energy storage device that allows repeated charge and discharge by transferring charge carriers between a positive electrode and a negative electrode via a non-aqueous electrolyte. In this specification, the expression "A to B" indicating a range includes the meaning of "greater than A and less than B," as well as "greater than A" and "smaller than B."

[0044] Figure 1 FIG1 is a perspective view of a nonaqueous electrolyte secondary battery (hereinafter sometimes simply referred to as a “battery”) 100 according to one embodiment. Figure 2 To make Figure 1 FIG. 1 is a perspective view of the battery 100 that is turned upside down. Figure 3 for Figure 1 A schematic longitudinal cross-sectional view of battery 100 taken along line III-III illustrates its internal structure. In the following description, reference numerals L, R, F, Rr, U, and D represent left, right, front, rear, top, and bottom, respectively. Reference numerals X, Y, and Z represent the thickness direction of battery 100, the width direction perpendicular to the thickness direction, and the vertical direction perpendicular to the thickness and width directions, respectively. The vertical direction Z is typically the vertical direction.

[0045] Battery 100 Figure 1 The battery 100 is mounted on a vehicle, etc., in the direction shown. Here, the battery 100 is a square battery having a square shape (specifically, a rectangular parallelepiped shape) composed of hexahedrons. Figure 3As shown, battery 100 includes a battery case 10, a laminated electrode assembly 20, a non-aqueous electrolyte (not shown), a positive electrode terminal 30, and a negative electrode terminal 40. The non-aqueous electrolyte is an example of a non-aqueous electrolyte. Battery 100 is a non-aqueous electrolyte secondary battery, specifically a lithium-ion secondary battery.

[0046] The battery case 10 is an outer shell that contains the stacked electrode body 20 and the non-aqueous electrolyte. Figure 1 、 Figure 2 As shown, the battery case 10 has a flat, bottomed rectangular parallelepiped (square) shape. The material of the battery case 10 can be the same as that used in the past and is not particularly limited. The battery case 10 is preferably made of metal, and more preferably, is made of aluminum, an aluminum alloy, iron, or an iron alloy.

[0047] like Figure 3 As shown, the battery case 10 includes a case body 12 and two sealing plates 14. The case body 12 has a pair of openings 12h at both ends in the width direction Y. The two sealing plates 14 block the pair of openings 12h of the case body 12. The battery case 10 is integrated by joining the sealing plates 14 to the periphery of the pair of openings 12h of the case body 12 (for example, by welding). The battery case 10 is hermetically sealed (sealed).

[0048] The shell body 12 is in the shape of a square tube. Figure 1 As shown, it includes: a lower surface 12a having a generally rectangular shape with long sides and short sides, a pair of long side surfaces 12b extending from a pair of opposite long sides (edges) of the lower surface 12a and facing each other, and an upper surface 12c opposite the lower surface 12a. The area of ​​the long side surfaces 12b is larger than that of the lower surface 12a and the upper surface 12c. The upper surface 12c is also generally rectangular like the lower surface 12a. The upper surface 12c connects the upper end portions of the pair of long side surfaces 12b. The shell body 12 is formed, for example, by bending a metal plate, forming it into a cylindrical shape, and joining the seams (for example, by welding). Here, a welding joint 12d is provided on the upper surface 12c.

[0049] like Figure 2As shown, a gas discharge valve 13 is provided on the lower surface 12a. The gas discharge valve 13 is configured to break when the pressure in the battery case 10 becomes above a specified value, thereby discharging the gas in the battery case 10 to the outside. The lower surface 12a is a surface that contacts the frame (typically made of metal) of the module or battery pack and is easy to dissipate heat. Therefore, by providing the gas discharge valve 13 on the lower surface 12a, the gas generated in the battery case 10 contacts the lower surface 12a and is easily cooled. As a result, the temperature rise of the gas and the pressure rise in the battery 100 can be suppressed, and the battery case 10 can be suppressed from cracking in unexpected places. In addition, since the gas is cooled, the momentum of the gas is weakened, and it is difficult for the contents of the battery 100 to fly over a large area.

[0050] Furthermore, in this embodiment, the number of the gas discharge valve 13 is one, but it may be two or more. In addition, the area of ​​the gas discharge valve 13 is arbitrary. Figure 2 As shown, in this embodiment, the gas discharge valve 13 is a cross-shaped cutout. However, the shape of the gas discharge valve 13 is not particularly limited. In another embodiment, the gas discharge valve 13 may be a linear cutout (only vertical or horizontal lines), an X-shaped cutout, or an H-shaped cutout. For example, the gas discharge valve 13 may be a groove in the shape of a circle, an ellipse, a quadrilateral, a diamond, a triangle, a star, or a combination thereof. In addition, the dimensions (length, width, depth) of the cutout or groove are arbitrary and can be appropriately determined, for example, taking into account the pressure resistance of the battery case 10.

[0051] like Figure 2 As shown, the gas discharge valve 13 is preferably set at a position that coincides with the center of gravity G of the lower surface 12a of the battery case 10. In other words, the gas discharge valve 13 is preferably configured in such a way that the center of gravity G of the lower surface (the surface having the gas discharge valve 13) 12a exists in the gas discharge valve 13 (inside the gas discharge valve 13). As a result, fluctuations in the amount of gas are less likely to occur in the battery case 10, and the deviation in the gas pressure becomes smaller when the gas is discharged from the gas discharge valve 13. Therefore, the effect of the technology disclosed herein can be exerted at a higher level. Furthermore, as Figure 2 As shown, when the lower surface 12a is flat and rectangular, the intersection of two diagonal lines shown by imaginary lines is the center of gravity G.

[0052] The gas discharge valve 13 has a center C. Figure 2 In the embodiment, the center C of the gas discharge valve 13 coincides with the center of gravity G of the lower surface 12a of the battery case 10. However, in another embodiment, the center C of the gas discharge valve 13 may not coincide with the center of gravity G of the lower surface 12a. For example, the center C of the gas discharge valve 13 may be located at a position offset to one side in the width direction Y relative to the center of gravity G of the lower surface 12a.

