JP2023134035A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

To provide a non-aqueous electrolyte secondary battery capable of improving shock absorption performance and suppressing internal short circuits in a case of external impact.SOLUTION: The non-aqueous electrolyte secondary battery includes: a wound-type electrode body in which a positive electrode plate and a negative electrode plate are wound with a separator therebetween; and an exterior can accommodating the electrode body. The positive electrode plate includes: a positive tab that is joined to an exposed surface of a positive electrode core formed on at least a part of the positive electrode core in a longitudinal direction of the electrode plate and extends from one end of the positive electrode core in a short direction of the electrode plate; a protective tape 30 affixed to the positive electrode plate to cover the exposed surface and a portion of the positive tab that overlaps the exposed surface; and an outer tape 33 that is attached to the positive electrode plate so as to overlap the outside of the protective tape. The outer tape has at least one cut 34 extending in the longitudinal direction of the electrode plate at both ends, and the middle of the cut overlaps both ends E of the protective tape in the longitudinal direction of the electrode plate.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to non-aqueous electrolyte secondary batteries.

BACKGROUND ART Nonaqueous electrolyte secondary batteries have been known that include an electrode body in which a positive electrode plate and a negative electrode plate are wound together with a separator interposed therebetween, and an outer can containing the electrode body and an electrolyte. In recent years, the capacity of secondary batteries used in electric vehicles and the like has been increasing, and as the capacity of secondary batteries increases, the amount of heat generated when the battery is short-circuited internally is increasing. Therefore, there is a need to reduce the risk of internal short circuits. The positive electrode plate of the battery has an exposed surface where the surface of the positive electrode core body is exposed, and a positive electrode tab for current collection is bonded to the exposed surface.

Patent Document 1 discloses that an insulating protective tape is attached to a positive electrode plate while covering the positive electrode tab and the exposed surface of the positive electrode core, and that the protective tape has a tensile strength of a predetermined value or more and a puncture strength of a predetermined value or more. It is described that it has the following. This is said to improve the safety of the battery in a vertical crush test in which the measuring head is pressed in the longitudinal direction of the battery while the battery is standing upright.

Patent Document 2 discloses that an insulating protective tape is attached to the positive electrode plate while covering the positive electrode tab and the exposed surface of the positive electrode core, and prevents the separator from breaking due to a step at the end of the protective tape. For this reason, it is described that a notch should be made at the end of the protective tape.

JP2009-245650A International Publication No. 2020/241410

However, in the configurations disclosed in Patent Documents 1 and 2, there is room for improvement in terms of improving shock absorption performance and suppressing internal short circuits when shock is applied to the battery from the outside.

A non-aqueous electrolyte secondary battery according to the present disclosure includes: a wound-type electrode body in which a strip-shaped positive electrode plate and a strip-shaped negative electrode plate are wound with a separator interposed therebetween; and an outer can housing the electrode body. The positive electrode plate includes a positive electrode core, a positive electrode mixture layer formed on the surface of the positive electrode core, and a positive electrode mixture layer formed on the exposed surface of the positive electrode core formed on at least a portion of the positive electrode core in the longitudinal direction of the electrode plate. A positive electrode tab that is joined and extends from one end of the positive electrode core in the short direction of the electrode plate, a portion of the positive electrode tab that is overlapped with the exposed surface, and a protective tape that is affixed to the positive electrode plate so as to cover the exposed surface. , an outer tape attached to the positive electrode plate so as to overlap the outside of the protective tape, the outer tape having at least one cut extending in the longitudinal direction of the electrode plate at both ends in the longitudinal direction of the electrode plate, This is a non-aqueous electrolyte secondary battery in which the middle of the cut overlaps both ends of the protective tape in the longitudinal direction of the electrode plate.

According to the non-aqueous electrolyte secondary battery according to the present disclosure, by overlapping the protective tape and the outer tape, it is possible to improve the shock absorption performance for shocks applied to the separator from the positive electrode plate side when shocks are applied from outside the battery. . Furthermore, since the middle of the cut formed in the outer tape overlaps both ends of the protective tape, the outer tape can be made flexible so that both ends follow the deformation of the electrode body. Thereby, when an impact is applied from outside the battery, it is possible to suppress the angular stepped portion of the outer tape from being pressed against the separator. Therefore, breakage of the separator can be suppressed, and internal short circuits of the battery can be suppressed.

