WO2016121319A1

WO2016121319A1 - Cylindrical nonaqueous electrolyte secondary battery

Info

Publication number: WO2016121319A1
Application number: PCT/JP2016/000213
Authority: WO
Inventors: 雄史山上; 心原口; 森　敏彦
Original assignee: 三洋電機株式会社
Priority date: 2015-01-30
Filing date: 2016-01-18
Publication date: 2016-08-04
Also published as: JP2018049680A

Abstract

A cylindrical nonaqueous electrolyte secondary battery which has a configuration wherein a sealing body that seals an opening of a case main body is provided with a valve element, and which is suppressed in increase of the battery temperature by enhancing the exhaust ventilation performance from the bottom. A cylindrical nonaqueous electrolyte secondary battery (10) comprises: a bottomed cylindrical case main body (12) which has an opening at one end and contains an electrode body (30); a sealing body (20) which has an upper valve element (24) and a lower valve element (26) and seals the opening at one end of the case main body (12); and an insulating plate (40) which is arranged between the electrode body (30) and the sealing body (20). The electrode body (30) has a wound structure which is obtained by winding up a positive electrode plate and a negative electrode plate, with a separator being interposed therebetween. A bottom (12b) at the other end of the case main body (12) comprises a valve part (12d) and a thin part (13) that continuously or discontinuously surrounds the valve part (12d). The insulating plate (40) has a first opening (40a) and a second opening (40b), and covers at least a part of one end of a hollow part (36) that is formed at the inner end of the winding direction of the electrode body (30).

Description

Cylindrical non-aqueous electrolyte secondary battery

The present disclosure relates to a cylindrical nonaqueous electrolyte secondary battery.

In Patent Document 1, a thin wall portion (bottom marking) is provided at the bottom of a battery case, and when the gas pressure rises to a predetermined value or more due to abnormal heating or the like, the thin wall portion is broken, and the bottom exhaust port generated by the breakage The structure which discharges | emits gas from is described. Thereby, even when the pressure in the battery suddenly increases, it is said that cracks can be suppressed in the cylindrical part of the battery case.

Patent Document 2 describes that an upper end opening of a case body of a battery case is sealed with a sealing body. Patent Document 2 also describes that an opening is provided in each of the sealing body side bottom plate and the upper insulating plate constituting the sealing body, and gas generated in the battery case is exhausted. The upper insulating plate is disposed between the sealing body and the electrode body inside the case body. A valve body is disposed on the upper side of the sealing body side bottom plate. The valve body is broken when the lower gas pressure is increased, and a gas passage is formed.

International Publication No. 2014/045569 International Publication No. 2014/064882

As the capacity of the battery increases, the temperature of the gas in the battery case rises due to heat generated by an internal short circuit and the internal pressure tends to increase. In order to suppress such an increase in gas pressure, a battery case is formed by combining the bottom marking described in Patent Document 1 and the opening of the upper insulating plate and the valve body of the sealing body described in Patent Document 2. It is conceivable that gas is discharged from the lower part and the upper part.

On the other hand, in both cases of Patent Documents 1 and 2, the upper end of the hollow portion formed at the inner end in the winding direction of the electrode body is opened through the opening of the upper insulating plate. Accordingly, the hollow portion functions as an exhaust passage through which the gas generated in the electrode body is discharged. In this case, the gas tends to be discharged from the upper part of the battery, but the pressure in the hollow part is lowered inside the battery and the force to break the thin part at the bottom cannot be obtained, and the exhaust from the bottom may not occur. In addition, even if the thin portion at the bottom is broken, the amount of gas discharged from the bottom may be reduced. As a result, the balance between the exhaust from the top and bottom of the battery is deteriorated, and the effect of cooling the battery by exhaust cannot be sufficiently obtained, and the temperature may rise inside the battery. When the battery temperature rises, the battery case may thermally expand.

The purpose of the cylindrical non-aqueous electrolyte secondary battery according to an embodiment of the present disclosure is to have a structure in which a valve body is disposed in a sealing body that seals an opening of a case body, and the exhaust performance from the bottom is increased, thereby It is to suppress the temperature rise.

