JP2019153388A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

To provide a nonaqueous electrolyte secondary battery with improved operability of a gas exhaust part provided on a bottom of a case body.SOLUTION: A nonaqueous electrolyte secondary battery 10 according to one embodiment disclosed herein comprises: an electrode body 14 which is formed by winding a positive electrode 11, a negative electrode 12, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12; a case body 16 which houses the electrode body 14; a negative electrode tab 21 which electrically connects the negative electrode 12 to the case body 16; and a sealing body 17 which seals an opening on the case body 16. The negative electrode tab 21 has one end bonded to a winding start end of the negative electrode 12 and the other end bonded to a bottom inner face of the case body 16. At a bottom center of the case body 16, there is provided a gas exhaust part 30 which opens when internal pressure of the battery reaches a predetermined pressure.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a non-aqueous electrolyte secondary battery.

  Conventionally, when the internal pressure of the battery rises due to heat generation due to an internal short circuit, etc., a gas discharge part that opens when the internal pressure of the battery reaches a predetermined pressure is provided at the bottom of the battery case body to prevent the battery case from bursting. A non-aqueous electrolyte secondary battery is known (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 2018-14160

  By the way, in order to further improve the safety of the battery, there is a demand for a battery structure that improves the operability of the gas discharge part provided at the bottom of the case body when the battery internal pressure increases.

  Accordingly, an object of the present disclosure is to provide a nonaqueous electrolyte secondary battery in which the operability of a gas discharge unit provided at the bottom of the case body is improved.

  A nonaqueous electrolyte secondary battery according to one embodiment of the present disclosure includes a positive electrode, a negative electrode, and an electrode body in which a separator interposed between the positive electrode and the negative electrode is wound, a case main body that houses the electrode body, A negative electrode tab that electrically connects the negative electrode and the case main body; and a sealing body that seals an opening of the case main body. One end of the negative electrode tab is joined to the winding start end of the negative electrode. The other end is joined to the inner surface of the bottom of the case body, and a gas discharge portion that opens when the battery internal pressure reaches a predetermined pressure is provided at the center of the bottom of the case body.

  According to the present disclosure, it is possible to provide a nonaqueous electrolyte secondary battery in which the operability of the gas discharge unit provided at the bottom of the case body is improved.

It is sectional drawing of the nonaqueous electrolyte secondary battery which concerns on embodiment. It is a schematic plan view which shows the negative electrode of the state before winding. (A) is a partial expanded sectional view of the case main body bottom part of the nonaqueous electrolyte secondary battery shown in FIG. 1, (B) is a bottom view of the nonaqueous electrolyte secondary battery shown in FIG. It is a bottom view of the nonaqueous electrolyte secondary battery which is another example of this embodiment. It is sectional drawing of the conventional nonaqueous electrolyte secondary battery. It is a schematic diagram which shows an example of a structure of a battery module.

  Hereinafter, an example of the nonaqueous electrolyte secondary battery which is one embodiment of the present disclosure will be described. The drawings referred to in the description of the following embodiments are schematically described, and the dimensional ratios of the components drawn in the drawings may be different from the actual products.

  FIG. 1 is a cross-sectional view of the nonaqueous electrolyte secondary battery according to the embodiment. A non-aqueous electrolyte secondary battery 10 shown in FIG. 1 includes a wound electrode body 14 in which a positive electrode 11, a negative electrode 12, and a separator 13 interposed between the positive electrode 11 and the negative electrode 12 are wound, and a non-aqueous electrolyte. Insulating plates 18 and 19, a positive electrode tab 20, a negative electrode tab 21, and a battery case 15 respectively disposed above and below the electrode body 14.

  The battery case 15 includes, for example, a bottomed cylindrical case main body 16 having an opening, and a sealing body 17 that seals the opening of the case main body 16. The battery case 15 preferably includes a gasket 28 provided between the case main body 16 and the sealing body 17, thereby ensuring the airtightness inside the battery.

  The case main body 16 shown in FIG. 1 is a metal container which accommodates the electrode body 14, a nonaqueous electrolyte, etc., for example. The case body 16 preferably has an overhanging portion 22 that supports the sealing body 17 with a part of the side surface overhanging inward. The overhang portion 22 is formed in an annular shape along the circumferential direction of the case body 16, for example, and supports the sealing body 17 on the upper surface thereof. A gas discharge unit 30 is provided at the bottom center of the case body 16 shown in FIG. The gas discharge unit 30 will be described later.

