WO2022202270A1

WO2022202270A1 - Cylindrical battery

Info

Publication number: WO2022202270A1
Application number: PCT/JP2022/009872
Authority: WO
Inventors: 学大竹; 翔太矢冨
Original assignee: 三洋電機株式会社; パナソニックホールディングス株式会社
Priority date: 2021-03-24
Filing date: 2022-03-08
Publication date: 2022-09-29

Abstract

This cylindrical battery (10) comprises a bottomed cylindrical outer can (16), a wound electrode body (14) stored inside the outer can (16), a sealing body (17) which closes off an opening of the outer can (16), and an upper insulating plate (18) which is disposed inside the outer can (16) and is positioned between the sealing body (17) and the electrode body (14) in an axial direction. The upper insulating plate (18) has, on a lower surface (51) on the electrode body (14) side in the axial direction, an annular first groove, and a plurality of second grooves extending from the radially inside to the outside in the substantially radial direction toward the first groove side.

Description

cylindrical battery

The present disclosure relates to cylindrical batteries.

Conventionally, there is one described in Patent Document 1 as a cylindrical battery. In this cylindrical battery, an insulating plate is placed between the sealing body and the electrode body to prevent electrical connection between the negative electrode of the electrode body and the sealing body. In addition, in this cylindrical battery, the sealing body is provided with an exhaust valve for exhausting high-temperature gas generated in the electrode body when the battery abnormally heats up, and the through hole for passing the gas to the sealing body side is insulated. placed on the board. This through-hole is also used for passing a positive electrode lead that electrically connects the positive electrode and the sealing member, and for immersing the electrolyte in the electrode assembly.

Japanese Patent Application Laid-Open No. 2008-103131

In order to increase the capacity of the battery, it is necessary to increase the size of the electrode assembly. However, as the electrode assembly becomes larger, the amount of gas generated when the battery abnormally heats up also increases. It is necessary to increase the strength of the insulating plate in order to ensure the through holes. However, if the strength of the insulating plate is increased, the outer edge of the insulating plate is likely to crack when the battery is subjected to an external force such as when the battery is dropped and deformed.

Furthermore, in order to increase the capacity of the battery, increasing the density of the electrode material by increasing the thickness of the mixture layer, thinning the current collector and separator, and increasing the density of the electrode material reduces the voids inside the battery. The impregnability of the electrolyte during battery production is likely to deteriorate.

Therefore, an object of the present disclosure is to provide a cylindrical battery in which the electrode body is less likely to be damaged by damage to the insulating plate, and in which the discharge performance of the gas generated when the battery abnormally heats up and the impregnation of the electrolyte into the electrode body can be improved. to do.

In order to solve the above problems, the cylindrical battery of the present disclosure includes a bottomed cylindrical outer can, a wound electrode body housed in the outer can, a sealing body for closing the opening of the outer can, and an outer package. an insulating plate arranged in the can and positioned between the sealing body and the electrode body in the axial direction, the insulating plate having an annular first groove and a radial and a plurality of second grooves extending substantially radially outward from the inner side to the first groove side.

According to the cylindrical battery according to the present disclosure, the electrode body is less likely to be damaged by damage to the insulating plate, and the discharge performance of the gas generated when the battery abnormally heats up and the impregnation of the electrode body with the electrolyte can be improved.

1 is an axial cross-sectional view of a cylindrical battery according to an embodiment of the present disclosure; FIG. FIG. 4 is a plan view of the upper insulating plate viewed from the outside in the axial direction; FIG. 2B is a cross-sectional view taken along line AA of FIG. 2A; FIG. 8 is a plan view of the upper insulating plate of Example 2 when viewed from the outside in the axial direction; FIG. 3B is a cross-sectional view taken along the line BB of FIG. 3A; FIG. 11 is a plan view of the upper insulating plate of Example 3 when viewed from the outside in the axial direction; 4B is a cross-sectional view taken along line CC of FIG. 4A; FIG. FIG. 11 is a plan view of the upper insulating plate of Example 4 when viewed from the outside in the axial direction; FIG. 5B is a cross-sectional view taken along line DD of FIG. 5A; FIG. 11 is a plan view of the upper insulating plate of Example 5 when viewed from the outside in the axial direction; 6B is a cross-sectional view taken along line EE of FIG. 6A; FIG. 10 is a plan view of the upper insulating plate of Comparative Example 1 when viewed from the outside in the axial direction; FIG. 7B is a cross-sectional view taken along line FF of FIG. 7A; FIG. 8 is a plan view of the upper insulating plate of Comparative Example 2 when viewed from the outside in the axial direction; FIG. FIG. 8B is a cross-sectional view taken along line GG of FIG. 8A; 10 is a plan view of the upper insulating plate of Comparative Example 3 when viewed from the outside in the axial direction; FIG. 9B is a cross-sectional view taken along line HH of FIG. 9A; FIG.

Hereinafter, embodiments of the cylindrical battery according to the present disclosure will be described in detail with reference to the drawings. Note that the cylindrical battery of the present disclosure may be a primary battery or a secondary battery. Also, a battery using an aqueous electrolyte or a battery using a non-aqueous electrolyte may be used. A non-aqueous electrolyte secondary battery (lithium ion battery) using a non-aqueous electrolyte is exemplified below as the cylindrical battery 10 of one embodiment, but the cylindrical battery of the present disclosure is not limited to this.