FIG. 1 is a cross-sectional view along the axial direction of a non-aqueous electrolyte secondary battery according to an example of an embodiment. FIG. 1 is a schematic development view of a positive electrode plate that constitutes a non-aqueous electrolyte secondary battery according to an example of an embodiment. 3 is an enlarged view of part A in FIG. 2. FIG. 3 is a sectional view taken along line BB in FIG. 2 with some parts omitted; FIG.

Embodiments according to the present invention will be described in detail below with reference to the accompanying drawings. In the following description, specific shapes, materials, numerical values, directions, etc. are illustrative to facilitate understanding of the present invention, and may be changed as appropriate according to the specifications of the non-aqueous electrolyte secondary battery. . Further, in the following, the term "abbreviation" is used to include, for example, not only the case where they are completely the same, but also the case where they can be considered to be substantially the same. Furthermore, when a plurality of embodiments and modifications are included below, it is assumed from the beginning that their characteristic parts will be used in combination as appropriate.

FIG. 1 is a cross-sectional view along the axial direction of a non-aqueous electrolyte secondary battery 10 according to an embodiment. FIG. 2 is a schematic development view of the positive electrode plate 11 that constitutes the non-aqueous electrolyte secondary battery 10. As illustrated in FIG. 1, the nonaqueous electrolyte secondary battery 10 includes a wound electrode body 14, a nonaqueous electrolyte (not shown), an outer can 15, and a sealing body 16. The wound electrode body 14 has a strip-shaped positive electrode plate 11, a strip-shaped negative electrode plate 12, and a strip-shaped separator 13, and the positive electrode plate 11 and the negative electrode plate 12 are spirally wound with the separator 13 in between. has been done. Hereinafter, one axial side of the electrode body 14 may be referred to as "upper", and the other axial side may be referred to as "lower". The non-aqueous electrolyte includes a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. The nonaqueous electrolyte is not limited to a liquid electrolyte, and may be a solid electrolyte using a gel polymer or the like.

Referring to FIG. 2, the positive electrode plate 11 includes a strip-shaped positive electrode core 11a and a positive electrode tab 19 joined to the positive electrode core 11a. The positive electrode tab 19 is a conductive member for electrically connecting the positive electrode core 11a and the positive electrode terminal, and extends from the upper end of the positive electrode core 11a to one side (upper side) in the axial direction α of the electrode body 14. It's out. The positive electrode tab 19 is provided, for example, approximately at the center of the electrode body 14 in the radial direction β. The positive electrode tab 19 is a strip-shaped conductive member. The constituent material of the positive electrode tab is not particularly limited. It is preferable that the positive electrode tab 19 is made of a metal whose main component is aluminum. Further, in the positive electrode plate 11, a positive electrode mixture layer 11b is formed on each of the inner surface (radially inner surface) and the outer surface (radially outer surface) of the positive electrode core 11a. In FIG. 2, the positive electrode mixture layer 11b is shown as a thin sandy area.

The negative electrode plate 12 has a strip-shaped negative electrode core and a negative electrode tab 20 joined to the negative electrode core. The negative electrode tab 20 is a conductive member for electrically connecting a negative electrode core and an exterior can 15 described below, and is located on the other side (lower side) of the electrode body 14 in the axial direction α from the lower end of the negative electrode core. It has extended to The outer can 15 serves as a negative electrode terminal. The negative electrode tab 20 is provided, for example, on the inner side portion (inner peripheral side portion) of the electrode body 14 . The negative electrode tab 20 is a strip-shaped conductive member. The constituent material of the negative electrode tab is not particularly limited. It is preferable that the negative electrode tab is made of a metal mainly composed of nickel or copper, or a metal containing both nickel and copper. Further, in the negative electrode plate 12, a negative electrode mixture layer is formed on each of the inner surface (radially inner surface) and outer surface (radially outer surface) of the negative electrode core.

Further, the negative electrode core is exposed on the outermost peripheral surface of the electrode body 14 and is electrically connected to the outer can 15 by contacting the inner surface of the cylindrical portion 15a of the outer can 15. This electrical connection between the negative electrode plate 12 and the cylindrical portion 15a of the outer can 15 ensures even better current collection performance.

As described above, the electrode body 14 has a wound structure in which the positive electrode plate 11 and the negative electrode plate 12 are spirally wound with the separator 13 in between. The positive electrode plate 11, the negative electrode plate 12, and the separator 13 are all formed in a band shape, and are wound in a spiral shape so that they are alternately stacked in the radial direction β of the electrode body 14. In the electrode body 14, the longitudinal direction of each electrode plate is the winding direction, and the width direction of each electrode plate is the axial direction α.