  The sealing body 17 has, for example, a structure in which a filter 23, a lower valve body 24, an insulator 25, an upper valve body 26, and a cap 27 are stacked in this order from the electrode body 14 side. The members constituting the sealing body 17 have, for example, a disk shape or a ring shape, and the members other than the insulator 25 are electrically connected to each other. The lower valve body 24 and the upper valve body 26 are connected to each other at the central portion, and an insulator 25 is interposed between the peripheral portions. When the internal pressure rises due to heat generation due to an internal short circuit or the like, for example, the lower valve body 24 is deformed and broken so as to push up the upper valve body 26 toward the cap 27, and the current path between the lower valve body 24 and the upper valve body 26 is changed. Blocked. When the internal pressure further increases, the upper valve body 26 is broken and the gas is discharged from the opening of the cap 27.

  FIG. 2 is a schematic plan view showing the negative electrode in a state before winding. In FIG. 2, the left end portion in the longitudinal direction of the negative electrode 12 is a winding start end portion of the negative electrode 12 when forming the wound electrode body 14, and is an inner peripheral portion of the electrode body 14. The right end portion of the negative electrode 12 in the longitudinal direction is the winding end portion of the negative electrode 12 when forming the wound electrode body 14, and is the outer peripheral portion of the electrode body 14. As shown in FIG. 2, the negative electrode 12 includes a negative electrode current collector 32 and a negative electrode active material layer 34. The negative electrode 12 includes a coating part 36 in which a negative electrode active material layer 34 is formed on a negative electrode current collector 32 and a negative electrode current collector 32 in which the negative electrode active material layer 34 is not disposed on the negative electrode current collector 32. And an exposed portion 38 where the body 32 is exposed. The exposed portion 38 shown in FIG. 2 is disposed at the winding start end portion of the negative electrode 12, and is located on the inner peripheral portion of the electrode body 14 when the electrode body 14 is formed. The length of the exposed portion 38 is not particularly limited. For example, it is desirable that the length of the electrode body 14 is one or more rounds.

  As shown in FIG. 2, one end of the negative electrode tab 21 is provided on the exposed portion 38 located at the winding start end of the negative electrode 12. The negative electrode tab 21 and the exposed portion 38 are joined by welding or the like. As shown in FIG. 1, the negative electrode tab 21 extends from the negative electrode 12 through the through hole of the insulating plate 19 to the bottom inner surface of the case body 16 and the other end is joined to the bottom inner surface of the case body 16 by welding or the like. Has been. Thereby, the negative electrode 12 and the case main body 16 are electrically connected, and the case main body 16 becomes a negative electrode terminal. In the nonaqueous electrolyte secondary battery 10 shown in FIG. 1, the joint between the negative electrode tab 21 and the bottom inner surface of the case body 16 is provided in the region of the gas discharge portion 30 described later. If it is, it will not be restrict | limited in particular.

  Although not shown in the figure, the positive electrode 11 includes a positive electrode current collector and a positive electrode active material layer. Similarly to the negative electrode 12, the positive electrode 11 includes a coating portion in which a positive electrode active material layer is formed on a positive electrode current collector, and a positive electrode active material layer that is not disposed on the positive electrode current collector. And an exposed portion where the electric body is exposed. The exposed portion may be provided at any location of the positive electrode 11. One end of the positive electrode tab 20 shown in FIG. 1 is joined by welding or the like on an exposed portion provided in the central portion in the longitudinal direction of the positive electrode 11. The positive electrode tab 20 extends from the positive electrode 11 through the through hole of the insulating plate 18 to the filter 23, and the other end is joined to the lower surface of the filter 23 by welding or the like. Thereby, the cap 27 electrically connected to the filter 23 becomes a positive electrode terminal.