A cylindrical non-aqueous electrolyte secondary battery according to an embodiment of the present disclosure includes a bottomed cylindrical case body having an opening at one end and accommodating an electrode body, and a valve body and sealing the one end opening of the case body. A sealing body, and an insulating plate disposed between the electrode body and the sealing body, and the electrode body has a winding structure formed by winding a positive electrode plate and a negative electrode plate with a separator interposed therebetween. The bottom of the other end of the case body has a valve portion and a thin portion that continuously or discontinuously surrounds the valve portion, the insulating plate has an opening, and the winding of the electrode body It covers at least a part of one end of the hollow portion formed at the inner end in the direction.

According to the cylindrical non-aqueous electrolyte secondary battery according to an embodiment of the present disclosure, the internal pressure of the battery increases due to heat generated by an internal short circuit or the like in a configuration in which a valve body is disposed in a sealing body that seals the opening of the case body. In this case, by suppressing the exhaust from the upper part of the battery and increasing the exhaustability from the bottom part, it is possible to improve the balance of the exhaust and suppress an increase in the battery temperature.

It is sectional drawing of the cylindrical nonaqueous electrolyte secondary battery which is an example of embodiment. It is a bottom view of the cylindrical nonaqueous electrolyte secondary battery shown in FIG. It is a figure corresponding to Drawing 2 which shows another example of a thin part. It is the perspective view which looked at the sealing body side baseplate which comprises the cylindrical nonaqueous electrolyte secondary battery shown in FIG. 1 from the lower side. It is the figure which looked at the upper insulating board which comprises the cylindrical nonaqueous electrolyte secondary battery shown in FIG. 1 from upper direction. It is sectional drawing of the cylindrical nonaqueous electrolyte secondary battery of another example of embodiment. It is the perspective view which looked at the sealing body side bottom board which comprises the cylindrical nonaqueous electrolyte secondary battery shown in FIG. 6 from the lower side. It is the figure which looked at the upper insulating plate which comprises the cylindrical nonaqueous electrolyte secondary battery of Experimental example 1 from upper direction. It is the figure which looked at the upper insulating plate which comprises the cylindrical nonaqueous electrolyte secondary battery of another example of embodiment from the upper direction. It is the figure which looked at the upper insulating plate which comprises the cylindrical nonaqueous electrolyte secondary battery of another example of embodiment from the upper direction. It is the figure which looked at the upper insulating plate which comprises the cylindrical nonaqueous electrolyte secondary battery of another example of embodiment from the upper direction.

Hereinafter, an example of the embodiment will be described in detail with reference to the drawings. The drawings referred to in the embodiments are schematically described, and the dimensional ratios of the components drawn in the drawings are appropriately changed. Specific dimensional ratios and the like should be determined in consideration of the following description. For convenience of explanation, “upper and lower” are used as terms indicating directions, the sealing body side is referred to as “upper”, and the bottom side of the case body is referred to as “lower”.

FIG. 1 is a cross-sectional view of a cylindrical nonaqueous electrolyte secondary battery 10 which is an example of an embodiment. The cylindrical nonaqueous electrolyte secondary battery 10 includes a battery case 11, an electrode body 30 accommodated in the battery case 11, and an electrolyte (not shown). Hereinafter, the cylindrical nonaqueous electrolyte secondary battery 10 is simply referred to as a secondary battery 10.

The battery case 11 includes a case main body 12 which is a bottomed cylindrical metal container, and a sealing body 20 which closes one end (upper end in FIG. 1) of the case main body 12. The inside of the battery case 11 is sealed by the case body 12 and the sealing body 20.

The case main body 12 has an annular convex portion 15 formed by pressing one end side portion (upper portion in FIG. 1) of the cylindrical portion 12a from the outside to the inside through press working. In the case body 12, the sealing body 20 is placed on the upper surface of the convex portion 15. As long as the convex part 15 can support the sealing body 20 on the upper surface, the convex part 15 may be formed by extruding a plurality of circumferential positions of the cylindrical part 12a from the outside to the inside.