[0053] exist Figure 4(A)-(C) show several variations of the gas discharge valve. Figure 4 In (A) to (C), the gas exhaust valve 13 is provided at a position that coincides with the center of gravity G of the lower surface 12a of the battery case 10. Specifically, Figure 4 The gas discharge valve 113 shown in (A) has a cross-shaped cutout inside an elliptical groove. Figure 4 In (A), the center C of the gas discharge valve 113 coincides with the center of gravity G of the lower surface 12a. Figure 4 The gas discharge valve 213 shown in (B) has an X-shaped cutout inside an elliptical groove. Figure 4 In (B), the center C of the gas exhaust valve 213 is located at a position offset to the left in the width direction Y from the center of gravity G of the lower surface 12 a . Figure 4 The gas discharge valve 313 shown in (C) is in the shape of a circular groove. Figure 4 In (C), the center C of the gas discharge valve 313 coincides with the center of gravity G of the lower surface 12a.

[0054] The sealing plate 14 is a plate-shaped member that seals the opening 12h. The sealing plate 14 is roughly rectangular when viewed from above. The area of ​​the sealing plate 14 is smaller than the long side 12b. A liquid injection hole 15 is provided in the sealing plate 14. The liquid injection hole 15 is used to inject non-aqueous electrolyte into the interior of the battery case 10 after the sealing plate 14 is mounted on the case body 12. The liquid injection hole 15 is sealed with a sealing member 16 after the non-aqueous electrolyte is injected. Furthermore, in this embodiment, the liquid injection hole 15 is provided in the sealing plate 14, but in another embodiment, the liquid injection hole 15 may be provided in the case body 12.

[0055] The positive terminal 30 and the negative terminal 40 are fixed to the surfaces (specifically, a pair of sealing plates 14) facing each other with respect to the battery case 10. Specifically, the positive terminal 30 is mounted on one side ( Figure 1 、 Figure 2 The negative terminal 40 is mounted on the other side ( Figure 1 、 Figure 2 In this embodiment, the positive electrode terminal 30 and the negative electrode terminal 40 are respectively provided on a pair of sealing plates 14. However, in another embodiment, the positive electrode terminal 30 and the negative electrode terminal 40 may be provided on the same sealing plate 14 or on the case body 12.

[0056] The positive terminal 30 and the negative terminal 40 are each exposed on the outer surface of the sealing plate 14. Here, the positive terminal 30 and the negative terminal 40 are arranged on an axis that passes through the center of the sealing plate 14 along the width direction Y. However, in another embodiment, the axis may be offset from the center of the sealing plate 14, for example, in the thickness direction X. In addition, the positive terminal 30 and the negative terminal 40 may not be arranged on the axis. For example, one of the positive terminal 30 and the negative terminal 40 may be offset to one side in the thickness direction X, and the other may be offset to the other side in the thickness direction X.

[0057] like Figure 3 As shown, the positive electrode terminal 30 is electrically connected to the positive electrode tab 23 of the stacked electrode body 20 via the positive electrode current collecting portion 32 inside the battery case 10. The positive electrode terminal 30 is preferably made of metal, more preferably, aluminum or an aluminum alloy. The negative electrode terminal 40 is electrically connected to the negative electrode tab 24 of the stacked electrode body 20 via the negative electrode current collecting portion 42 inside the battery case 10. The negative electrode terminal 40 is preferably made of metal, more preferably, copper or a copper alloy.

[0058] like Figure 3 As shown, the stacked electrode body 20 is housed inside the battery case 10 . Figure 5 FIG is a perspective view of the stacked electrode body 20. Figure 5 As shown, the stacked electrode body 20 is composed of multiple square positive electrodes and multiple square negative electrodes stacked in the thickness direction X through a separator in an insulated state. The stacked electrode body 20 housed inside the battery case 10 can be only one. For example, when the number of stacked electrode bodies 20 is less than one, there can be two, three, or other stacked electrode bodies 20. The thickness direction X is the stacking direction of the multiple positive electrodes and the multiple negative electrodes. The various components (positive electrode, negative electrode, separator, etc.) that constitute the stacked electrode body 20 can be the same as those of a general non-aqueous electrolyte secondary battery and are not particularly limited.

[0059] The positive electrode typically has a positive electrode collector and a positive electrode active material layer fixed on at least one surface of the positive electrode collector. The positive electrode collector is in a strip shape. The positive electrode collector is made of, for example, a conductive metal such as aluminum, an aluminum alloy, nickel, or stainless steel. The positive electrode collector is a metal foil, specifically aluminum foil. A positive electrode tab 23 is provided on the positive electrode. The positive electrode tab 23 is a part of the positive electrode collector. The positive electrode tab 23 is convex and extends from the stacked electrode body 20 to one side in the width direction Y ( Figure 3 The positive electrode tab 23 is electrically connected to the positive electrode terminal 30 via the positive electrode current collecting portion 32.

[0060] The positive electrode active material layer is arranged in a strip shape along the longitudinal direction of the strip-shaped positive electrode current collector. The positive electrode active material layer contains a positive electrode active material capable of reversibly occluding and releasing charge carriers. The positive electrode active material is preferably an oxide containing at least one of nickel, cobalt, and manganese. Examples include lithium transition metal composite oxides such as lithium cobaltate, lithium manganeseate, lithium nickelate, lithium nickel-manganese composite oxide, and lithium nickel-cobalt composite oxide. For example, the positive electrode active material is a composite oxide containing nickel and lithium, preferably a lithium nickel composite oxide in which the nickel content of the composite oxide is 70 to 100 mol% relative to the total molar number of constituent elements in the composite oxide excluding lithium and oxygen. Positive electrode active materials also include products in which a portion of the nickel, cobalt, or manganese content is replaced with aluminum, titanium, zirconium, phosphorus, boron, silicon, niobium, or carbon, or products in which the particle surface is coated with compounds containing aluminum, titanium, zirconium, vanadium, phosphorus, boron, silicon, niobium, or carbon. The total amount of replacement and addition is approximately 0.1 to 7%.