When multiple embodiments and modifications are included in the following, it is assumed from the outset that these features will be appropriately combined to construct a new embodiment. Further, in the following embodiments, the same reference numerals are given to the same configurations in the drawings, and redundant explanations are omitted. In addition, a plurality of drawings include schematic diagrams, and the dimensional ratios of length, width, height, etc. of each member do not necessarily match between different drawings. In this specification, for convenience of explanation, the axial (height) side of the sealing body 17 of the cylindrical battery 10 is referred to as "top", and the axial bottom side of the outer can 16 is referred to as "bottom". In addition, among the constituent elements described below, constituent elements that are not described in independent claims indicating the highest concept are optional constituent elements and are not essential constituent elements.

FIG. 1 is an axial cross-sectional view of a cylindrical battery 10 according to one embodiment of the present disclosure. As shown in FIG. 1, a cylindrical battery 10 includes a wound electrode body 14, a non-aqueous electrolyte (not shown), and a bottomed cylindrical metal outer can containing the electrode body 14 and the non-aqueous electrolyte. 16, and a sealing member 17 that closes the opening of the outer can 16. The electrode body 14 has a structure in which a long positive electrode 11 and a long negative electrode 12 are wound with two long separators 13 interposed therebetween.

The negative electrode 12 is formed with a size one size larger than that of the positive electrode 11 in order to prevent deposition of lithium. That is, the negative electrode 12 is formed longer than the positive electrode 11 in the longitudinal direction and the width direction (transverse direction). Also, the two separators 13 are at least one size larger than the positive electrode 11, and are arranged so as to sandwich the positive electrode 11, for example. The negative electrode 12 may constitute the winding start end of the electrode body 14 . Generally, however, the separator 13 extends beyond the winding start end of the negative electrode 12 , and the winding start end of the separator 13 becomes the winding start end of the electrode body 14 .

The non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. Examples of the non-aqueous solvent include esters, ethers, nitriles, amides, and mixed solvents of two or more thereof. The non-aqueous solvent may contain a halogen-substituted product obtained by substituting at least part of the hydrogen atoms of these solvents with halogen atoms such as fluorine. The non-aqueous electrolyte is not limited to a liquid electrolyte, and may be a solid electrolyte using a gel polymer or the like. A lithium salt such as LiPF ₆ is used as the electrolyte salt.

The positive electrode 11 has a positive electrode current collector and positive electrode mixture layers formed on both sides of the positive electrode current collector. As the positive electrode current collector, a metal foil stable in the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film in which the metal is arranged on the surface layer can be used. The positive electrode mixture layer contains a positive electrode active material, a conductive agent, and a binder. For the positive electrode 11, for example, a positive electrode mixture slurry containing a positive electrode active material, a conductive agent, a binder, and the like is applied onto a positive electrode current collector, the coating film is dried, and then compressed to collect a positive electrode mixture layer. It can be produced by forming on both sides of the electric body.

The positive electrode active material is composed mainly of a lithium-containing metal composite oxide. Metal elements contained in the lithium-containing metal composite oxide include Ni, Co, Mn, Al, B, Mg, Ti, V, Cr, Fe, Cu, Zn, Ga, Sr, Zr, Nb, In, Sn , Ta, W, and the like. An example of a preferable lithium-containing metal composite oxide is a composite oxide containing at least one of Ni, Co, Mn and Al.

Carbon materials such as carbon black, acetylene black, ketjen black, and graphite can be exemplified as the conductive agent contained in the positive electrode mixture layer. Examples of the binder contained in the positive electrode mixture layer include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. . These resins may be used in combination with cellulose derivatives such as carboxymethyl cellulose (CMC) or salts thereof, polyethylene oxide (PEO), and the like.

The negative electrode 12 has a negative electrode current collector and negative electrode mixture layers formed on both sides of the negative electrode current collector. For the negative electrode current collector, a metal foil stable in the potential range of the negative electrode 12, such as copper or a copper alloy, or a film in which the metal is arranged on the surface layer can be used. The negative electrode mixture layer contains a negative electrode active material and a binder. For the negative electrode 12, for example, a negative electrode mixture slurry containing a negative electrode active material, a binder, and the like is applied onto a negative electrode current collector, the coating film is dried, and then compressed to form a negative electrode mixture layer on the current collector. It can be produced by forming on both sides.

A carbon material that reversibly absorbs and releases lithium ions is generally used as the negative electrode active material. Preferred carbon materials are graphite such as natural graphite such as flake graphite, massive graphite and earthy graphite, massive artificial graphite and artificial graphite such as graphitized mesophase carbon microbeads. The negative electrode mixture layer may contain a Si material containing silicon (Si) as a negative electrode active material. In addition, a metal other than Si that forms an alloy with lithium, an alloy containing the metal, a compound containing the metal, or the like may be used as the negative electrode active material.

As in the case of the positive electrode 11, the binder contained in the negative electrode mixture layer may be fluororesin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like, but preferably styrene-butadiene rubber (SBR ) or its modified form. The negative electrode mixture layer may contain, for example, CMC or its salt, polyacrylic acid (PAA) or its salt, polyvinyl alcohol, etc. in addition to SBR or the like.

A porous sheet having ion permeability and insulation is used for the separator 13 . Specific examples of porous sheets include microporous thin films, woven fabrics, and non-woven fabrics. Polyolefin resins such as polyethylene and polypropylene, cellulose, and the like are preferable as the material of the separator 13 . The separator 13 may have either a single layer structure or a laminated structure. A heat-resistant layer or the like may be formed on the surface of the separator 13 .