  FIG. 3A is a partially enlarged cross-sectional view of the bottom portion of the case body of the nonaqueous electrolyte secondary battery shown in FIG. FIG. 3B is a bottom view of the non-aqueous electrolyte secondary battery shown in FIG. 1, and is a view of the bottom portion of the case body shown in FIG. 1 viewed from the outside of the non-aqueous electrolyte secondary battery. As shown in FIGS. 1 and 3, a gas discharge portion 30 that opens when the battery internal pressure reaches a predetermined pressure is provided at the bottom center of the case body 16. Specifically, an annular groove 31 is formed at the bottom center of the case body 16, and a portion surrounded by the groove 31 is an area of the gas discharge unit 30. The center of the bottom of the case body 16 refers to a range of 30% from the center of the bottom, preferably 10% from the center of the bottom, with respect to the distance between the outer periphery and the center of the bottom.

  The groove 31 is, for example, an inscription formed from the outer surface side of the bottom portion of the case main body 16, and a portion where the groove 31 is formed in the bottom portion of the case main body 16 becomes a thin-walled portion that is thinner than other portions. . When the battery internal pressure reaches a predetermined pressure, the thin wall portion and the like are broken, and the gas discharge portion 30 is opened. The ratio of the thickness of the thin portion to the thickness of the bottom portion of the case body 16 is preferably 0.15 or less, for example, in consideration of durability during normal use and operability when the internal pressure is increased.

  The planar view shape of the groove 31 shown in FIG. 3 is a circular shape, but is not limited to this, and may be, for example, a C shape as shown in FIG. A polygonal shape or the like may be used. In the case of the C shape shown in FIG. 4, a portion surrounded by the groove 31 and a virtual straight line α that connects both ends of the groove 31 is an area of the gas discharge unit 30. In addition, the gas discharge part 30 is good also as a thin part which reduced the thickness of the whole area | region.

  The gas discharge unit 30 may be disposed at the center of the bottom of the case body 16, but is preferably disposed at the center of the bottom of the case body 16 and on the extension line of the core of the electrode body 14. The electrode body 14 is produced, for example, by winding the positive electrode 11, the negative electrode 12 and the separator 13 using a winding core. According to this method, the winding core portion of the electrode body 14 becomes a cavity. Since the core portion serving as the hollow portion functions as an exhaust path for the gas generated in the battery, the internal pressure of the battery is increased by arranging the gas discharge portion 30 on the extension line of the core portion of the electrode body 14. The operation of the gas discharge unit 30 at the time becomes easy.

  Thus, by providing the gas discharge part 30 in the center of the bottom of the case body 16, the gas discharge part 30 in the center of the bottom of the case body 16 opens when the battery internal pressure rises due to an internal short circuit or the like. Thus, the gas is discharged out of the battery system, so that the safety of the battery is achieved. In addition, in this embodiment, since gas is also discharged | emitted also from the sealing body 17 side as already stated, it has a safer battery structure.

  By the way, when the joining part of the negative electrode tab 21 and the bottom part of the case main body 16 is provided in the center of the bottom part of the case main body 16, that is, in the region of the gas discharge part 30 provided in the center of the bottom part of the case main body 16. In the case where the gas discharge part 30 is opened, the negative electrode tab 21 is pulled along with the opening of the gas discharge part 30. At this time, if the negative electrode tab 21 is caught on the electrode body 14 or the insulating plate 19 between the electrode body 14 and the bottom portion of the case body 16, the gas discharge portion 30 is difficult to open and the operability is lowered. However, since the negative electrode tab 21 in the present embodiment has a structure (hereinafter referred to as an inner tab structure) joined to the winding start end portion (the inner peripheral portion of the electrode body 14) of the negative electrode 12, the opening of the gas discharge portion 30 is provided. Accordingly, when the negative electrode tab 21 is pulled, the negative electrode tab 21 is hardly caught by the electrode body 14, the insulating plate 19, etc., so that the gas discharge unit 30 operates smoothly. If the joint between the negative electrode tab 21 having the inner tab structure and the bottom of the case body 16 is outside the region of the gas discharge part 30 at the center of the bottom part, the negative electrode tab is originally associated with the opening of the gas discharge part 30. Since 21 is not pulled, the gas discharge part 30 operates smoothly. That is, by using the negative electrode tab 21 having the inner tab structure, the operation of the gas discharge unit 30 at the center of the bottom portion of the case body 16 is possible regardless of where the joint portion between the negative electrode tab 21 and the bottom portion of the case body 16 is located. Is done smoothly.