The sealing body 20 includes a sealing body side bottom plate 22 and an upper valve body 24 and a lower valve body 26 disposed on the upper side of the sealing body side bottom plate 22. The sealing body side bottom plate 22 has a bottom plate opening 22a described later. Each of the upper valve body 24 and the lower valve body 26 is broken when the pressure on the lower side increases as described later, and a gas discharge hole is formed. Thereby, the sealing body 20 functions as an upper safety valve.

The case body 12 is formed in a cylindrical shape having a bottom 12b by subjecting a metal plate (metal plate) containing iron as a main component to press working including drawing. For example, the case body 12 is formed by pressing a bottomed cylinder from a nickel-plated steel plate obtained by applying nickel plating to a steel plate. The case body 12 may be formed of a simple steel plate that does not have nickel plating.

A valve portion 12d and a thin portion 13 are formed on the bottom 12b of the case body 12. The thin portion 13 is broken when the battery internal pressure reaches a predetermined pressure, so that the valve portion 12d is released (opened) to form a gas exhaust port in the bottom portion 12b. Thereby, the bottom 12b functions as a lower safety valve. The bottom 12b and the sealing body 20 will be described later.

The electrode body 30 has a winding structure in which a positive electrode plate 31 and a negative electrode plate 32 are wound via a separator 33. Specifically, the electrode body 30 is formed by winding a positive electrode plate 31 and a negative electrode plate 32 in a spiral shape with a separator 33 interposed between the positive electrode plate 31 and the negative electrode plate 32. A columnar hollow portion 36 is formed at the inner end of the electrode body 30 in the winding direction by winding the separator 33. When the upper end of the separator 33 is not inclined and extends in the vertical direction, the diameter of the upper end of the hollow portion 36 is substantially the same as the diameter of the center in the vertical direction of the hollow portion 36, but as shown in FIG. The diameter surrounded by the inclined upper end may be smaller than the diameter of the center of the hollow portion 36 in the vertical direction.

A positive electrode lead 34 is attached to the positive electrode plate 31, and a negative electrode lead 35 is attached to the negative electrode plate 32. The secondary battery 10 includes an upper insulating plate 40 disposed between the electrode body 30 and the sealing body 20, more specifically, between the electrode body 30 and the convex portion 15. In addition, the secondary battery 10 includes a lower insulating plate 41 disposed between the electrode body 30 and the bottom portion 12 b of the case body 12.

In the example shown in FIG. 1, the positive electrode lead 34 extends to the sealing body 20 side through the first opening 40 a of the upper insulating plate 40, and the negative electrode lead 35 passes through the outside of the lower insulating plate 41 to the bottom 12 b of the case body 12. Extends to the side. The upper insulating plate 40 will be described later.

The secondary battery 10 has, for example, a volume energy density of 700 Wh / L or more. In a battery having such a high energy density, in the conventional configuration, as described later, the exhaust balance from the upper and lower sides of the battery deteriorates, so that the temperature easily rises, and the risk of burning off in the module environment increases. In the embodiment, in such a battery having a high energy density, a structure in which a hollow portion formed at the center portion of the electrode body 30 is covered by the upper insulating plate 40 as described later is employed to suppress exhaust from the sealing body 20 side. By doing so, the exhaust from the bottom 12b side is improved, and the rise in battery temperature can be reduced.

Also, as will be described in detail later, in the secondary battery 10, a lithium-containing transition metal oxide is used as the positive electrode active material, and a material capable of inserting and extracting lithium ions is used as the negative electrode active material. Further, a non-aqueous electrolyte is used as the electrolyte.

[Positive electrode]
The positive electrode plate 31 is composed of, for example, a positive electrode current collector and a positive electrode mixture layer formed on the positive electrode current collector. As the positive electrode current collector, a metal foil that is stable within the potential range of the positive electrode plate 31 such as aluminum, or a film in which this metal is disposed on the surface layer can be used. The positive electrode mixture layer includes a positive electrode active material. The positive electrode mixture layer preferably includes a conductive material and a binder in addition to the positive electrode active material. The positive electrode plate 31 is formed by, for example, applying a positive electrode mixture slurry containing a positive electrode active material and a binder on a positive electrode current collector, drying the coating film, and rolling the positive electrode mixture layer on both surfaces of the current collector. Can be produced.