In the example shown in FIG. 1, the outer can 15 and the sealing body 16 constitute a metal battery case that houses the electrode body 14 and the nonaqueous electrolyte. Insulating plates 17 and 18 are provided above and below the electrode body 14, respectively. The positive electrode tab 19 extends toward the sealing body 16 through the through hole of the upper insulating plate 17, and is welded to the lower surface of the filter 22, which is the bottom plate of the sealing body 16. In the non-aqueous electrolyte secondary battery 10, the cap 26, which is the top plate of the sealing body 16 electrically connected to the filter 22, serves as a positive terminal.

The outer can 15 is a bottomed cylindrical metal container having an opening, for example, a bottomed cylindrical shape. A gasket 27 is provided between the outer can 15 and the sealing body 16 to ensure airtightness within the outer can 15. The outer can 15 has a grooved portion 21 formed by, for example, spinning a side portion from the outside to the inside in the radial direction. The grooved portion 21 is preferably formed in an annular shape along the circumferential direction of the outer can 15, and supports the sealing body 16 on its upper surface. The sealing body 16 seals the opening of the outer can 15.

The sealing body 16 includes a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26, which are laminated in order from the electrode body 14 side. Each member constituting the sealing body 16 has, for example, a disk shape or a ring shape, and each member except the insulating member 24 is electrically connected to each other. The lower valve body 23 and the upper valve body 25 are connected to each other at their central portions, and an insulating member 24 is interposed between their peripheral edges. When the internal pressure of the battery increases due to abnormal heat generation, for example, the lower valve body 23 breaks, and the upper valve body 25 swells toward the cap 26 and separates from the lower valve body 23, thereby cutting off the electrical connection between the two. When the internal pressure further increases, the upper valve body 25 breaks and gas is discharged from the opening 26a of the cap 26.

Furthermore, in this embodiment, as shown in FIGS. 2 to 4, in order to improve the shock absorption performance when shock is applied from outside the battery and to suppress internal short circuits, the positive electrode tab 19 and A protective tape 30 is provided to protect the exposed surface 11c of the positive electrode core 11a, and an outer tape 33 is superimposed on the outside of the protective tape 30 and adhered to the positive electrode plate 11. Furthermore, the middle of the cuts 34 at both ends of the outer tape 33 overlaps both ends E of the protective tape 30.

Hereinafter, the overlapping structure of the electrode body 14, the protective tape 30 of the positive electrode plate 11, and the outer tape 33 will be described in detail with reference to FIGS. 2 to 4. FIG. 3 is an enlarged view of section A in FIG. 2. FIG. 4 is a sectional view taken along line BB in FIG. 2 with some parts omitted.

Referring to FIG. 2, the positive electrode plate 11 includes a strip-shaped positive electrode core 11a and positive electrode mixture layers 11b formed on both surfaces of the positive electrode core 11a. For the positive electrode core body 11a, for example, a foil of metal such as aluminum, a film with the metal disposed on the surface, or the like is used. A suitable positive electrode core 11a is a metal foil containing aluminum or an aluminum alloy as a main component. The thickness of the positive electrode core 11a is, for example, 10 μm to 30 μm.

It is preferable that the positive electrode mixture layer 11b contains a positive electrode active material, a conductive agent, and a binder. The positive electrode plate 11 is prepared by applying a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, and a solvent such as N-methyl-2-pyrrolidone (NMP) to both sides of a positive electrode core 11a, and then drying and It is produced by rolling.

Examples of positive electrode active materials include lithium-containing transition metal oxides containing transition metal elements such as Co, Mn, and Ni. The lithium-containing transition metal oxide is not particularly limited, but has the general formula Li _1+x MO ₂ (wherein -0.2<x≦0.2, M includes at least one of Ni, Co, Mn, and Al). A complex oxide represented by is preferable.

Examples of the conductive agent include acetylene black (AB), carbon black (CB) such as Ketjen black, and carbon materials such as graphite. Examples of the binder include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide (PI), acrylic resins, and polyolefin resins. It will be done. Furthermore, these resins may be used in combination with carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), or the like. These may be used alone or in combination of two or more.