  The joint between the negative electrode tab 21 and the bottom of the case body 16 is provided at the center of the bottom of the case body 16 in terms of workability when the negative electrode tab 21 is joined to the bottom of the case body 16, that is, the case It is preferable to be provided in the region of the gas discharge part 30 provided at the bottom center of the main body 16. When joining the negative electrode tab 21 to the bottom of the case body 16, for example, the negative electrode tab 21 and the case body 16 are sandwiched and welded from inside and outside of the case body 16 by a pair of welding electrodes. At this time, if the joint between the negative electrode tab 21 and the bottom of the case body 16 is set at the center of the bottom of the case body 16, the welding electrode inside the case body 16 is passed through the winding core (cavity) of the electrode body 14 to the negative electrode. Since it can contact | abut to the tab 21, joining work becomes easy.

  FIG. 5 is a cross-sectional view of a conventional nonaqueous electrolyte secondary battery. In the nonaqueous electrolyte secondary battery 40 shown in FIG. 5, the same reference numerals are given to the same configurations as those of the nonaqueous electrolyte secondary battery 10 of the present embodiment shown in FIG. In the nonaqueous electrolyte secondary battery 40 shown in FIG. 5, one end of the negative electrode tab 42 is at the end of winding of the negative electrode 12 (the outer peripheral portion of the electrode body 14) when forming the wound electrode body 14. It is the structure (henceforth an outer tab structure) joined. The negative electrode tab 42 extends from the negative electrode 12 to the bottom inner surface of the case body 16 through the outside of the insulating plate 19, and the other end is joined to the bottom inner surface of the case body 16. When the joint between the negative tab 42 having the outer tab structure and the bottom portion of the case body 16 is provided in the region of the gas discharge portion 30 at the center of the bottom portion, the negative tab 42 is compared with the inner tab structure. The length from one end of the electrode to the other end becomes long, and the negative electrode tab 42 easily interferes with the electrode body 14, the insulating plate 19, and the like. Therefore, when the negative electrode tab 42 of the outer tab structure is pulled along with the opening of the gas discharge part 30, the negative electrode tab 42 is easily caught on the electrode body 14, the insulating plate 19 and the like as compared with the case of the inner tab structure. Become. Therefore, the non-aqueous electrolyte secondary battery 40 using the negative tab 42 having the outer tab structure has a case main body 16 having a structure that is smaller than that of the non-aqueous electrolyte secondary battery 10 of the present embodiment using the negative tab 21 having the inner tab structure. The operability of the gas discharge part 30 at the bottom center is lowered.

  Hereinafter, the positive electrode 11, the negative electrode 12, the nonaqueous electrolyte, the separator 13, and the like will be described in detail.

  As the positive electrode current collector constituting the positive electrode 11, a metal foil that is stable in the potential range of the positive electrode such as aluminum, a film in which the metal is disposed on the surface layer, or the like is used.

  The positive electrode active material layer constituting the positive electrode 11 contains a positive electrode active material. The positive electrode active material layer preferably contains a conductive material and a binder in addition to the positive electrode active material.

  Examples of the positive electrode active material contained in the positive electrode active material layer include lithium transition metal composite oxides. Specifically, lithium cobaltate, lithium manganate, lithium nickelate, lithium nickel manganese composite oxide, lithium nickel cobalt A composite oxide or the like can be used, and Al, Ti, Zr, Nb, B, W, Mg, Mo, or the like may be added to these lithium transition metal composite oxides.

  Examples of the conductive material included in the positive electrode active material layer include carbon powder such as carbon black, acetylene black, ketjen black, and graphite. These may be used alone or in combination of two or more.

  Examples of the binder contained in the positive electrode active material layer include a fluorine-based polymer and a rubber-based polymer. For example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), or modified products thereof as fluorine-based polymers, ethylene-propylene-isoprene copolymer, ethylene-propylene-butadiene copolymer as rubber-based polymers Examples include coalescence. These may be used alone or in combination of two or more.

  As the negative electrode current collector 32 constituting the negative electrode 12, a metal foil stable in the potential range of the negative electrode such as copper, a film in which the metal is disposed on the surface layer, or the like can be used.

  The negative electrode active material layer 34 constituting the negative electrode 12 includes a negative electrode active material. The negative electrode active material layer 34 preferably includes a thickener and a binder in addition to the negative electrode active material.