Specific examples of the lithium-containing transition metal oxide used for the positive electrode active material include a general formula Li _a Ni _x M _1-x O ₂ (0.9 ≦ a ≦ 1.2, 0.8 ≦ x <1, M is A composite oxide represented by at least one element selected from the group consisting of Co, Mn, and Al). Among complex oxides, Ni—Co—Mn lithium-containing transition metal complex oxides are preferable because they are excellent in regenerative characteristics in addition to output characteristics. Ni—Co—Al-based lithium-containing transition metal composite oxides are more preferred because of their high capacity and excellent output characteristics.

In the positive electrode mixture layer containing a conductive material, the conductive material is used to increase the electrical conductivity of the positive electrode mixture layer. Examples of the conductive material include carbon materials such as carbon black, acetylene black, ketjen black, and graphite. These may be used alone or in combination of two or more.

In the positive electrode mixture layer including the binder, the binder maintains a good contact state between the positive electrode active material and the conductive material, and increases the binding property of the positive electrode active material and the like to the surface of the positive electrode current collector. Used for. Examples of the binder include fluorine resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. Further, these resins, carboxymethyl cellulose (CMC) or a salt thereof (CMC-Na, CMC-K, CMC-NH ₄ or the like, may be a partially neutralized salt), polyethylene oxide (PEO), etc. May be used in combination. These may be used alone or in combination of two or more.

[Negative electrode]
The negative electrode plate 32 includes a negative electrode current collector and a negative electrode mixture layer formed on the negative electrode current collector. As the negative electrode current collector, a metal foil that is stable in the potential range of the negative electrode plate 32 such as copper, a film in which this metal is disposed on the surface layer, or the like can be used. The negative electrode mixture layer includes a negative electrode active material. The negative electrode mixture layer preferably includes a binder in addition to the negative electrode active material. The negative electrode plate 32 is formed by, for example, applying a negative electrode mixture slurry containing a negative electrode active material and a binder on a negative electrode current collector, drying the coating film, and rolling the negative electrode mixture layer on both sides of the current collector. Can be produced.

As the negative electrode active material, a carbon material capable of inserting and removing lithium ions can be used. The carbon material is preferably particles containing graphite. The negative electrode active material preferably includes one or both of a negative electrode active material of silicon and a silicon compound and a negative electrode active material that is a carbon material. The silicon compound is preferably silicon oxide particles represented by SiO _x (0.5 ≦ x ≦ 1.5). Further, the silicon compound is more preferably coated with a material containing carbon to contain a carbon film. The carbon coating is preferably composed mainly of amorphous carbon. By using amorphous carbon, it is possible to form a good and uniform film on the surface of the silicon compound, and it is possible to further promote the diffusion of lithium ions into the silicon compound. The mass ratio of the carbon material to the silicon compound is preferably 99: 1 to 70:30, and more preferably 97: 3 to 90:10.

In the negative electrode mixture layer containing the binder, the binder can be a fluorine resin, PAN, polyimide resin, acrylic resin, polyolefin resin, or the like, as in the case of the positive electrode. When preparing a negative electrode mixture slurry using an aqueous solvent, styrene-butadiene rubber (SBR), CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof (PAA-Na, PAA-K, etc.) It is preferable to use polyvinyl alcohol (PVA) or the like.

[Separator]
As the separator 33, a porous sheet having ion permeability and insulating properties is used. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. As a material of the separator 33, olefin-based resins such as polyethylene and polypropylene, cellulose, and the like are preferable. The separator 33 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin resin.