[0061] The negative electrode typically has a negative electrode current collector and a negative electrode active material layer fixed on at least one surface of the negative electrode current collector. The negative electrode current collector is in a strip shape. The negative electrode current collector is made of, for example, a conductive metal such as copper, a copper alloy, nickel, or stainless steel. The negative electrode current collector is a metal foil, specifically a copper foil. A negative electrode sheet 24 is provided at the negative electrode. The negative electrode sheet 24 is a part of the negative electrode current collector. The negative electrode sheet 24 is convex and extends from the stacked electrode body 20 toward the other side in the width direction Y ( Figure 3 The negative electrode tab 24 is electrically connected to the negative electrode terminal 40 via the negative electrode current collecting portion 42.

[0062] The negative electrode active material layer is arranged in a strip shape along the longitudinal direction of the strip-shaped negative electrode current collector. The negative electrode active material layer contains a negative electrode active material capable of reversibly occluding and releasing charge carriers. Examples of negative electrode active materials include carbon materials such as graphite and carbon, and metals capable of occluding lithium, such as Si, SiO, SiC, and Sn, and their compounds.

[0063] The separator (diaphragm) is a member that insulates the positive electrode active material layer from the negative electrode active material layer. Preferred separators include porous resin sheets made of polyolefin resins such as polyethylene (PE) and polypropylene (PP). A heat-resistant layer (HRL) containing an inorganic filler may be provided on the surface of the separator. Examples of inorganic fillers include alumina, boehmite, aluminum hydroxide, and titanium dioxide.

[0064] like Figure 5As shown, the overall shape of the stacked electrode body 20 is substantially a rectangular parallelepiped. The stacked electrode body 20 is arranged inside the battery case 10 in a direction (direction) perpendicular to the lower surface 12a of the case body 12 in the stacking direction (see also FIG. Figure 3 The stacked electrode body 20 has a surface (a first flat surface F1, Figure 5 the front side of the surface), and the other side surface (the second flat surface, Figure 5 The first flat surface F1 is aligned with the first long side surface 12b of the housing body 12 (see Figure 1 ) opposite to the second flat surface, the second flat surface is the surface opposite to the second long side surface 12b of the shell body 12.

[0065] The stacked electrode body 20 has a stacked structure of multiple positive and negative electrodes, with four end faces E1 to E4 exposed along the stacking direction (thickness direction X). Specifically, the stacked electrode body 20 has a lower end face E1 facing the lower surface 12a of the battery case 10 (specifically, the case body 12), an upper end face E2 facing the upper surface 12c of the battery case 10 (specifically, the case body 12), and a right end face E3 and a left end face E4 facing the pair of sealing plates 14, respectively. End faces E1 to E4 are located between the first flat surface F1 and the second flat surface in the stacking direction (thickness direction X). End faces E1 to E4 constitute the outer periphery of the stacked electrode body 20.

[0066] The lower end surface E1 and the upper end surface E2 extend along the XY plane of the battery case 10. The lower end surface E1 has a portion P1 that faces the gas discharge valve 13 provided on the lower surface 12a of the case body 12. The upper end surface E2 has a portion P2 located vertically above the gas discharge valve 13. The portion P2 overlaps with the portion P1 when viewed from above and is located on the side of the stacked electrode body 20 opposite the portion P1. The right end surface E3 and the left end surface E4 extend along the XZ plane of the battery case 10. The convex positive electrode tab 23 protrudes from the right end surface E3. The convex negative electrode tab 24 protrudes from the left end surface E4.

[0067] On the outer surface of the stacked electrode body 20, at least one strip t is pasted in a manner spanning the first flat surface F1 (the surface opposite to the first long side surface 12b of the shell body 12) and the second flat surface (the surface opposite to the second long side surface 12b of the shell body 12). The configuration of the strip t (such as the width, type, pasting position, and quantity of the strip t) is not particularly limited as long as it does not significantly impair the effect of the technology disclosed herein. The lower end surface E1 and the upper end surface E2 are preferably each covered at least in part by at least one strip t. In this way, stacking deviation is suppressed, and the stacking structure is easily and stably maintained. The right end surface E3 of the positive electrode sheet 23 and the left end surface E4 of the negative electrode sheet 24 are preferably not covered by the strip t. In this way, the precipitation of metallic lithium (dendrites) can be suppressed, and it is easy to exert high charge and discharge performance for a long time.

[0068] As the tape t, it can be the same as the tape used for this purpose in the past, and there is no particular limitation. The tape t preferably has high bonding strength, more preferably high heat resistance. The tape t is typically made of plastic films such as various engineering plastics (PET, PEN, PI, PPE, etc.), olefin films (PE, OPP, TPX, etc.), PMMA, TAC, and metal films coated with plastic on both sides or ends, and has a structure in which an adhesive layer is configured on one side. As a specific example of the tape t of plastic film, for example, PTFE film tape, acetate cloth tape, epoxy tape, glass cloth tape, vinyl plastic tape, polyimide tape, polyester tape, etc. can be listed. In addition, as the tape t of metal film, compared with the tape exposed by the metal part, for example, aluminum foil tape, copper foil tape, stainless steel foil tape, etc. coated by resin film are preferably used, and the metal part can be an alloy. The heat resistance of the metal film tape t is excellent, but it is also possible that the exposure of the metal part caused by the incision causes a short circuit. Therefore, when using a metal film tape t, it is preferable to further adhere a plastic film tape after applying the tape t so that the metal film portion is completely covered. The metal film tape t is preferably a metal tape with a metal portion (such as stainless steel foil) having a melting point of 1000°C or higher.