As shown in FIG. 1, the positive electrode lead 20 is electrically connected to an intermediate portion such as the center portion in the winding direction of the positive electrode current collector, and the negative electrode lead 21 is connected to the end of the winding direction of the negative electrode current collector. It is electrically connected to the end. However, the negative electrode lead may be electrically connected to the winding start end of the negative electrode current collector in the winding direction. Alternatively, the electrode body has two negative leads, one negative lead is electrically connected to the winding start end of the negative electrode current collector in the winding direction, and the other negative lead is connected to the negative electrode current collector. may be electrically connected to the winding end portion in the winding direction of the . Alternatively, the negative electrode and the outer can may be electrically connected by bringing the winding end portion of the negative electrode current collector in the winding direction into contact with the inner surface of the outer can.

The cylindrical battery 10 has an upper insulating plate 18 above the electrode assembly 14 and a lower insulating plate 19 below the electrode assembly 14 . The positive electrode lead 20 extends through the first through hole 55 (see FIG. 2A) of the upper insulating plate 18 toward the sealing member 17 , and the negative electrode lead 21 extends through the outside of the lower insulating plate 19 to the bottom of the outer can 16 . It extends to the 68 side. The positive lead 20 is connected to the lower surface of the terminal plate 23, which is the bottom plate of the sealing member 17, by welding or the like, and the sealing plate 26, which is the top plate of the sealing member 17 electrically connected to the terminal plate 23, serves as a positive electrode terminal. The negative electrode lead 21 is connected to the inner surface of the bottom portion 68 of the outer can 16 by welding or the like, and the outer can 16 serves as a negative electrode terminal.

The cylindrical battery 10 further includes a resin gasket 27 arranged between the outer can 16 and the sealing member 17 . The gasket 27 is sandwiched between the outer can 16 and the sealing member 17 to insulate the sealing member 17 from the outer can 16 . The gasket 27 serves as a sealing material for keeping the inside of the battery airtight and as an insulating material for insulating the outer can 16 and the sealing body 17 . The outer can 16 has an annular grooved portion 34 in a portion of the cylindrical outer peripheral surface in the axial direction.

The grooved portion 34 can be formed, for example, by spinning a portion of the outer peripheral surface of the cylinder radially inward to recess it radially inward. The outer can 16 has a bottomed tubular portion 30 including a grooved portion 34 and an annular shoulder portion 38 . The bottomed tubular portion 30 accommodates the electrode assembly 14 and the non-aqueous electrolyte, and the shoulder portion 38 is bent radially inward from the opening-side end of the bottomed tubular portion 30 to reach the inner side. extends to The shoulder portion 38 is formed when the upper end portion of the outer can 16 is bent inward and crimped to the peripheral edge portion 45 side of the sealing member 17 . The sealing member 17 is crimped and fixed to the outer can 16 via the gasket 27 between the shoulder portion 38 and the grooved portion 34 . Thus, the internal space of the cylindrical battery 10 is sealed.

The outer diameter of the outer can 16 changes with the grooved portion 34 as a boundary. Specifically, the radial outer diameter of the sealing portion 41 that accommodates the sealing member 17 in the outer can 16 is smaller than the radial outer diameter of the body portion 42 that accommodates the electrode body 14 in the outer can 16 . It's becoming The sealing portion 41 is positioned axially above the grooving portion 34 , and the body portion 42 is positioned axially below the grooving portion 34 .

The outer can 16 can be produced, for example, as follows. First, a metal member having a bottom and a substantially cylindrical shape is produced from a flat steel plate by drawing the steel plate. After that, the lower insulating plate 19, the electrode body 14 to which the two leads 20 and 21 are joined, and the upper insulating plate 18 are inserted in this order into this metal member. Next, the end portion of the metal member on the opening side in the axial direction is deformed radially inward using a diameter reducing die to reduce the diameter. After that, the gasket 27 and the sealing member 17 are arranged at the portion where the diameter is reduced and the diameter becomes small. Subsequently, a spinning process is applied to the periphery of the portion of the metal member where the outer diameter varies to form the grooving portion 34 . Finally, the outer can 16 is manufactured by bending the end portion of the metal member on the opening side radially inward to form the shoulder portion 38 .

The sealing body 17 has a structure in which a terminal plate 23, a lower valve body 24a, an insulating member 25, an upper valve body 24b, and a sealing plate 26 are layered in this order from the electrode body 14 side. The lower valve body 24 a and the upper valve body 24 b constitute the exhaust valve 24 . Each member constituting the sealing member 17 has, for example, a disk shape or a ring shape, and each member other than the insulating member 25 is electrically connected to each other. Terminal plate 23 has at least one through hole 23a. In addition, the lower valve body 24a and the upper valve body 24b are connected at their central portions, and an insulating member 25 is interposed between their peripheral edge portions.

When the cylindrical battery 10 generates abnormal heat and the internal pressure of the cylindrical battery 10 rises, the lower valve body 24a deforms and breaks so as to push the upper valve body 24b upward toward the sealing plate 26, thereby separating the lower valve body 24a and the upper valve body 24b. A current path between the valve bodies 24b is cut off. When the internal pressure further increases, the upper valve body 24b is broken and the gas is discharged from the through hole 26a of the sealing plate 26. As shown in FIG. This gas discharge prevents the cylindrical battery 10 from bursting due to an excessive rise in the internal pressure of the cylindrical battery 10, thereby enhancing the safety of the cylindrical battery 10. FIG.