Further, from the viewpoint of suppressing deterioration of the separator 33 due to heat generation of the positive electrode plate 31 during discharge under high temperature conditions, a heat resistant layer containing a heat resistant material is formed on the surface of the separator 33 facing the positive electrode plate 31. More preferably. For example, the heat-resistant layer is composed of a resin having excellent heat resistance such as engineer plastic or an inorganic compound such as ceramics. As specific examples of the resin constituting the heat-resistant layer, polyamide resins such as aliphatic polyamide and aromatic polyamide (aramid), polyimide resins such as polyamideimide and polyimide are more preferable. In addition, inorganic particles may be used for the heat-resistant layer, and examples of the inorganic particles include metal oxides and metal hydroxides. Of these, alumina, titania and boehmite are more preferable, and alumina and boehmite are more preferable. In addition, you may use 2 or more types of inorganic particles for a heat resistant layer. When a short-circuit occurs, heat is generated by a short-circuit current flowing, but having a heat-resistant layer improves heat resistance and is advantageous because it can reduce melting of the separator 33 due to heat. is there.

[Electrolytes]
The electrolyte is a nonaqueous electrolyte containing, for example, a nonaqueous solvent and an electrolyte salt dissolved in a nonaqueous solvent. The non-aqueous electrolyte is not limited to a non-aqueous electrolyte that is a liquid electrolyte, and may be a solid electrolyte using a gel polymer or the like.

As the non-aqueous solvent, for example, a chain carbonate or a cyclic carbonate is used. Examples of the chain carbonate include diethyl carbonate (DEC), methyl ethyl carbonate (MEC), and dimethyl carbonate (DMC). Examples of the cyclic carbonate include propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC). In particular, it is preferable to use a mixed solvent of a chain carbonate and a cyclic carbonate as a non-aqueous solvent having a low viscosity, a low melting point, and a high lithium ion conductivity. Moreover, fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC) can also be used.

Also, for the purpose of improving the output, compounds containing esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and γ-butyrolactone can be added to the above solvent. Moreover, fluorinated chain carboxylic acid esters such as fluorinated chain carbonic acid ester and methyl fluoropropionate (FMP) can also be used.

In addition, compounds containing a sulfone group such as propane sultone for the purpose of improving cycleability; 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 1,3-dioxane, 1,4-dioxane, 2-methyl A compound containing an ether such as tetrahydrofuran can be added to the solvent.

Also includes nitriles such as butyronitrile, valeronitrile, n-heptanenitrile, succinonitrile, glutaronitrile, adiponitrile, pimeonitrile, 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, etc. A compound, a compound containing an amide such as dimethylformamide, and the like can also be added to the solvent. A solvent in which a part of these hydrogen atoms (H) is substituted with fluorine atoms (F) can also be used.

The electrolyte salt dissolved in the non-aqueous solvent is preferably a lithium salt. Examples of the lithium _{_{salt, LiBF 4, LiClO 4, LiPF}} 6, LiAsF 6, LiSbF 6, LiAlCl 4, LiSCN, LiCF 3 SO 3, LiC (C 2 F 5 SO 2), LiCF 3 CO 2, Li (P (C ₂ O ₄ ) F ₄ ), Li (P (C ₂ O ₄ ) F ₂ ), LiPF _6-x (C _n F _{2n + 1} ) _x (1 <x <6, n is 1 or 2), LiB ₁₀ Cl ₁₀ , LiCl, LiBr, LiI, chloroborane lithium, lower aliphatic lithium carboxylate, Li ₂ B ₄ O ₇ , Li (B (C ₂ O ₄ ) ₂ ) [lithium-bisoxalate borate (LiBOB) ], Borates such as Li (B (C ₂ O ₄ ) F ₂ ), LiN (FSO ₂ ) ₂ , LiN (C ₁ F _{2l + 1} SO ₂ ) (C _m F _{2m + 1} SO ₂ ) {l , M is an integer greater than or equal to 1} and the like. These lithium salts may be used alone or in combination of two or more. Among these, it is preferable to use at least a fluorine-containing lithium salt from the viewpoints of ion conductivity, electrochemical stability, and the like, and for example, LiPF ₆ is preferably used. The concentration of the lithium salt is preferably 0.8 to 1.8 mol per liter of the nonaqueous solvent.

Hereinafter, the configurations of the bottom 12b of the case body 12, the sealing body 20, and the upper insulating plate 40 will be described in detail with reference to FIGS. 2 to 5 as appropriate.