[0069] In several embodiments, the strip t is preferably porous. This can improve the permeability of the non-aqueous electrolyte to the stacked electrode body 20. It can even improve battery characteristics such as rapid charging and discharging. Therefore, the technical effects disclosed herein can be balanced with the battery characteristics. In particular, in the scheme where at least one of the lower end surface E1 and the upper end surface E2 is completely covered by the strip t, the strip t is preferably porous. Although not particularly limited, from the perspective of exerting the effects of the technology disclosed herein at a high level, the porosity of the strip t is preferably approximately less than 50%, for example, more preferably 20 to 40%. In one example, the porosity of the strip t is more preferably smaller than the porosity of the separator. Furthermore, the porosity (%) of the strip t can be calculated by the following formula: [1-(apparent density / true density)]×100. The above true density can be calculated based on the density and content ratio of the constituent components of the strip t. The above apparent density can be calculated from the weight and volume of the strip t.

[0070] exist Figure 5 In the embodiment, at least one strip t is affixed to the lower end surface E1 and the upper end surface E2. Specifically, a plurality of (specifically, two) strips t1 and t2 are affixed to the lower end surface E1. The strips t1 and t2 are affixed along the width direction Y with intervals therebetween. On the other hand, a strip t3 is affixed to the upper end surface E2. The plurality of strips t are asymmetrically affixed vertically. In this embodiment, the lower end surface E1 and the upper end surface E2 are asymmetrically covered with at least one strip t in such a manner that the gas flows toward the gas discharge valve 13 (preferably, in such a manner that the gas flow is induced toward the gas discharge valve 13).

[0071] Figure 6 The figure is a three-dimensional diagram schematically showing the flow of gas in the stacked electrode body 20. In addition, the following figures are not intended to be interpreted in a particularly limiting manner. Based on the results of computer simulation, arrows are used to represent the flow of gas generated in the stacked electrode body 20. The thickness of the arrow is proportional to the amount of gas. The thicker the arrow, the more gas there is. In addition, the length of the arrow is proportional to the speed of the gas. The longer the arrow, the faster the gas flows. Figure 6 As shown in FIG, according to this embodiment, while preventing stacking deviation, it is easy to guide the gas generated in the stacked electrode body 20 to the gas discharge valve 13. As a result, the generated gas is easily and stably discharged to the outside through the gas discharge valve 13. Therefore, it is possible to suppress the battery case 10 from cracking in unexpected places.

[0072] exist Figure 5In the embodiment, the length Wb of the strip t3 in the width direction Y pasted on the upper end surface E2 is longer than the length Wa of the strips t1 and t2 pasted on the lower end surface E1 (i.e., Wa<Wb). In some embodiments, the area An covered by the strip t3 in the upper end surface E2 is preferably larger than the area Am covered by the strips t1 and t2 in the lower end surface E1 (i.e., Am<An). As a result, it is easy to induce the gas generated in the stacked electrode body 20 to the gas discharge valve 13 provided on the lower surface 12a of the shell body 12. As a result, the generated gas can be easily and stably discharged to the outside from the gas discharge valve 13. In addition, it is possible to suppress the occurrence of cracks in any part of the battery shell 10 at a higher level.

[0073] exist Figure 5 In the embodiment, the portion P2 of the upper end surface E2 located vertically above the gas discharge valve 13 is covered with the tape t3. In some embodiments, the portion P2 of the upper end surface E2 located vertically above the gas discharge valve 13 is preferably covered with the tape t. As a result, the gas generated within the stacked electrode body 20 collides with the portion P2 of the tape t, easily generating a downward airflow. As a result, the generated gas is easily and stably discharged to the outside from the gas discharge valve 13. In addition, cracking of any part of the battery case 10 can be suppressed to a higher level.

[0074] exist Figure 5 In the embodiment, the tapes t1 and t2 of the lower end surface E1 are attached, leaving the portion P1 facing the gas discharge valve 13. That is, the portion P1 facing the gas discharge valve 13 is not covered by the tape t. In some embodiments, the portion P1 of the lower end surface E1 facing the gas discharge valve 13 is preferably not covered by the tape t. This facilitates the discharge of gas generated in the stacked electrode assembly 20 from the gas discharge valve 13 to the outside.

[0075] exist Figure 5 In the embodiment, the entire lower end surface E1, except for the portion P1 facing the gas release valve 13, is covered with tapes t1 and t2 (allowing for human and mechanical errors, etc.). The tape t3 on the upper end surface E2 is affixed along the width direction Y to a length substantially equal to that of the upper end surface E2. The entire upper end surface E2 (the entire upper end surface E2) is covered with tape t3 (allowing for human and mechanical errors, etc.). In some embodiments, the portion P1 of the lower end surface E1 facing the gas release valve 13 is not covered with tape t. Furthermore, when the length of the portion not facing the gas release valve 13 (excluding the portion P1 facing the gas release valve 13) in the width direction Y (along the long side 12b of the battery case 10) is set to 100%, preferably at least 10% of the length is covered with tape t. This facilitates the induction of gas generated within the stacked electrode assembly 20 into the gas release valve 13. Consequently, cracking of the battery case 10 at any location can be suppressed to a high degree.

[0076] The length of the entire non-opposing portion covered by the tape t is preferably 20% or more, further preferably 50% or more, and particularly preferably 80% or more. Furthermore, in this case, with respect to the upper end surface E2, the proportion of the width direction Y covered by the tape t is preferably greater than the portion of the lower end surface E1 that does not oppose the gas discharge valve 13. More preferably, the tape t covers 30% or more (particularly 40% or more) of the total length in the width direction Y.

[0077] In some embodiments, the entire lower end surface E1, except for the portion P1 facing the gas discharge valve 13, is preferably covered with at least one tape t. Furthermore, the entire upper end surface E2 is preferably covered with at least one tape t. This facilitates directing gas generated within the stacked electrode assembly 20, particularly toward the gas discharge valve 13. Consequently, cracking of any portion of the battery case 10 can be suppressed to a particularly high degree.