Next, the structure of the upper insulating plate 18 will be described in detail. The upper insulating plate 18 is made of resin. As shown in FIG. 1 , the upper insulating plate 18 has a groove 60 in a lower surface 51 on the axially lower side (an end surface on the electrode body 14 side in the axial direction). 2A is a plan view of the upper insulating plate 18 viewed from below in the axial direction, and FIG. 2B is a cross-sectional view taken along the line AA of FIG. 2A. As shown in FIGS. 2A and 2B, groove 60 includes first groove 61 and a plurality of second grooves 62 . The first groove 61 is an annular groove that is substantially circular in plan view when viewed from below in the axial direction, and extends in the circumferential direction of the cylindrical battery 10 . As shown in FIG. 2B, the first groove 61 has a shape in which the width in the radial direction gradually decreases toward the upper side in the axial direction, and the tip of the upper side in the axial direction is sharp.

As shown in FIG. 2A, the second groove 62 extends substantially radially outward from the radially inner side toward the first groove 61 side. It is preferable that the angles formed by the two second grooves 62 are substantially the same in all pairs of the two second grooves 62 adjacent in the circumferential direction. However, a plurality of sets composed of two second grooves 62 adjacent in the circumferential direction may have two or more sets in which the angles formed by the two second grooves 62 are not substantially the same. The cross-sectional shape of the second groove 62 taken along a plane including the width direction and the axial direction of the second groove 62 may be any shape, such as a rectangular shape or a semicircular shape. The plurality of second grooves 62 radially extend in the radial direction. Each second groove 62 communicates with the first groove 61 on the radially outer side. The two or more second grooves 62 merge at the radial center portion of the upper insulating plate 18, and the two or more second grooves 62 communicate with each other at the radial center portion.

As shown in FIG. 2A, the upper insulating plate 18 has a semicircular first through hole 55 as an example of a lead insertion hole. The first through-hole 55 is provided in the upper insulating plate 18 to allow the positive electrode lead 20 to pass therethrough and to flow high-temperature gas generated in the electrode assembly 14 toward the sealing member 17 when the cylindrical battery 10 generates abnormal heat. Also, the first through hole 55 is provided to allow the non-aqueous electrolyte (for example, electrolytic solution) injected from above to flow toward the body portion 42 .

In plan view when viewed from the axial direction, the opening area of the first through hole 55 is ⅓ or more and ½ or less of the area of the region surrounded by the outer edge 59 of the upper insulating plate 18 . An arcuate inner edge 55a of the first through hole 55 extends substantially in the circumferential direction. The upper insulating plate 18 further has one or more second through holes 56 . The opening area of the second through hole 56 is smaller than the opening area of the first through hole 55 . The second through hole 56 is provided in the upper insulating plate 18 in order to uniformly and quickly fill the body portion 42 with a non-aqueous electrolyte (for example, electrolytic solution) injected from above. Note that the shape of the opening of the first through hole 55 is not limited to a semicircular shape, and may be any shape. In addition, in plan view when viewed from the axial direction, the opening area of the first through hole may be less than 1/3 or larger than 1/2 of the area of the region surrounded by the outer edge of the upper insulating plate. good. Also, the upper insulating plate may not have the above-described second through holes.

As described above, according to the cylindrical battery 10, since the upper insulating plate 18 has the annular first groove 61, the force from the outer can 16 is applied to the upper insulating plate 18 when the cylindrical battery 10 is dropped or the like. In this case, the upper insulating plate 18 can be split along the thin first grooves 61, and irregular splitting of the upper insulating plate 18 can be suppressed or prevented. That is, when an external force acts on the upper insulating plate 18, it is possible to suppress or prevent fragments of the upper insulating plate 18 from scattering toward the electrode assembly 14 side. Therefore, in order to prevent the upper insulating plate 18 from melting and blocking at least a portion of the first through hole 55 serving as a gas exhaust hole when the cylindrical battery 10 is abnormally heated, the upper insulating plate 18 is made of a material that is difficult to melt and hard. , it is possible to suppress or prevent the electrode body 14 from being damaged by a fragment of the upper insulating plate 18, and to suppress or prevent the occurrence of a short circuit due to such damage.

In addition, the non-aqueous electrolyte can be caused to flow radially along the first grooves 61, and the non-aqueous electrolyte can be evenly and quickly filled in the circumferential direction. Furthermore, since the upper insulating plate 18 has a plurality of second grooves 62 extending substantially radially outward from the radially inner side to the first grooves 61 side, the outer can 16 is filled from the opening side. A non-aqueous electrolyte (eg, electrolytic solution) can also flow radially along the second grooves 62 . Therefore, the non-aqueous electrolyte can be filled more uniformly and quickly in the radial direction. Therefore, the non-aqueous electrolyte can be impregnated into the electrode assembly 14 more uniformly and quickly.

In addition, the radial outer diameter of the sealing portion 41 that accommodates the sealing member 17 in the outer can 16 is smaller than the radial outer diameter of the body portion 42 that accommodates the electrode body 14 in the outer can 16 .

When increasing the capacity of a cylindrical battery, it is generally necessary to increase the outer diameter of the sealing body as the diameter of the outer can increases. Therefore, it is necessary to increase the thickness of the part material to ensure strength. However, such an increase in the thickness of the component material leads to an increase in the weight of the cylindrical battery and an increase in the cost of the cylindrical battery.