In a part of the positive electrode plate 11 in the longitudinal direction (direction of the arrow γ), for example, approximately at the center, the surface of the metal constituting the positive electrode core 11a is exposed over the entire length in the short direction (direction of the arrow δ) of the positive electrode plate 11. An exposed surface 11c is formed. The exposed surface 11c is a portion to which the positive electrode tab 19 is bonded, and is a portion where the surface of the positive electrode core 11a is not covered with the positive electrode mixture layer 11b.

Note that the exposed surface 11c of the positive electrode core 11a may be formed at a location other than the center in the longitudinal direction γ of the electrode plate, and may be formed, for example, near the end portion in the longitudinal direction γ of the electrode plate. The exposed surface 11c is provided, for example, by intermittent coating without applying the positive electrode mixture slurry to a part of the positive electrode core 11a.

The positive electrode tab 19 is joined to the exposed surface 11c by, for example, ultrasonic welding, and extends from one end (upper end) of the positive electrode core body 11a in the short direction δ of the electrode plate. As shown in FIG. 4, the positive electrode tab 19 is formed in a band shape with a substantially rectangular cross section.

Furthermore, the portion of the positive electrode tab 19 that overlaps the exposed surface 11c and the exposed surface 11c are covered with a protective tape 30. The protective tape 30 is attached to the surface of the positive electrode plate 11, more specifically, to the surface of the positive electrode mixture layer 11b arranged on both sides in the longitudinal direction γ of the electrode plate with the exposed surface 11c in between. The protective tape 30 is an insulating tape having insulation properties. As a result, short circuit between the positive electrode plate 11 and the negative electrode plate 12 is prevented. It is preferable that the protective tape 30 covers the entire exposed surface 11c of the positive electrode core 11a, as shown in FIG.

The exposed surface 11c of the positive electrode core 11a is formed at the same position in the longitudinal direction γ of the electrode plate, for example, on both sides of the inside and outside of the winding of the positive electrode core 11a. When exposed surfaces 11c are formed on both sides of the inside and outside of the winding, the exposed surfaces 11c on the side to which the positive electrode tab is not joined are also covered with the protective tape attached to the positive electrode plate 11. The exposed surface 11c may be provided only on one of the inner side and the outer side of the positive electrode core 11a for bonding the positive electrode tab.

Furthermore, an outer tape 33 overlaps the outer side of the protective tape 30 covering the positive electrode tab 19. Like the protective tape 30, the outer tape 33 is also an insulating tape having insulation properties. For example, the outer tape 33 is made of the same material as the protective tape 30. Both ends of the outer tape 33 protrude from both sides of the protective tape 30 in the longitudinal direction γ of the electrode plate, and both ends protrude from the positive electrode plate 11, more specifically, both sides of the electrode plate longitudinal direction γ across the exposed surface 11c. The positive electrode mixture layer 11b is attached to the surface of the positive electrode mixture layer 11b.

As shown in FIG. 4, the protective tape 30 is an adhesive tape having a base layer 30a and an adhesive layer 30b formed on one surface of the base layer 30a. For example, a heat-resistant layer containing inorganic particles such as metal oxides can be provided between the base layer 30a and the adhesive layer 30b. The base material layer 30a may be any insulating resin, such as PPS (polyphenylene sulfide), PEEK (polyether ether ketone), PI (polyimide), PP (polypropylene), PET (polyethylene terephthalate), PBT ( polybutylene terephthalate), etc. can be used.

Adhesive layer 30b is provided to adhere protective tape 30 to the surface of positive electrode plate 11. The adhesive layer 30b can include at least one of a rubber-based polymer and an acrylic-based polymer. For example, a silicone polymer may be further added to the adhesive layer 30b.

Like the protective tape 30, the outer tape 33 is also an adhesive tape having a base layer 33a and an adhesive layer 33b formed on one surface of the base layer 33a. Examples of materials applicable to the base layer 33a and the adhesive layer 33b are the same as those for the protective tape 30.

The outer tape 33 is preferably disposed on the outside of the protective tape 30 in a portion including at least the center of the positive electrode plate 11 in the electrode plate transverse direction δ. Furthermore, the outer tape 33 is disposed on the outside of the protective tape 30 at least in a region centered on the center of the positive electrode plate 11 in the electrode plate transverse direction δ and including a range where the length in the electrode plate transverse direction δ is 10 mm. It is more preferable that

Furthermore, as shown in FIGS. 2 and 3, the outer tape 33 has a plurality of cuts 34 at both ends of the electrode plate longitudinal direction γ, which are lined up in the electrode plate transverse direction δ and extend in the electrode plate longitudinal direction γ. A cut group 35 having the following is formed. Each cut 34 of the cut group 35 opens at the outer end of the outer tape 33 in the longitudinal direction γ of the electrode plate.