[0078] exist Figure 5 In the figure, the strip t3 affixed to the upper end surface E2 extends to the side of the first flat surface F1 (the surface opposite the first long side 12b of the housing body 12) (towards the bottom). Although not shown in the figure, the strip t3 similarly extends to the side of the second flat surface (the surface opposite the second long side 12b of the housing body 12). Furthermore, the strips t1 and t2 affixed to the lower end surface E1 extend to the side of the first flat surface F1 (the surface opposite the first long side 12b of the housing body 12) (towards the top). Although not shown in the figure, the strips t1 and t2 similarly extend to the side of the second flat surface (the surface opposite the second long side 12b of the housing body 12). The length Lt (in the vertical direction Z) of the strip t3 affixed to the upper end surface E2 extending along the first flat surface F1 is the same as the length Ls (in the vertical direction Z) of the strips t1 and t2 affixed to the lower end surface E1 extending along the first flat surface F1 (allowing for human error and mechanical error, etc.).

[0079] However, in some embodiments, the length Lt of the tape t attached to the upper end surface E2 extending along the first flat surface F1 is preferably longer than the length Ls of the tape t attached to the lower end surface E1 extending along the first flat surface F1 (i.e., Ls < Lt). By extending the length of the tape t on the upper end surface E2 side, that is, attaching the tape t to the portion of the first flat surface F1 away from the gas discharge valve 13, this portion becomes thicker. As a result, the reaction force of the portion to which the tape t is attached is increased, and this portion can withstand high pressure. As a result, the gas generated in the stacked electrode body 20 becomes difficult to escape (escape) from above and is easily guided toward the gas discharge valve 13 below. Therefore, cracking of the battery case 10 at any location can be suppressed to a higher level. Furthermore, when multiple tapes t are attached to the upper end surface E2 and / or the lower end surface E1, it is preferred that the arithmetic average of the lengths of the multiple tapes t satisfy the above description.

[0080] In addition, Figure 5 In the embodiment, the tapes t1 and t2 of the lower end surface E1 are attached, leaving the portion P1 facing the gas discharge valve 13. However, a portion or all of the portion P1 facing the gas discharge valve 13 may be covered by the tape t. In this case, in some embodiments, the portion P1 of the lower end surface E1 facing the gas discharge valve 13 is preferably covered by the tape t, except for the portion facing the center of the gas discharge valve 13. Furthermore, the portion of the upper end surface E2 located vertically above the center of the gas discharge valve 13 is preferably covered by the tape t. In this way, by partially covering the portion P1 of the lower end surface E1 facing the gas discharge valve 13 with the tape t, the gas is concentrated in the portion not covered by the tape t (the portion facing the center of the gas discharge valve 13), increasing the gas momentum and making it easier to open the gas discharge valve 13 early. Therefore, cracking in any portion of the battery case 10 can be suppressed to a higher level. It should be noted that in this specification, the so-called "center part of the gas exhaust valve 13" refers to the center C and its peripheral part (when the overall area of ​​the gas exhaust valve 13 is set to 100, the area range from the center C to approximately 70%, preferably within 30%, and more preferably within 10%).

[0081] In addition, Figure 5In the embodiment, the strip t is pasted on the lower end surface E1 and the upper end surface E2 respectively, but the strip t pasted on the stacked electrode body 20 can also be a single piece. In some embodiments, the strip t is preferably wound around the outer peripheral surface of the stacked electrode body 20 for more than one circle, except for the P1 portion of the lower end surface E1 opposite to the gas exhaust valve 13. Thus, the entire lower end surface E1 except for the P1 portion opposite to the gas exhaust valve 13, the entire upper end surface E2, the first flat surface F1 and the second flat surface are all covered with the strip t, thereby improving the workability when pasting the strip t. In addition, it is not easy to produce a step height difference between the first flat surface F1 and the second flat surface, and the surface pressure can be made uniform. It is even possible to suppress uneven reactions during charging and discharging.

[0082] The non-aqueous electrolyte is housed inside the battery case 10 together with the stacked electrode body 20. The non-aqueous electrolyte can be the same as that of a general non-aqueous electrolyte secondary battery and is not particularly limited. The non-aqueous electrolyte is a non-aqueous liquid electrolyte containing a non-aqueous solvent and a supporting salt. The non-aqueous solvent includes, for example, carbonates such as ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). The non-aqueous solvent is preferably a mixture of EC, EMC, and DMC in the range of 1 to 99% each so that the total ratio becomes 100%. The supporting salt is, for example, a fluorine-containing lithium salt. The fluorine-containing lithium salt preferably includes lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (F2LiNO4S2) called LiFSI, or a mixture thereof. The concentration of the supporting salt is preferably 0.6 to 1.8 mol per 1 L of the non-aqueous solvent. However, in other embodiments, the non-aqueous electrolyte is solid (solid electrolyte) and can be integrated with the stacked electrode body 20.

[0083] Battery 100 can be used in various applications, and can be suitably used as a power source (driving power source) for motors installed in vehicles such as cars and trucks. The type of vehicle is not particularly limited, and examples thereof include plug-in hybrid electric vehicles (PHEVs), hybrid electric vehicles (HEVs), and battery electric vehicles (BEVs).

[0084] Several embodiments related to the present invention are described below, but the present invention is not intended to be limited to these embodiments.

[0085] Battery Construction

[0086] First, a battery case with a gas discharge valve was prepared for each example. The positions and numbers of the gas discharge valves are shown in Tables 1 and Figures 6 to 16 Furthermore, the battery case of Examples 6, 7-1, 7-2, and 8-1 has Figure 4 The gas discharge valve has the shape shown in (A) (the center C of the gas discharge valve coincides with the center of gravity G of the lower surface of the battery case), and the battery case of Example 8-2 has Figure 4 (B) A gas discharge valve having a shape shown in FIG. 1 (the center C of the gas discharge valve is located at a position offset from the center of gravity G of the lower surface of the battery case).