On the other hand, according to the above configuration, the capacity can be increased without changing the inner diameter of the sealing portion 41, so the opening of the outer can 16 can be sealed using the existing sealing member 17 having sufficient strength. can. Therefore, it is possible not only to ensure sufficient strength of the sealing member 17, but also to suppress an increase in the weight and cost of the cylindrical battery 10. FIG. Furthermore, since the sealing body 17 can be shared by a plurality of cylindrical batteries having different capacities, the sealing body 17 can be mass-produced, and the cost of the cylindrical battery 10 can be further reduced.

Also, the second groove 62 communicates with the first groove 61 .

According to the above configuration, the nonaqueous electrolyte flowing in the circumferential direction along the first groove 61 can be caused to flow in the radial direction along the second groove 62, and vice versa. The radially flowing non-aqueous electrolyte can also be caused to flow in the circumferential direction along the first grooves 61 . Therefore, the non-aqueous electrolyte can be more uniformly and quickly filled in the circumferential and radial directions, and as a result, the non-aqueous electrolyte can be impregnated into the electrode assembly 14 more uniformly and quickly. In addition, unlike this configuration, the annular first groove does not have to communicate with the radially extending second groove.

In addition, the opening area of the first through hole 55 is ⅓ or more of the area of the region surrounded by the outer edge of the upper insulating plate 18 in plan view when viewed in the axial direction.

According to the above configuration, it is possible to smoothly flow high-temperature gas to the sealing member 17 side when the cylindrical battery 10 is abnormally heated. Moreover, the positive electrode lead 20 can be easily joined to the terminal plate 23 using the first through hole 55, and the non-aqueous electrolyte can be impregnated into the electrode body 14 more uniformly and quickly.

Further, the first groove 61 has a shape in which the width in the radial direction gradually decreases toward the upper side in the axial direction, and the tip of the first groove 61 in the upper side in the axial direction has a sharp shape. Therefore, when an excessive external force is applied, cracking of the upper insulating plate 18, which occurs at the tip of the axially upper side of the first groove 61, is likely to occur. Therefore, the cracking of the upper insulating plate 18 can be controlled more precisely, and damage to the electrode body 14 by fragments of the upper insulating plate 18 can be almost certainly prevented.

<Electrolyte penetration test, flat plate crushing test, and combustion test>
The inventor of the present application subjected the cylindrical batteries of Examples 1 to 5 and the cylindrical batteries of Comparative Examples 1 to 3 to the flat plate crushing test and the combustion test, which will be described below. It goes without saying that the cylindrical battery of the present disclosure is not limited to the cylindrical batteries of Examples 1 to 5. For example, the dimensions and materials of the upper insulating plate of the cylindrical battery of the present disclosure are Needless to say, the size and material of the upper insulating plate are not limited.

[Cylindrical battery of Example 1]
(Preparation of upper insulating plate)
An upper insulating plate 18 having a plan view seen from below in the axial direction shown in FIG. 2A and a cross-sectional view taken along the line AA of FIG. 2A in FIG. 2B was manufactured. Specifically, a disc-shaped insulator made of phenolic resin (GP) mixed with glass fiber and having an outer diameter of 20 mm and a thickness of 0.3 mm was placed at a position 2 mm inward from the outer periphery of the insulator with a width of 0.1 mm and a depth of 0. An annular first groove (notch) 61 of .2 mm was provided. In addition, a plurality of radial second grooves (notches) 62 with a width of 0.1 mm and a depth of 0.1 mm extending from the center of the insulator toward the annular first groove 61 were formed in the disk-shaped insulator. . The first groove 61 and the second groove 62 are communicated. Further, the disk-shaped insulator is further provided with the first through-hole 55 and the plurality of second through-holes 56 .

(Preparation of positive electrode)
Li(Ni _0.8 Co _0.15 Al _0.05 )O ₂ was used as a positive electrode active material. A positive electrode active material 100 (weight ratio), polyvinylidene fluoride 2.0 (weight ratio) as a binder, and acetylene black 2.0 (weight ratio) as a conductive agent are mixed with a liquid component (NMP) to form a positive electrode. A mixture paste was prepared. Next, the prepared positive electrode material mixture paste was applied to both surfaces of a positive electrode current collector made of aluminum foil except for the connecting portion of the positive electrode tab, and dried to form a positive electrode material mixture layer. The positive electrode precursor thus prepared was compressed to obtain a positive electrode. A positive electrode tab was also joined to the central portion of the positive electrode.

(Preparation of negative electrode)
Graphite was used as the negative electrode active material. A negative electrode active material 100 (weight ratio), polyvinylidene fluoride 1.0 (weight ratio) as a binder, carboxymethyl cellulose 1.0 (weight ratio) as a thickening agent, and an appropriate amount of water are mixed together. The mixture was stirred with an arm kneader to obtain a negative electrode paste. The negative electrode mixture paste was applied to both surfaces of a negative electrode current collector made of copper foil except for the connecting portion of the negative electrode tab, and dried to form a negative electrode mixture layer. The negative electrode precursor thus produced was compressed to obtain a negative electrode. Also, the negative electrode tab was joined to the end of the negative electrode on the winding end side.

(Fabrication of electrode body)
The positive electrode plate, the negative electrode plate, and the microporous membrane separator made of an olefin-based resin prepared as described above using a Φ4 winding core are wound by a winding machine, and an insulating film is attached to the terminal end on the winding end side. A cylindrical electrode assembly was produced by attaching the winding stop tape and then removing it from the winding core.