Furthermore, the middle of each cut 34 of each cut group 35 overlaps both ends E of the protective tape 30 in the longitudinal direction γ of the electrode plate. Thereby, as will be described later, it is possible to improve the shock absorption performance when shock is applied from outside the battery, and to suppress internal short circuits. Note that the outer tape 33 may be configured to have only one cut 34 extending in the electrode plate longitudinal direction γ at both ends of the electrode plate longitudinal direction γ. On the other hand, from the viewpoint of imparting flexibility to both ends of the outer tape 33 as will be described later, it is preferable that a plurality of cuts 34 be formed at each of these ends.

The negative electrode plate 12 includes a strip-shaped negative electrode core and negative electrode mixture layers formed on both sides of the negative electrode core. For the negative electrode core, for example, a foil of metal such as copper, a film with the metal disposed on the surface layer, or the like is used. The thickness of the negative electrode core is, for example, 5 μm to 30 μm.

The negative electrode mixture layer preferably contains a negative electrode active material and a binder. The negative electrode plate 12 is produced by, for example, applying a negative electrode mixture slurry containing a negative electrode active material, a binder, water, etc. to both sides of a negative electrode core, and then drying and rolling the slurry.

The negative electrode active material is not particularly limited as long as it can reversibly occlude and release lithium ions, and examples thereof include carbon materials such as natural graphite and artificial graphite, metals that alloy with lithium such as Si and Sn, or these materials. An alloy containing , a composite oxide, etc. can be used. For example, the same resin as in the case of the positive electrode plate 11 is used as the binder contained in the negative electrode mixture layer. When preparing a negative electrode mixture slurry using an aqueous solvent, styrene-butadiene rubber (SBR), CMC or a salt thereof, polyacrylic acid or a salt thereof, polyvinyl alcohol, etc. can be used. These may be used alone or in combination of two or more.

For the separator 13, a porous sheet having ion permeability and insulation properties is used. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. The material for the separator 13 is preferably an olefin resin such as polyethylene or polypropylene. The thickness of the separator 13 is, for example, 10 μm to 50 μm. The separator 13 tends to become thinner as batteries increase in capacity and output. The separator 13 has a melting point of, for example, about 130°C to 180°C.

Then, a tape (not shown) is attached to the outermost circumferential surface of the negative electrode plate 12 so as to fix the winding end of the negative electrode plate 12 to the outermost circumferential surface of the negative electrode plate 12, which is the outermost circumferential surface of the electrode body 14. be done.

According to the above-mentioned non-aqueous electrolyte secondary battery 10, the impact absorption performance for the impact applied to the separator 13 from the positive electrode plate 11 side when an impact is applied from outside the battery due to overlapping of the protective tape 30 and the outer tape 33. can be improved. Specifically, as shown in FIG. 4, by overlapping the outer tape 33 on the outside of the protective tape 30, the adhesive layer 30b of the protective tape 30, its base layer 30a, and the outer tape are removed from the positive electrode plate 11 side. Since the 33 adhesive layers 33b and their base material layers 33a are arranged in this order, the total thickness of the adhesive layers 30b and 33b can be increased. Thereby, the above-mentioned impact absorption performance can be improved. On the other hand, in order to improve shock absorption performance, it may be possible to increase the thickness of the protective tape itself, but in that case, the thickness of the adhesive layer will be reduced by increasing the thickness of the base material layer. It is difficult to increase the thickness to the same extent. For this reason, in a configuration in which the thickness of the protective tape itself is increased, there is room for improvement in terms of improving shock absorption performance.

Furthermore, by overlapping the middle of the cut 34 formed in the outer tape 33 with both ends E of the protective tape 30, both ends of the outer tape 33 can be made flexible so as to follow the deformation of the electrode body 14. . Thereby, when an impact is applied from outside the battery, it is possible to suppress the angular stepped portion of the outer tape 33 from being pressed against the separator 13. Therefore, breakage of the separator 13 can be suppressed, and internal short circuits of the battery can be suppressed.