  As the negative electrode active material, a carbon material capable of occluding and releasing lithium ions can be used, and in addition to graphite, non-graphitizable carbon, graphitizable carbon, fibrous carbon, coke, carbon black, and the like are used. Can do. Furthermore, silicon, tin, and alloys and oxides mainly containing these can be used as the non-carbon material.

  As the binder, PTFE or the like can be used as in the case of the positive electrode 11, but a styrene-butadiene copolymer (SBR) or a modified body thereof may be used. As the thickener, carboxymethyl cellulose (CMC) or the like can be used.

  The non-aqueous electrolyte includes, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The non-aqueous electrolyte is not limited to a liquid electrolyte, and may be a solid electrolyte using a gel polymer or the like. As the non-aqueous solvent, for example, carbonates, lactones, ethers, ketones, esters, a mixed solvent of two or more of these, and the like are used.

Examples of the electrolyte salt include a lithium salt. For example, LiPF ₆ , LiBF ₄ , LICF ₃ SO _3, a mixture of two or more of these, and the like are used. The amount of electrolyte salt dissolved in the solvent is, for example, 0.5 to 2.0 mol / L.

  For the separator 13, for example, a porous sheet having ion permeability and insulating properties is used. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. As a material of the separator 13, an olefin resin such as polyethylene or polypropylene, cellulose, or the like is preferable. The separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin resin. Moreover, the multilayer separator containing a polyethylene layer and a polypropylene layer may be sufficient, and what applied materials, such as an aramid resin and a ceramic, to the surface of a separator may be used.

  FIG. 6 is a schematic diagram illustrating an example of the configuration of the battery module. The battery module 44 shown in FIG. 6 has a plurality of nonaqueous electrolyte secondary batteries 10 according to the present embodiment, and the nonaqueous electrolyte secondary batteries 10 are parallel to each other in the axial direction on the same plane. It is arranged to be. The axial direction of the battery is a direction perpendicular to the gas discharge part 30 (see FIG. 1) at the bottom center of the case body 16. According to the non-aqueous electrolyte secondary battery 10 according to the present embodiment, the gas discharge part 30 provided at the center of the bottom of the case body 16 has high operability, so that the battery internal pressure is prevented from increasing and the battery case is ruptured. It is possible to prevent. Further, the gas in the battery is easily discharged from the gas discharge unit 30 (easily discharged in the axial direction of the battery). Therefore, by arranging the plurality of nonaqueous electrolyte secondary batteries 10 on the same plane so that the axial directions of the batteries are parallel, the temperature and internal pressure of the one or more nonaqueous electrolyte secondary batteries 10 can be reduced. Even if it rises suddenly for some reason, it is possible to suppress damage to the adjacent nonaqueous electrolyte secondary battery 10 as much as possible.

<Example>
[Production of positive electrode]
100 parts by mass of aluminum-containing nickel cobalt oxide (LiNi _0.88 Co _0.09 Al _0.03 O ₂ ) as a positive electrode active material and 1 part by mass of acetylene black (AB) as a conductive agent 0.9 parts by mass of polyvinylidene fluoride (PVDF) as an agent was mixed, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) was further added to prepare a positive electrode mixture slurry. Next, the positive electrode mixture slurry was applied to both surfaces of a positive electrode current collector made of aluminum foil, dried, and then rolled with a roller. Then, it cut | judged to the predetermined electrode size and produced the positive electrode by which the positive electrode active material layer was formed in both surfaces of the positive electrode electrical power collector.

[Production of negative electrode]
A mixture of graphite powder and Si oxide as the negative electrode active material was mixed so as to have a mass ratio of 95: 5. 100 parts by mass of this mixture, 1 part by mass of carboxymethyl cellulose (CMC) as a thickener, and 1 part by mass of styrene butadiene rubber (SBR) as a binder are mixed, and an appropriate amount of water is added. A negative electrode mixture slurry was prepared. Next, the negative electrode mixture slurry was applied to both surfaces of a negative electrode current collector made of copper foil, dried, and then rolled using a compression roller. This was cut into a predetermined electrode size to produce a negative electrode in which a negative electrode active material layer was formed on both sides of the negative electrode current collector.