(Preparation of non-aqueous electrolyte)
1.0 M (mol/liter) of LiPF ₆ as an electrolyte salt dissolved in a non-aqueous solvent in which ethylene carbonate and dimethyl carbonate are mixed at a volume ratio of 40:60 (converted to 1 atm and 25° C.). was used as a non-aqueous electrolyte.

(Production of Cylindrical Battery)
The electrode group was inserted into an outer can having a height of 74.5 mm and a diameter of 22 mm, and the diameter of the opening was reduced (22 mm→21 mm). Next, the upper insulating plate 18 was inserted into the outer can. After that, an insulating resin (gasket) is placed in the opening of the outer can, the sealing body is placed on top of it, the non-aqueous electrolyte (electrolytic solution) is injected, and the sealing body, gasket, and outer can opening are pressed by a press machine. was crimped to produce a cylindrical battery. The rated capacity of the cylindrical battery was set to 5.0 Ah.

[Cylindrical battery of Example 2]
A cylindrical battery of Example 2, which was different from that of Example 1 only in the upper insulating plate, was used. In Example 2, an upper insulating plate 118 is used, the plan view of which is seen from below in the axial direction is shown in FIG. 3A, and the cross-sectional view along the line BB of FIG. 3A is shown in FIG. 3B. The upper insulating plate 118 was produced as follows. Specifically, a disc-shaped insulator made of phenolic resin (GP) mixed with glass fiber and having an outer diameter of 20 mm and a thickness of 0.3 mm was placed at a position 2 mm inward from the outer periphery of the insulating plate with a width of 0.1 mm and a depth of 0. An annular first groove (notch) 161 of 0.15 mm was provided. In addition, a plurality of radial second grooves (notches) 162 with a width of 0.1 mm and a depth of 0.1 mm extending from the center of the insulator toward the annular first groove 161 were formed in the disk-shaped insulator. . The first groove 161 and the second groove 162 are made to communicate. The disk-shaped insulator is further provided with first through holes 155 identical to the first through holes 55 described above, and a plurality of second through holes 156 identical to the plurality of second through holes 56 described above. established.

[Cylindrical battery of Example 3]
A cylindrical battery of Example 3, which was different from that of Example 1 only in the upper insulating plate, was used. In Example 3, an upper insulating plate 218 is used, the plan view of which is seen from below in the axial direction is shown in FIG. 4A, and the cross-sectional view taken along line CC of FIG. 4A is shown in FIG. 4B. The upper insulating plate 218 was produced as follows. Specifically, a disc-shaped insulator made of phenolic resin (GP) mixed with glass fiber and having an outer diameter of 20 mm and a thickness of 0.3 mm was placed at a position 2 mm inward from the outer periphery of the insulating plate with a width of 0.1 mm and a depth of 0. An annular first groove (notch) 261 of .2 mm was provided. In addition, a plurality of radial second grooves (notches) 262 with a width of 0.1 mm and a depth of 0.1 mm extending from the center of the insulator toward the annular first groove 261 are provided in the disk-shaped insulator. . The first groove 261 and the second groove 262 were not communicated. The disk-shaped insulator is further provided with first through holes 255 identical to the first through holes 55 described above, and a plurality of second through holes 256 identical to the plurality of second through holes 56 described above. established.

[Cylindrical battery of Example 4]
A cylindrical battery of Example 4, which was different from that of Example 1 only in the upper insulating plate, was used. In Example 4, an upper insulating plate 318 is used, the plan view of which is seen from below in the axial direction is shown in FIG. 5A, and the cross-sectional view taken along line DD of FIG. 5A is shown in FIG. 5B. The upper insulating plate 318 was produced as follows. Specifically, a disc-shaped insulator made of phenolic resin (GP) mixed with glass fiber and having an outer diameter of 20 mm and a thickness of 0.3 mm was placed at a position 1 mm inward from the outer periphery of the insulating plate with a width of 0.1 mm and a depth of 0. An annular first groove (notch) 361 of .2 mm was provided. In addition, a plurality of radial second grooves (cutouts) 362 with a width of 0.1 mm and a depth of 0.1 mm extending from the center of the insulator toward the annular first groove 361 are provided in the disk-shaped insulator. . The first groove 361 and the second groove 362 are made to communicate. The disk-shaped insulator is further provided with first through holes 355 identical to the first through holes 55 described above, and a plurality of second through holes 356 identical to the plurality of second through holes 56 described above. established.

[Cylindrical battery of Example 5]
A cylindrical battery of Example 5, which was different from Example 1 only in the upper insulating plate, was used. In Example 5, an upper insulating plate 418 is used, the plan view of which is seen from below in the axial direction is shown in FIG. 6A, and the cross-sectional view along the line EE of FIG. 6A is shown in FIG. 6B. The upper insulating plate 418 was produced as follows. Specifically, a disc-shaped insulator made of phenolic resin (GP) mixed with glass fibers and having an outer diameter of 20 mm and a thickness of 0.3 mm was placed at a position 3 mm inward from the outer periphery of the insulating plate with a width of 0.1 mm and a depth of 0. A 0.2 mm annular first groove (notch) 461 was provided. In addition, a plurality of radial second grooves (notches) 462 with a width of 0.1 mm and a depth of 0.1 mm extending from the center of the insulator toward the annular first groove 461 are provided in the disk-shaped insulator. . The first groove 461 and the second groove 462 are made to communicate. The disk-shaped insulator is further provided with first through holes 455 identical to the first through holes 55 described above, and a plurality of second through holes 456 identical to the plurality of second through holes 56 described above. established.