This will be explained in more detail using FIG. 4. Since both ends of the outer tape 33 are on the positive electrode mixture layer 11b, a step is formed at the P position in FIG. Furthermore, there is a possibility that a bent portion may be formed at the Q position in FIG. 4 at both ends of the outer tape 33 that overlap the both ends E of the protective tape 30 in the longitudinal direction γ of the electrode plate. Therefore, if this part is not flexible, when the electrode body 14 is deformed due to an impact applied from outside the battery, it will not be able to sufficiently follow the deformation, resulting in an inflexible angular bent part or step. The portion is pressed against the separator 13. In the embodiment, cuts are formed at both ends of the outer tape 33, as indicated by the range L1 in FIG. 4, and the middle of the cuts overlaps both ends E of the protective tape 30. As a result, flexibility is imparted to the bent portion and the step portion at the P position, so that breakage of the separator 13 facing these portions can be suppressed. Therefore, internal short circuits in the battery can be suppressed.

Further, it is preferable that the outer tape 33 is disposed on the outside of the protective tape 30 in a portion including at least the center of the positive electrode plate 11 in the electrode plate transverse direction δ. When an external impact is applied to the battery, the electrode body 14 is easily deformed near the center in the axial direction, and the separator 13 is likely to receive force from near the center of the positive electrode plate 11 in the short direction of the electrode plate. According to the above preferred configuration, the outer tape 33 is easily disposed near the portion of the separator 13 that is likely to receive force from the positive electrode plate 11, so that the effect of suppressing breakage in the separator 13 becomes significant.

In addition, in this preferred configuration, the outer tape 33 is arranged on the outside of the protective tape 30 in a range where the length in the electrode plate width direction δ is 10 mm, centered at least on the center of the electrode plate width direction δ of the positive electrode plate 11. It is more preferable to arrange it in a part containing. In the case of this configuration, the outer tape 33 is more likely to be disposed near a portion of the separator 13 that is likely to receive force from the positive electrode plate 11, so that the effect of suppressing breakage of the separator 13 becomes more pronounced.

The inventor of the present disclosure fabricated a total of 12 types of secondary batteries, Examples 1-5 and Comparative Examples 1-7, under the conditions shown in Table 1 below, conducted an impact test under predetermined conditions, and found that The presence or absence of breakage of the separator 13 was evaluated.

[Example 1]
[Preparation of positive electrode plate 11]
As a positive electrode active material, aluminum-containing lithium nickel cobalt oxide represented by LiNi _0.88 Co _0.09 Al _0.03 O ₂ was used. Then, 100 parts by mass of LiNi _0.88 Co _0.09 Al _0.03 O ₂ , 1 part by mass of acetylene black, and 0.9 parts by mass of polyvinylidene fluoride (PVDF) (binder) were mixed. Then, an appropriate amount of N-methyl-2-pyrrolidone (NMP) was added to prepare a positive electrode mixture slurry. Next, a positive electrode mixture slurry was applied intermittently to both sides of a long positive electrode core made of aluminum foil with a thickness of 15 μm so that an exposed surface of the core with a width of 7 mm in the longitudinal direction of the electrode plate was formed. . Thereafter, NMP is removed by heat treatment at a temperature of 100 to 150° C. in a heated dryer, and then rolled using a roller and cut into a predetermined size, and the positive electrode mixture is coated on both sides of the positive electrode core 11a. A positive electrode plate 11 on which a layer 11b was formed was produced. At this time, the thickness of the positive electrode plate 11 was 0.144 mm, the width was 62.6 mm, and the length was 860 mm. Thereafter, one end portion of an aluminum positive electrode tab 19 was fixed to the core exposed surface of the positive electrode plate 11 by welding.

[Application of protective tape 30 and outer tape 33]
Next, a protective tape 30 for protecting the positive electrode tab 19 was attached to the positive electrode mixture layer 11b of the positive electrode plate 11 so as to cover the positive electrode tab 19 and the exposed surface of the core. Next, on the outside of the protective tape 30, an outer tape 33 was overlaid on the central part of the electrode plate in the transverse direction. At this time, the tape height H, which is the length of the outer tape 33 in the transverse direction of the electrode plate, the tape width W, which is the length of the outer tape in the longitudinal direction, and the cut length D, shown in FIG. , H=20 mm, W=15 mm, and D=2 mm. Further, the tape width of the protective tape 30 in the longitudinal direction of the electrode plate was 12 mm. The outer tape 33 was placed outside the protective tape 30 so that its center coincided with the center of the positive electrode plate 11 in the short direction of the electrode plate. As a result, similarly to the example shown in FIG. 3, the middle of the cut 34 at both ends of the outer tape 33 overlaps both ends E of the protective tape 30, that is, the middle of the cut in Table 1 and the both ends of the protective tape overlap. Overlapping is "present". Moreover, the cut interval is 1 mm.