[Bottom of the case body]
FIG. 2 is a bottom view of the secondary battery 10 shown in FIG. The bottom portion 12b of the case body 12 is formed in a disc shape, and includes a disc-shaped valve portion 12d disposed in the center portion, and an annular thin portion 13 that continuously surrounds the periphery of the valve portion 12d. In FIG. 2, the thin portion 13 is indicated by sand. Specifically, the thin portion 13 is formed in a perfect circle shape centered on the center O of the bottom portion 12b in the bottom view. By providing the annular thin portion 13, a marking portion 14 that is a concave portion that forms a planned opening portion is formed. The bottom part 12b consists of the thin part 13 and the part remove | deviated from the thin part 13, ie, the main-body parts 12c other than the thin part 13, and the thickness of the thin part 13 is smaller than the thickness of the main-body part 12c. The valve portion 12 d is an inner portion of the thin portion 13. The thin-walled portion 13 is broken when the gas pressure inside the battery case 11 increases, and discharges the gas inside.

Thus, a portion corresponding to the valve portion 12d surrounded by the thin portion 13 of the bottom portion 12b is opened when the internal pressure reaches a predetermined pressure to form a gas exhaust port. For this reason, the valve portion 12d is a planned opening portion when the internal pressure is increased, and functions as a lower safety valve.

The ratio of the thickness of the thin portion 13 to the thickness t of the bottom portion 12b is preferably 0.15 or less in consideration of durability during normal use and operability of the safety valve when the internal pressure is increased.

The ratio of the area of the valve part 12d to the entire area when the bottom part 12b of the case body 12 is viewed from below is preferably 0.07 to 0.55, more preferably 0.14 to 0.45. preferable. The area of the valve portion 12d is, for example, 15 mm ² to 150 mm ² .

FIG. 3 shows two other examples of the thin portion 13. Another example of the thin-walled portion 13 shown in FIG. 3A forms a part of a ring centered on the center O of the bottom portion 12b. That is, the thin portion 13 is formed in a C-shape that is arcuate. And the inside of the thin part 13 becomes the valve part 12d. For this reason, the inner peripheral side and the outer peripheral side of the thin wall portion 13 are connected by the connecting portion 16 having a large thickness. As a result, the thin portion 13 discontinuously surrounds the disc-shaped valve portion 12d. In the case of the thin-walled portion 13 in FIG. 3 (a), a gas exhaust port that breaks and discharges the gas inside the battery case 11 to the outside when the internal gas pressure increases, as in the thin-walled portion 13 in FIG. Form. *

3B, two other examples of the thin wall portion 13 are formed on both sides of the center O of the bottom portion 12b. Each thin portion 13 has an annular shape composed of an arc and a straight line connecting both ends of the arc. The two thin portions 13 have a symmetrical shape with respect to the center O. An inner portion of the thin portion 13 is a valve portion 12d. In addition, the shape of the thin part 13 is not limited to the shape shown in FIG. 2, FIG. For example, the thin portion 13 is not limited to an annular shape, and may be a polygon having a straight line such as a rectangle.

[Sealing body]
Returning to FIG. 1, the sealing body 20 is attached to the opening of the case body 12 via the gasket 42, thereby ensuring the hermeticity inside the battery case 11. The convex portion 15 supports the sealing body 20 via the gasket 42.

The sealing body 20 includes a cap 21 that is a top plate, a sealing body-side bottom plate 22, and a current interruption mechanism (CID mechanism). The current interruption mechanism is constituted by an upper valve body 24, an insulating member 25, and a lower valve body 26. The current interrupting mechanism is disposed between the cap 21 and the sealing body side bottom plate 22 to form a current path that electrically connects the upper valve body 24 and the lower valve body 26. And a current interruption mechanism interrupts | blocks a current path so that it may mention later, when the gas pressure in the battery case 11 increases.

The cap 21, the sealing body side bottom plate 22, the upper valve body 24, and the lower valve body 26 constituting the sealing body 20 are made of metal and have a disc shape or a ring shape. For example, the cap 21 has a disk shape having a cylindrical portion whose upper end is closed, and an outward flange 21a is formed at the lower end over the entire circumference. A cap opening 21b is formed at one of the upper end portions of the cap 21 or at a plurality of positions in the circumferential direction.