[Cylindrical battery of Comparative Example 1]
A cylindrical battery of Comparative Example 1 was a cylindrical battery that was different from Example 1 only in the upper insulating plate. In Comparative Example 1, an upper insulating plate 518 was used, the plan view of which is seen from below in the axial direction is shown in FIG. 7A, and the cross-sectional view taken along line FF of FIG. 7A is shown in FIG. 7B. The upper insulating plate 518 was produced as follows. Specifically, a disc-shaped insulator made of phenolic resin (GP) mixed with glass fiber and having an outer diameter of 20 mm and a thickness of 0.3 mm was placed at a position 2 mm inward from the outer periphery of the insulating plate with a width of 0.1 mm and a depth of 0. A .2 mm annular groove (notch) 561 was provided. Further, the disk-shaped insulator is provided with first through holes 555 identical to the first through holes 55 described above, and a plurality of second through holes 556 identical to the plurality of second through holes 56 described above are provided. established.

[Cylindrical battery of Comparative Example 2]
A cylindrical battery of Comparative Example 2 was a cylindrical battery that was different from Example 1 only in the upper insulating plate. In Comparative Example 2, an upper insulating plate 618 was used, the plan view of which is seen from below in the axial direction is shown in FIG. 8A, and the cross-sectional view along the line GG of FIG. 7A is shown in FIG. 8B. The upper insulating plate 618 was produced as follows. Specifically, a disk-shaped insulator having an outer diameter of 20 mm and a thickness of 0.3 mm made of phenolic resin (GP) mixed with glass fiber is provided with a width of 0.1 mm extending radially outward from the center of the insulator, A plurality of radial grooves (notches) 662 with a depth of 0.1 mm were provided. Further, the disk-shaped insulator is provided with first through holes 655 identical to the first through holes 55 described above, and a plurality of second through holes 656 identical to the plurality of second through holes 56 described above. established.

[Cylindrical battery of Comparative Example 3]
A cylindrical battery of Comparative Example 3 was a cylindrical battery that was different from Example 1 only in the upper insulating plate. In Comparative Example 3, an upper insulating plate 718 was used, the plan view of which is seen from below in the axial direction is shown in FIG. 9A, and the cross-sectional view taken along line HH of FIG. 9A is shown in FIG. 9B. The upper insulating plate 718 was produced as follows. Specifically, a disk-shaped insulator having an outer diameter of 20 mm and a thickness of 0.3 mm made of phenolic resin (GP) mixed with glass fiber is provided with a first through hole 755 identical to the first through hole 55 described above. , a plurality of second through holes 756 identical to the plurality of second through holes 56 described above are provided.

[Electrolyte Penetration Test]
After the electrolyte was injected, the liquid level was checked, and the electrolyte permeation time, which was the time required for the liquid level to fall below the upper insulating plate, was measured.

[Plate crush test]
Discharge (CC): 0.2 CA x 2.5 V was performed before the flat plate crushing test.
The crushing was performed by sandwiching the cylindrical battery between two flat plates arranged substantially parallel to each other and compressing the cylindrical battery. The crushing is performed by compressing the cylindrical battery by 10% until its diameter is reduced by 10% deformation crushing (crushing in which the compression distance between two flat plates is 10% of the diameter of the cylindrical battery before deformation). was compressed until its diameter was reduced by 25%.
A crushing speed of 15 mm/sec was adopted.
25° C. was adopted as the test temperature.
For each cylindrical battery, 5 samples were tested 5 times.
The test was evaluated by confirming the presence or absence of short-circuit traces due to cracks in the upper insulating plate on the upper part of the electrode body after the test.

[Combustion test]
Before the combustion test, (CCCV): 0.3 CA x 4.20 V, 0.05 CA cut was performed.
The distance between the cylindrical battery and the tip of the gas burner was set at 38 mm.
By heating the side surface of the cylindrical battery with a gas burner, the cylindrical battery was forced to generate abnormal heat and burn.
For each cylindrical battery, 5 samples were tested 5 times.
Those in which the exhaust valve operated after heating and did not explode were evaluated as OK, and those in which the exhaust valve operated but the battery exploded were evaluated as NG.
In addition, those in which no pinholes were present on the side surface of the battery after the test were evaluated as OK, and those in which pinholes were present on the side surface of the battery after the test were evaluated as NG.

[Test results]
Table 1 shows the test results.

As shown in Table 1, in the cylindrical battery of Comparative Example 2 in which the upper insulating plate was not provided with the annular groove, short-circuit marks were generated in two of the five samples in the 25% crush test. Also, in the cylindrical battery of Comparative Example 3, in which the upper insulating plate was not provided with the annular groove, short-circuit marks were generated in 3 out of 5 samples in the 25% crushing test. On the other hand, in the cylindrical batteries of Examples 1 to 5 using the upper insulating plate provided with the annular first groove, no trace of short-circuit could be confirmed in any of the 10% crush and 25% crush tests. Therefore, by providing the annular first groove in the upper insulating plate, it is possible to control how the upper insulating plate cracks, and to greatly suppress or prevent the electrode body from being damaged by fragments of the upper insulating plate.