[Preparation of negative electrode plate 12]
As the negative electrode active material, a mixture of 95 parts by mass of graphite powder and 5 parts by mass of silicon oxide was used. Then, 100 parts by mass of the negative electrode active material, 1 part by mass of styrene-butadiene rubber (SBR) as a binder, and 1 part by mass of carboxymethyl cellulose (CMC) as a thickener were mixed. Then, this mixture was dispersed in water to prepare a negative electrode mixture slurry. Next, a negative electrode mixture slurry was applied intermittently to both sides of a long negative electrode core made of copper foil with a thickness of 8 μm so that an exposed surface of the core with a width of 7 mm in the longitudinal direction of the electrode plate was formed. . Then, after drying in a heated dryer, the negative electrode was compressed using a compression roller so that the thickness of the negative electrode was 0.160 mm, and cut into a predetermined size to form a negative electrode mixture layer on both sides of the negative electrode core. A negative electrode plate 12 was prepared. At this time, the width of the negative electrode plate 12 was 64.2 mm, and the length was 959 mm. Then, at one longitudinal end of the negative electrode plate 12, at the end located on the winding start side of the electrode body 14, an exposed part where no mixture layer is present and the core surface is exposed is provided, and the exposed part A negative electrode tab 20 made of nickel and having a width of 3.5 mm was fixedly attached by welding.

[Preparation of electrode body 14]
The produced positive electrode plate 11 and negative electrode plate 12 are spirally wound with a separator 13 made of a microporous polyethylene membrane interposed therebetween to produce a wound type electrode body 14, and the end of the winding is wrapped with tape. Fixed. At this time, the negative electrode core exposed portion was configured to cover the outermost periphery of the electrode body 14.

[Preparation of non-aqueous electrolyte]
5 parts by mass of vinylene carbonate (VC) was added to 100 parts by mass of a mixed solvent in which ethylene carbonate (EC) and dimethyl carbonate (DMC) were mixed at a volume ratio of EC:DMC=1:3. , LiPF ₆ was dissolved at a concentration of 1.5 mol/L to prepare a non-aqueous electrolyte.

[Preparation of secondary battery]
The above electrode body 14 is housed in a cylindrical outer can 15 with a bottom, insulating plates 28 and 29 are arranged above and below the electrode body 14, respectively, and a non-aqueous electrolyte is introduced into the outer can 15 using a reduced pressure method. Injected by Thereafter, the sealing body 16 was caulked and fixed to the open end of the outer can 15 via the gasket 27, thereby producing a cylindrical nonaqueous electrolyte secondary battery 10. At this time, the capacity of the battery was 4600mAh.

[Comparative example 1]
In Comparative Example 1, the outer tape overlapped with the protective tape 30 covering the positive electrode tab of the positive electrode plate was omitted. In Comparative Example 1, the other configurations are the same as in Example 1.

[Example 2-5, Comparative Example 2-7]
In each of Example 2-5 and Comparative Example 2-7, the tape height, tape width, cut length, cut interval, cut middle, and both ends of the protective tape 30 of the outer tape layered on the outside of the protective tape 30 were determined. This is the same as in Example 1 except that the presence or absence of overlap is configured as shown in Table 1. Specifically, in Example 2, the tape height was changed from Example 1 to 10 mm. In Example 3, the cut interval was changed from Example 1 to 0.5 mm. In Example 4, the cut interval was changed from Example 1 to 2 mm. In Example 5, the tape width was changed from Example 1 to 13 mm.

In Comparative Examples 2 and 3, the cut lengths were changed from Example 1 to 0.5 mm and 1 mm, respectively, so there was no overlap between the middle of the cut and both ends of the protective tape 30. In Comparative Example 4, the cut in Example 1 was omitted, so there was no overlap between the middle of the cut and both ends E of the protective tape 30. In Comparative Example 5, the tape width was changed from Example 1 to 12 mm, so there was overlap between the tip of the cut and both ends of the protective tape, but there was no overlap between the middle of the cut and both ends of the protective tape. In Comparative Example 6, the tape width was changed from Example 1 to 16 mm, so there was overlap between the back end of the cut and both ends of the protective tape, but there was no overlap between the middle of the cut and both ends of the protective tape. In Comparative Example 7, the tape width was changed to 17 mm, so there was no overlap between the cut and both ends of the protective tape.