FIG. 4 is a perspective view of the sealing body side bottom plate 22 as viewed from below. At least a part of the sealing body side bottom plate 22 is separated from the lower valve body 26. Specifically, the sealing body side bottom plate 22 has a tapered cylindrical portion 22b inclined with respect to the axial direction (vertical direction in FIG. 4), and has a shape in which the lower end is closed by the disc portion 22c. The sealing body side bottom plate 22 is formed with an outward flange 22d on the entire upper end. Bottom plate openings 22a are formed at a plurality of circumferential positions (three positions in the illustrated example) of the disk portion 22c. Further, the sum of the opening areas of the plurality of bottom plate openings 22 a is smaller than the sum of the opening areas of the cap openings 21 b of the cap 21.

Referring back to FIG. 1, a cap 21 is disposed at the upper end of the sealing body 20, and a sealing body side bottom plate 22 is disposed at the lower end. Accordingly, the sealing body side bottom plate 22 is disposed to face the upper side of the upper insulating plate 40 described later. Between the flange 21a of the cap 21 and the flange 22d of the sealing body side bottom plate 22, the outer peripheries of the upper valve body 24, the insulating member 25, and the lower valve body 26 are sandwiched in order from the upper side to the lower side. The upper valve body 24 is formed in a disc shape. The lower valve body 26 is also formed in a disc shape and is disposed below the upper valve body 24. A convex portion 26 a that protrudes upward is formed at the central portion of the lower valve body 26, and contacts the central portion of the lower surface of the upper valve body 24. The convex portion 26 a of the lower valve body 26 is preferably joined to the central portion of the lower surface of the upper valve body 24 by welding. The

flanges

21a and 22d of the cap 21 and the sealing body side bottom plate 22, the upper valve body 24, the insulating member 25, and the outer periphery of the lower valve body 26 are not joined. The outer peripheral portions of the

flanges

21 a and 22 d, the upper valve body 24, the insulating member 25, and the lower valve body 26 are sandwiched in the vertical direction by the inner peripheral portion of the gasket 42 held by the upper end portion of the case body 12. Thereby, the convex part which consists of the cylinder part 22b and the disc part 22c of the sealing body side baseplate 22 is spaced apart from the lower valve body 26. As shown in FIG.

The thickness of each

valve body

24, 26 is sufficiently smaller than the thickness of the case body 12. In the lower valve body 26 and the upper valve body 24, a thin portion (not shown) is formed on the convex portion 26a of the lower valve body 26 or a portion outside the contact portion with the convex portion 26a. The shape of the thin part of each

valve body

24 and 26 is formed in C shape which is cyclic | annular or circular arc shape. The insulating member 25 is formed in an annular shape and is sandwiched between the outer peripheries of the upper valve body 24 and the lower valve body 26. Thereby, the cap 21 is electrically connected to the sealing body side bottom plate 22 through the current interrupting mechanism.

The positive electrode lead 34 is connected to the lower surface of the sealing body side bottom plate 22 by welding. As a result, the cap 21 is connected to the positive electrode plate 31 and becomes a positive electrode terminal. On the other hand, the negative electrode lead 35 is connected to the inner surface of the bottom 12b of the case body 12 by welding. As a result, the case main body 12 is connected to the negative electrode plate 32 and becomes a negative electrode terminal.

The upper valve body 24 and the lower valve body 26 seal the lower space S1 of the sealing body side bottom plate 22 from the outside of the battery case 11. In the upper valve body 24 and the lower valve body 26, when the internal gas pressure rises due to heat generation due to an internal short circuit, the thin portions of the upper valve body 24 and the lower valve body 26 break. Gas passages (not shown) are formed in the upper valve body 24 and the lower valve body 26, respectively. As a result, the gas inside the battery case 11 is discharged. The gas generated inside the battery due to the breakage of the upper valve body 24 is discharged to the outside through the cap opening 21b. Thus, the current interrupt mechanism has the function of an upper safety valve that discharges high-pressure gas. In addition, the cap 21 may employ a configuration in which the cap opening 21b is not formed and the cap 21 is broken by an increase in pressure on the lower side.