[0087] Next, prepare the stacked electrode body, and stick the tape on the outer peripheral surface of the stacked electrode body under the conditions described in Table 1 to fix the stacked structure. Furthermore, at this time, for the example where "Presence of tape on the portion opposite to the gas exhaust valve" in Table 1 is "No", the tape is not stuck on the portion of the lower end face opposite to the gas exhaust valve. In addition, for the example where "Presence of tape on the portion vertically above the gas exhaust valve" in Table 1 is "Yes", the tape is stuck on the portion vertically above the gas exhaust valve in the upper end face to cover it with the tape. Figures 6 to 16 The positional relationship between the gas discharge valve and the strip in each example is shown in FIG. Then, the stacked electrode body is placed in a battery case, and a non-aqueous electrolyte is injected into the battery case to produce a prototype. Figure 3 The square battery shown.

[0088] Battery Evaluation

[0089] The prototype battery is put into a discharged state, and clamped with aluminum metal blocks with a thickness of 3 cm from the long sides of both sides through insulating materials or elastic bodies, and constrained with a constant pressure of 0.1 to 1 MPa. In addition, a hole of several mm in diameter is left in the center of the metal block (the center of gravity (center) of the long side of the battery) so that a nail can be inserted. The hole diameter is about +1 to 2 mm relative to the diameter of the nail. For example, if the diameter of the nail is 3 mm, the hole diameter is about 3.1 to 3.2 mm. Next, the battery clamped by the metal blocks is charged to full charge (SOC 100%). Then, the nail penetration test is carried out using the following steps.

[0090] In the nail penetration test, a specified nail is inserted through a hole in the center of a metal block, forcing the battery to short-circuit and raise its temperature. The test temperature is room temperature (approximately 25°C). A round nail, size N65 (φ3mm / shape, no angle requirement) manufactured by DAIDOHANT Co., Ltd. is used. The penetration speed is 1 mm / s, and the test is stopped when the battery enters a thermal runaway state.

[0091] The morphological changes of the batteries after the thermal runaway were evaluated using seven levels, from 1 to 7. The morphological changes of the batteries in each level were as follows. The results are shown in Table 1.

[0092] Level 1: Only the gas exhaust valve is open and the battery case remains unchanged

[0093] Level 2: The gas discharge valve is open, with cracks only around it, but no other changes to the battery case.

[0094] Level 3: The gas discharge valve is open, and there are cracks in three or more locations around it and in other battery cases, but there are no cracks at either terminal.

[0095] Level 4: The gas discharge valve is open, and there are 4 to 9 cracks around it and in other battery cases, but no cracks at the two terminals.

[0096] Level 5: The gas discharge valve is open, and there are 10 or more cracks around it and in other battery cases, and there are also cracks at both terminals.

[0097] Level 6: The gas discharge valve is open, and there are cracks in 10 or more locations around it and in other battery cases. In addition, there are cracks in both terminals, and one terminal surface is separated from the battery case.

[0098] Level 7: The gas discharge valve is open, and there are cracks in 10 or more locations around it and in the other battery cases. Furthermore, there are cracks in both terminals, and one terminal surface is separated from the battery case. In other words, more than 70 wt% of the contents have been scattered from the battery case to the outside (comparative example)

[0099]

[0100] First, compare Comparative Examples 1 and 2 in Table 1 with Comparative Examples 3-1 to 3-3. Comparative Example 1 is an example in which the gas exhaust valve is provided on the upper surface of the battery case. Comparative Example 2 is an example in which the gas exhaust valve is provided on both sides of the battery case (specifically, a pair of sealing plates). In both Comparative Examples 1 and 2, the battery morphology changes the most after thermal runaway, and exhibits a state of Level 7 (the lowest level) (see also Figure 7 Gas flows (arrows) (A) and (B). Although not intended to be particularly limiting, the reason for this is believed to be that when the gas discharge valve is provided on the upper surface or side of the battery case, the gas generated during thermal runaway is not easily cooled, resulting in a high gas temperature and / or high gas pressure, which may cause the battery case to crack and the contents to be scattered to the outside.

[0101] Comparative Examples 3-1 to 3-3 are examples in which the gas exhaust valve is provided on the lower surface of the battery case. Compared with Comparative Examples 1 and 2, Comparative Examples 3-1 to 3-3 relatively suppress the morphological changes of the battery after thermal runaway and show a state of grade 5 to 6 (see also Figure 8Gas flow (arrows) from (A) to (C). While not intended to be particularly limiting, the reason for this is believed to be that the gases generated during thermal runaway come into contact with the lower surface of the battery case and are cooled, suppressing increases in gas temperature and pressure. However, cracks were also observed at both terminals, so the effect of the disclosed technology cannot be considered sufficient.

[0102] In addition, Comparative Examples 3-1 and 3-2 are examples in which the gas discharge valve does not coincide with the center of gravity G of the lower surface of the battery case. Comparative Example 3-3 is an example in which the gas discharge valve coincides with the center of gravity G of the lower surface of the battery case. Among Comparative Examples 3-1 to 3-3, the morphological changes of the battery after thermal runaway are most suppressed in Comparative Example 3-3. Although it is not intended to be particularly limiting, the reason for this is that in Comparative Examples 3-1 and 3-2, a distribution of gas volume is generated within the battery, and due to the deviation of gas pressure, cracks are likely to occur in areas other than the gas discharge valve of the battery case, especially between the valves when there are two valves, and around the valve when there is only one valve, with cracks occurring in various parts of the battery case centered around the valve. On the other hand, in Comparative Example 3-3, it is believed that a distribution of gas volume within the battery is relatively unlikely to occur, and the deviation of gas pressure is small, so cracks are unlikely to occur in areas other than the gas discharge valve of the battery case.