[Preparation of non-aqueous electrolyte]
A non-aqueous electrolyte was prepared by dissolving 1 mol / L of LiPF ₆ in a mixed solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of 30:70.

[Production of non-aqueous electrolyte secondary battery]
A positive electrode tab made of aluminum was attached to the positive electrode, and a negative electrode tab made of nickel was attached to the negative electrode. The negative electrode tab was attached to the winding start end of the negative electrode. And the winding type electrode body was produced by winding a positive electrode and a negative electrode through the separator made from polyethylene. Insulating plates were arranged above and below the electrode body and housed in a case body having a gas discharge part at the center of the bottom. Next, the negative electrode tab was welded to the bottom inner surface of the case main body, in the region of the gas discharge portion provided in the center of the bottom of the case main body, and the positive electrode tab was welded to the sealing body. Then, after injecting the non-aqueous electrolyte into the case body, a gasket is interposed around the sealing body and attached inside the opening of the case body, and the opening of the case body is caulked inward, An electrolyte secondary battery was produced.

<Comparative example>
A nonaqueous electrolyte secondary battery was produced in the same manner as in the example except that the negative electrode tab was attached to the end of winding of the negative electrode, and was charged and discharged under the same conditions as in the example. This was used as a comparative battery.

<Heating test>
The batteries of Examples and Comparative Examples were charged to 4.2 V with a constant current of 0.3 It in an environment of 25 ° C., and then charged with a constant voltage of 4.2 V until the current became 0.02 It. The battery after charging was preheated in a constant temperature bath at 40 ° C. A thermocouple was welded to the preheated battery side surface, and it was put into a 50 mm diameter tubular furnace heated to 650 ° C. The time (operation time) from when the battery was put into the tubular furnace until the gas discharge part provided at the bottom of the case body was activated (opened) was measured. Further, after the battery was ignited, the battery was taken out from the tubular furnace, and the presence or absence of rupture of the side surface of the case body was visually confirmed. The number n of battery tests was set to 100, and the average value of the operation time of the gas discharge part, the variation (σ), and the burst occurrence rate on the side surface of the case main body were obtained. Table 1 shows the results.

  The average value and the variation of the operation time of the gas discharge part in the battery of the example showed a lower value than the battery of the comparative example. Moreover, the burst incidence rate of the case main body side surface in the battery of an Example also showed the value lower than a comparative example. Therefore, the non-aqueous electrolyte secondary battery in which the negative electrode tab is attached to the winding start end of the negative electrode and the negative tab of the inner tab structure is joined to the region of the gas discharge part provided at the bottom center of the case body is Compared with a non-aqueous electrolyte secondary battery in which the negative electrode tab is attached to the end of winding of the negative electrode and has an outer tab structure, and the negative electrode tab of the outer tab structure is joined to the gas discharge region provided at the bottom center of the case body. As a result, the operability of the gas discharge portion provided at the center of the bottom of the case body has been improved, and the safety of the battery has been improved.

DESCRIPTION OF SYMBOLS 10 Nonaqueous electrolyte secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 15 Battery case, 16 Case main body, 17 Sealing body, 18, 19 Insulation board, 20 Positive electrode tab, 21 Negative electrode tab, 22 Overhang part , 23 Filter, 24 Lower valve body, 25 Insulator, 26 Upper valve body, 27 Cap, 28 Gasket, 30 Gas discharge part, 31 Groove, 32 Negative electrode current collector, 34 Negative electrode active material layer, 36 Coating part, 38 Exposed portion, 40 non-aqueous electrolyte secondary battery, 42 negative electrode tab, 44 battery module.

Claims (2)

An electrode body in which a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode are wound,
A case main body for accommodating the electrode body;
A negative electrode tab for electrically connecting the negative electrode and the case body;
A sealing body for sealing the opening of the case body,
One end of the negative electrode tab is bonded to the winding start end of the negative electrode, and the other end is bonded to the bottom inner surface of the case body,
A non-aqueous electrolyte secondary battery in which a gas discharge part that opens when the battery internal pressure reaches a predetermined pressure is provided at the bottom center of the case body. The nonaqueous electrolyte secondary battery according to claim 1, wherein a joint portion between the negative electrode tab and the bottom inner surface of the case body is provided in a region of the gas discharge portion.