Further, as shown in Table 1, using an upper insulating plate provided with only one of the first groove and the second groove, or using an upper insulating plate without providing both the first groove and the second groove, In the cylindrical batteries of Comparative Examples 1 to 3, the electrolyte permeation time was 90 minutes or more, and the electrolyte could not be quickly filled into the body.

On the other hand, in the cylindrical batteries of Examples 1 to 5 using the upper insulating plate provided with both the first groove and the second groove, the electrolyte permeation time could be shortened to 85 minutes or less, and especially the first groove In the cylindrical batteries of Examples 1, 2, 4, and 5 in which the second groove was communicated with the second groove, the electrolyte permeation time could be significantly shortened to 80 minutes or less. Therefore, by providing an annular first groove and a plurality of second grooves extending substantially radially outward from the radially inner side to the first groove side in the upper insulating plate, the electrolyte is distributed evenly to the electrode body. and can be quickly impregnated. Further, by connecting the annular first groove and the radial second groove, the electrode body can be impregnated with the electrolyte more uniformly and quickly.

In the combustion test, in Comparative Examples 1 and 3, some samples had pinholes on the side surface of the battery. This is because, in the cylindrical batteries of Comparative Examples 1 and 3, the upper insulating plate does not have a plurality of second grooves extending substantially radially outward. It is presumed that the exhaust valve did not operate smoothly because the passage was insufficient. In contrast, the cylindrical batteries of Examples 1 to 5 and Comparative Example 2, in which the upper insulating plate was provided with a plurality of second grooves extending substantially radially outward, prevented the generation of pinholes in the combustion test. I was able to

It should be noted that the present disclosure is not limited to the above embodiments and modifications thereof, and various improvements and modifications are possible within the scope of the claims of the present application and their equivalents.

For example, in the above-described embodiment, the annular first groove 61 has a shape in which the width in the radial direction gradually decreases toward the upper side in the axial direction, and the tip of the first groove 61 in the upper side in the axial direction is sharp. The case of having However, the annular first groove may have any shape on a plane including the radial direction and the axial direction, for example, it may have a rectangular shape or a semicircular shape. You may

Also, in the above example, the upper insulating plate was made of phenolic resin mixed with glass fiber, but the upper insulating plate may be made of any material. For example, the top insulating plate may be made of acrylic, phenolic, polycarbonate, polypropylene, polyethylene, polyphenyl carbonate, or the like. However, if the upper insulating plate is made of a hard insulating material such as phenolic resin mixed with glass fiber, acrylic, or phenol, the upper insulating plate will melt and the gas will be exhausted when the cylindrical battery overheats. It is preferable to be able to effectively suppress or prevent clogging of the passage.

In addition, when the outer diameter in the radial direction of the sealing portion 41 that accommodates the sealing member 17 in the outer can 16 is smaller than the outer diameter in the radial direction of the body portion 42 that accommodates the electrode body 14 in the outer can 16 explained. However, the outer diameter in the radial direction of the sealing portion of the outer can that accommodates the sealing member may be the same as the outer diameter in the radial direction of the body portion of the outer can that accommodates the electrode body. It can be big.

Also, as shown in FIG. 2A, the case where the first through-hole 55 for inserting the positive electrode lead 20 has a semicircular opening has been described. Also, the case where the first through hole 55 exists in one side region when the upper insulating plate 18 is divided into two by a plane including the diameter of the outer edge 59 and the thickness direction (axial direction) has been described. However, the layout of the first through holes for inserting the positive electrode lead in the upper insulating plate is not limited to the layout shown in FIG. 2A, and any layout may be used. For example, the first through hole for inserting the positive electrode lead may be provided in the radially central portion of the upper insulating plate. Then, a plurality of identical second grooves may radially extend radially at equal or non-equal intervals in the circumferential direction.

10 cylindrical battery, 11 positive electrode, 12 negative electrode, 13 separator, 14 electrode body, 16 outer can, 17 sealing body, 18, 118, 218, 318, 418 upper insulating plate, 20 positive electrode lead, 21 negative electrode lead, 23 terminal plate 24 Exhaust valve 25 Insulating member 26 Sealing plate 27 Gasket 30 Bottomed cylindrical part 34 Groove part 41 Sealing part 42 Body part 60

Groove

61, 161, 261, 361, 461 First Groove, 62, 162, 262, 362, 462 Second groove, 68 Bottom.

Claims

a cylindrical outer can with a bottom;
a wound electrode body housed in the outer can;
a sealing body that closes the opening of the outer can;
an insulating plate disposed in the outer can and positioned between the sealing body and the electrode body in the axial direction;
The insulating plate has an annular first groove and a plurality of second grooves extending substantially radially outward from a radially inner side toward the first grooved side in an end face on the electrode body side in the axial direction. and a cylindrical battery.
The radial outer diameter of the sealing portion of the outer can containing the sealing body is smaller than the radial outer diameter of the body portion of the outer can containing the electrode body. 2. Cylindrical battery according to 1.
The cylindrical battery according to claim 1 or 2, wherein the second groove communicates with the first groove.
A lead electrically connecting the electrode body and the sealing body,
The insulating plate has a lead insertion hole through which the lead is inserted,
4. Any one of claims 1 to 3, wherein the opening area of the lead insertion hole is 1/3 or more of the area of the region surrounded by the outer edge of the insulating plate in a plan view when viewed from the axial direction. 2. Cylindrical battery according to item 1.