[Test method]
[Impact test 1]
The non-aqueous electrolyte secondary batteries of Example 1-5 and Comparative Example 1-7 were charged to 4.2 V by constant current charging at 0.3 C in a 25° C. atmosphere. After that, as impact test 1, a metal round bar with a diameter of 15.8 mm was placed in the center of the battery, and a 9.1 kg weight was dropped from a height of 61 cm, in accordance with the T6 impact test of UN transportation test conditions. went. After the test, it was confirmed whether the battery ignited or not.

[Impact test 2]
Furthermore, using the non-aqueous electrolyte secondary batteries of Example 1-5 and Comparative Example 1-7, an impact test 2 was conducted in the same manner as impact test 1 without injecting the electrolyte into the battery case. I did it. Then, the battery after the test was disassembled, and the presence or absence of breakage of the separator 13 facing both ends of the protective tape 30 and the outer tape 33 was checked.

[Test results]
Table 1 shows the test results of impact tests 1 and 2. As shown in Table 1, in Comparative Example 1, which does not have the outer tape itself, and Comparative Examples 2-5 and 7, in which there is no overlap between the middle of the cut and both ends of the protective tape, ignition was observed in Impact Test 1; In No. 2, breakage of the separator was also observed. In Comparative Example 6, in which only the back end of the cut overlapped with both ends of the protective tape, no ignition was observed in Impact Test 1, but breakage of the separator was observed in Impact Test 2.

On the other hand, in Example 1-5 in which the middle of the cut overlapped with both ends of the protective tape, no ignition was observed in impact test 1, and no breakage of the separator 13 was observed in impact test 2. The reason for this is thought to be that the middle of the cut overlaps both ends E of the protective tape 30, thereby imparting flexibility to the angular and stepped portions of the outer tape 33 caused by the ends E. This confirmed the effects of the embodiment.

The exposed surfaces 11c of the positive electrode core 11a may be formed at a plurality of positions in the longitudinal direction γ of the positive electrode plate 11, and the positive electrode tabs 19 may be joined to each exposed surface 11c. Further, the protective tape described in the embodiment and an outer tape outside the protective tape may be provided on the positive electrode plate so as to cover each positive electrode tab 19 and exposed surface 11c.

Reference Signs List 10 nonaqueous electrolyte secondary battery, 11 positive electrode plate, 11a positive electrode core, 11b positive electrode mixture layer, 11c exposed surface, 12 negative electrode plate, 13 separator, 14 electrode body, 15 outer can, 15a cylindrical part, 16 sealing body, 17, 18 insulating plate, 19 positive electrode tab, 20 negative electrode tab, 21 grooved part, 22 filter, 23 lower valve element, 24 insulating member, 25 upper valve element, 26 cap, 27 gasket, 30 protective tape, 33 outer tape, 34 break, 35 break group.

Claims (3)

A wound type electrode body in which a band-shaped positive electrode plate and a band-shaped negative electrode plate are wound with a separator interposed therebetween;
an outer can housing the electrode body,
The positive electrode plate is
a positive electrode core;
a positive electrode mixture layer formed on the surface of the positive electrode core;
a positive electrode tab joined to an exposed surface of the positive electrode core formed on at least a portion of the positive electrode core in the longitudinal direction of the electrode plate, and extending from one end of the positive electrode core in the short direction of the electrode plate;
a protective tape affixed to the positive electrode plate so as to cover a portion of the positive electrode tab overlaid on the exposed surface and the exposed surface;
an outer tape attached to the positive electrode plate so as to overlap the outer side of the protective tape,
The outer tape has at least one cut extending in the longitudinal direction of the electrode plate at both ends in the longitudinal direction of the electrode plate,
The middle of the cut overlaps both ends of the protective tape in the longitudinal direction of the electrode plate,
Nonaqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to claim 1,
The outer tape is disposed on the outside of the protective tape at least in a portion including the center of the positive electrode plate in the short direction of the electrode plate.
Nonaqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery according to claim 2,
The outer tape is disposed on the outside of the protective tape in a portion including at least a range centered on the center of the positive electrode plate in the width direction of the electrode plate and having a length of 10 mm in the width direction of the electrode plate. ,
Nonaqueous electrolyte secondary battery.

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