[0103] Next, compare Examples 2-1 and 2-2 in Table 1 with Comparative Example 3-3. Example 2-1 is the same as Comparative Example 3-3 except that the strips are asymmetrically attached to the lower end surface E1 and the upper end surface E2. Compared with Comparative Example 3-3, Example 2-1 further suppresses the morphological changes of the battery after thermal runaway and shows a state of Level 4 (see also Figure 9 (A) Gas flow (arrow)). In addition, Example 2-2 is the same as Example 2-1 except that the upper part of the gas discharge valve in the upper end surface is covered with a tape. Compared with Example 2-1, Example 2-2 further suppresses the morphological change of the battery after thermal runaway and shows a level 3 state (also refer to Figure 9 (B) Gas flow (arrows). Although not intended to be particularly limiting, the reason for this is that the generated gas collides with the strip above the gas discharge valve in the vertical direction and tends to flow downward.

[0104] Next, let's compare Examples 3-1 and 3-2 in Table 1. Examples 3-1 and 3-2 are examples in which the width of the tape pasted on the upper end surface is wider than that of the tape pasted on the lower end surface, and the width of the tape pasted on the upper end surface is larger than that of the tape pasted on the lower end surface. Furthermore, in Example 3-1, the portion opposite to the gas exhaust valve is not covered by the tape, while in Example 3-2, the portion opposite to the gas exhaust valve is covered by the tape. Compared with Example 3-1, Example 3-2 relatively suppresses the morphological changes of the battery after thermal runaway and presents a state of Level 3 (also refer to Figure 10 (A) and (B) Gas flow (arrows).

[0105] Next, let's compare Examples 4-1 and 4-2 in Table 1. Examples 4-1 and 4-2 are examples where the tape is attached longer in the lamination direction at the upper end surface than in Examples 2-1 and 2-2. Compared to Example 4-1, Example 4-2 relatively suppressed the morphological changes of the battery after thermal runaway and exhibited a level 3 state (see also Figure 11 Gas flows (arrows) in (A) and (B). Although not intended to be particularly limiting, the reason for this is believed to be that the generated gas collides with the strip above the gas discharge valve in the vertical direction and tends to flow downward.

[0106] Next, Example 5 in Table 1 is an example in which the entire lower end surface except for the portion facing the gas exhaust valve is covered with a tape, and the entire upper end surface is covered with a tape. In Example 5, even compared with the previous examples, the morphological changes of the battery after thermal runaway were suppressed at a particularly high level, resulting in a good result (level 1) (see also Figure 6 Gas flow (arrows).

[0107] Next, let's compare Examples 6 to 8-2 in Table 1. The R1 of Example 6 (the ratio of the length of the portion not attached with the tape relative to the length from the center C of the gas exhaust valve to the outer edge) is 150%, the R1 of Examples 7-1 and 7-2 is 20%, and the R1 of Examples 8-1 and 8-2 is 50%. In Examples 7-1 and 7-2, the morphological changes of the battery after thermal runaway are relatively suppressed compared to Examples 6, 8-1, and 8-2, and the battery is in a state of level 1 or 2 (see also). Figure 12 、 Figure 13 (A), (B), Figure 14 Gas flows (arrows) in (A) and (B). Although not intended to be particularly limiting, the reason for this is believed to be that as the ratio of R1 decreases, the gas is more concentrated in the portion not covered by the strip, the momentum of the ejected gas increases, and the gas discharge valve can be opened at an early stage.

[0108] In addition, Example 7-2 is the same as Example 7-1, except that the lower and upper end surfaces are more extensively covered with a tape. In Example 7-2, the morphological changes of the battery after thermal runaway were suppressed at a particularly high level compared to Example 7-1, resulting in a good result (level 1). Although not intended to be particularly limiting, the reason for this is believed to be that the momentum of the generated gas colliding with the gas discharge valve increases, and the pressure around the gas discharge valve increases rapidly, thereby enabling the gas discharge valve to open at an early stage.

[0109] Furthermore, Example 8-2 is identical to Example 8-1, except that the center C of the gas discharge valve is offset from the center of gravity G of the lower surface of the battery case. The morphological change of the battery after thermal runaway in Example 8-2 was at the same level (level 3) as in Example 8-1. This indicates that as long as the gas discharge valve is positioned so as to coincide with the center of gravity G of the lower surface of the battery case, the same effect can be achieved even if the center C of the gas discharge valve is not aligned with the center of gravity G of the lower surface of the battery case.

[0110] Next, let's compare Examples 9 to 11 in Table 1 with Example 5. Example 9 is an example in which the tape is wound around the electrode body for more than one turn. The morphological change of the battery after thermal runaway in Example 9 is the same level as that in Example 5 (level 1). This shows that even if a single tape is used, as long as the entire lower end surface except for the portion facing the gas discharge valve is covered with the tape, and the entire upper end surface is covered with the tape, the same effect can be obtained (see also). Figure 15 (A) Gas flow (arrows). In addition, from the comparison of Example 9 (porosity 0%), Example 10 (porosity 20%), and Example 11 (porosity 40%), which have different porosity of the strips, it can be seen that the lower the porosity of the strip, the more the morphological changes of the battery after thermal runaway can be suppressed to a higher level (see also Figure 15 (B) Gas flow (arrows) The reason for this is that if there are pores in the strip, gas leaks through them, and thus the gas induction toward the gas discharge valve decreases.

[0111] Next, let's compare Examples 12 and 13 in Table 1 with Example 2-2. Example 12 is an example in which the coverage of the strip material on the upper end surface is larger (43%) than that of Example 2-2 (26%). As can be seen from the comparison between Example 12 and Example 2-2, the greater the coverage of the strip material on the upper end surface, the more the morphological changes of the battery after thermal runaway are suppressed (see also Figure 16 (A) Gas flow (arrow)). In addition, Example 13 is an example in which the strip coverage ratio of the portion of the lower end surface that is not opposite to the gas exhaust valve (non-opposite portion) is smaller (11%) than that of 2-2 (22%). The morphological change of the battery after thermal runaway in Example 13 is the same level (level 3) as that of Example 2-2. From this, it can be seen that as long as the strip coverage ratio of the non-opposite portion is 10% or more, the same effect can be obtained (also refer to Figure 16 (B) Gas flow (arrows).

[0112] The above describes the embodiments of the technology disclosed herein. However, the above description is merely illustrative and does not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples illustrated in the above description.

[0113] As described above, specific aspects of the technology disclosed herein include those described in the following items.

[0114] Item 1: A non-aqueous electrolyte secondary battery, comprising: a stacked electrode body having multiple positive electrodes and multiple negative electrodes; a non-aqueous electrolyte; and a battery case for accommodating the stacked electrode body and the non-aqueous electrolyte, the battery case having at least: a lower surface; a pair of side surfaces extending from a pair of edges of the lower surface and opposite to each other; and an upper surface opposite to the lower surface, a gas discharge valve being provided on the lower surface, the stacked electrode body having: a pair of flat surfaces opposite to the pair of side surfaces of the battery case; and a lower end surface opposite to the lower surface of the battery case and an upper end surface opposite to the upper surface of the battery case, the lower end surface and the upper end surface being the end surfaces where the stacked structure of the positive electrode and the negative electrode is exposed, and at least one strip is pasted on the stacked electrode body in a manner spanning the pair of flat surfaces, and the lower end surface and the upper end surface of the stacked electrode body are asymmetrically covered by the strip in a manner such that gas flows toward the gas discharge valve.

[0115] Item 2: The nonaqueous electrolyte secondary battery according to Item 1, wherein the gas exhaust valve is provided at a position that coincides with the center of gravity of the lower surface of the battery case.

[0116] Item 3: The nonaqueous electrolyte secondary battery according to Item 1 or 2, wherein an area of ​​the upper end surface covered by the tape material is larger than an area of ​​the lower end surface covered by the tape material.

[0117] Item 4: The nonaqueous electrolyte secondary battery according to any one of Items 1 to 3, wherein a portion of the upper end surface located vertically above the gas discharge valve is covered with the tape.

[0118] Item 5: A non-aqueous electrolyte secondary battery according to any one of Items 1 to 4, wherein at least one of the strips is pasted on the upper end surface and the lower end surface respectively, and the length of the strip pasted on the upper end surface extending along the flat surface of the stacked electrode body is longer than that of the strip pasted on the lower end surface.

[0119] Item 6: The nonaqueous electrolyte secondary battery according to any one of Items 1 to 5, wherein the entire lower end surface except for a portion facing the gas discharge valve is covered with the tape material, and the entire upper end surface is covered with the tape material.

[0120] Item 7: A non-aqueous electrolyte secondary battery according to any one of Items 1 to 5, wherein the portion of the lower end surface opposite to the gas exhaust valve is covered by the strip except for the portion opposite to the center portion of the gas exhaust valve, and the portion of the upper end surface located vertically above the center portion of the gas exhaust valve is covered by the strip.

[0121] Item 8: The nonaqueous electrolyte secondary battery according to any one of Items 1 to 5, wherein the tape is wound around the outer peripheral surface of the stacked electrode body for one or more turns, excluding a portion of the lower end surface facing the gas release valve.

[0122] Item 9: The non-aqueous electrolyte secondary battery according to any one of Items 1 to 8, wherein the tape is porous.

[0123] Item 10: A non-aqueous electrolyte secondary battery according to any one of Items 1 to 5, wherein the portion of the lower end surface opposite to the gas exhaust valve is not covered by the strip, and when the length of the portion not opposite to the gas exhaust valve in the direction along the side surface of the battery case is set to 100%, more than 10% of the length is covered by the strip.

Claims

1. A non-aqueous electrolyte secondary battery comprising: A stacked electrode body having a plurality of positive electrodes and a plurality of negative electrodes; a non-aqueous electrolyte; and a battery case accommodating the stacked electrode body and the non-aqueous electrolyte. The battery case has at least: a lower surface; a pair of side surfaces extending from a pair of edges of the lower surface and facing each other; and an upper surface opposite to the lower surface, A gas discharge valve is provided on the lower surface. The stacked electrode body has: a pair of flat surfaces opposite to the pair of side surfaces of the battery case; and a lower end surface opposite to the lower surface of the battery case and an upper end surface opposite to the upper surface of the battery case, the lower end surface and the upper end surface being end surfaces where the stacked structure of the positive electrode and the negative electrode is exposed, At least one tape is attached to the stacked electrode body so as to span the pair of flat surfaces. The lower end surface and the upper end surface of the stacked electrode body are asymmetrically covered by the tape material so that gas flows toward the gas discharge valve.

2. The nonaqueous electrolyte secondary battery according to claim 1, wherein The gas exhaust valve is provided at a position that coincides with the center of gravity of the lower surface of the battery case.

3. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein An area of ​​the upper end surface covered by the strip material is larger than an area of ​​the lower end surface covered by the strip material.

4. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein A portion of the upper end surface located vertically above the gas discharge valve is covered with the tape.

5. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein At least one strip of the strip is attached to the upper end surface and the lower end surface respectively. The tape material attached to the upper end surface extends along the flat surface of the stacked electrode body longer than the tape material attached to the lower end surface.

6. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein The entire lower end surface except for a portion facing the gas discharge valve is covered by the tape, and the entire upper end surface is covered by the tape.

7. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein The portion of the lower end surface facing the gas discharge valve is covered by the tape except for the portion facing the center of the gas discharge valve. A portion of the upper end surface located vertically above the center portion of the gas discharge valve is covered with the tape.

8. The nonaqueous electrolyte secondary battery according to claim 1 or 2, wherein The tape is wound around the outer peripheral surface of the stacked electrode body for one or more turns, excluding a portion of the lower end surface facing the gas release valve.

9. The nonaqueous electrolyte secondary battery according to claim 8, wherein The strip material is porous.

10. The non-aqueous electrolyte secondary battery according to claim 3, wherein The portion of the lower end surface facing the gas exhaust valve is not covered by the strip, and when the length of the portion not facing the gas exhaust valve along the side surface of the battery case is set to 100%, more than 10% of the length is covered by the strip.

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