Further, after the thin portion of the lower valve body 26 is broken, the gas pressure in the space S2 formed between the upper valve body 24 and the lower valve body 26 is increased before the thin portion of the upper valve body 24 is broken. By doing so, the upper valve body 24 swells to the cap 21 side. Then, the upper valve body 24 and the lower valve body 26 are separated by a contact portion of the convex portion 26a, for example, a joint portion. Accordingly, the current path that electrically connects the upper valve body 24 and the lower valve body 26 is blocked, and the current path that electrically connects the positive electrode plate 31 and the cap 21 is also blocked. The current cut-off mechanism cuts off a current path connecting the upper valve body 24 and the lower valve body 26 when the gas pressure in the space S3 between the upper valve body 24 and the lower valve body 26 is equal to or higher than a predetermined cut-off pressure. For this reason, excellent safety can be ensured.

It should be noted that the upper valve body 24 and the lower valve body 26 may not be formed with a thin portion, but may be configured such that a gas passage is formed by partially breaking due to an increase in the lower gas pressure. Throughout the present specification, the “valve element” means a member in which a gas passage leading to the other side (upper side in FIG. 1) is formed due to breakage caused by an increase in gas pressure on one side (lower side in FIG. 1).

[Upper insulating plate]
The upper insulating plate 40 is disposed between the convex portion 15 and the electrode body 30 for the purpose of preventing contact between the convex portion 15 of the case body 12 and the electrode body 30. The upper insulating plate 40 is composed mainly of, for example, glass fiber reinforced phenol resin. By using a glass fiber reinforced phenol resin as a main component, an insulating plate having high strength and high heat resistance can be obtained. The upper space S1 of the upper insulating plate 40 communicates with the lower space S2 of the lower valve body 26 through the bottom plate opening 22a of the sealing body side bottom plate 22.

There is a close relationship between the shape of the upper insulating plate 40 and the gas exhaust from the upper part of the battery case 11 by the sealing body 20. FIG. 5 is a view of the upper insulating plate 40 as viewed from above. The upper insulating plate 40 is disc-shaped and is arranged side by side in the circumferential direction on the substantially semicircular first opening 40a formed on one side (lower side in FIG. 5) and on the other side (upper side in FIG. 5). Three second openings 40b. Each of the second openings 40b is substantially the same shape and is formed in an arc shape centered on the central axis O. The first opening 40 a and each second opening 40 b are provided for passing gas generated in the power generation element including the electrode body 30. In a state where the upper insulating plate 40 is disposed between the convex portion 15 of the case body 12 and the electrode body 30, the first opening 40 a passes the positive electrode lead 34 (FIG. 1) from the lower side to the upper side. In the vicinity of the central axis O on the other side (the upper side in FIG. 1) of the first opening 40a, an overhanging portion 40c that projects inward is formed. And the overhang | projection part 40c has covered the whole upper end of FIG. 1 which is one end of the hollow part 36 formed in the center vicinity of the electrode body 30. FIG. In FIG. 5, the upper end of the hollow portion 36 is indicated by a portion with an X attached to a circle.

The upper insulating plate 40 may contain, for example, a reinforcing material other than fiber such as silica, clay, mica, or a resin having high heat resistance other than phenol resin (for example, epoxy resin, polyimide resin, etc.). As fibers contained in the upper insulating plate 40, boron fibers, aramid fibers, or the like may be used in addition to glass fibers.

Further, the lower insulating plate 41 is formed in a disk shape having openings at a part or a plurality of positions by the same material as the material forming the upper insulating plate 40. For example, as shown in FIG. 1, the lower insulating plate 41 has a lower opening 41 a in the center including the position facing the lower end of the hollow portion 36.

The opening ratio, which is the ratio of the sum of the upper end opening areas of the

openings

40a and 40b to the entire outer area of the upper surface of the upper insulating plate 40, is preferably 20% or more and 50% or less. When the aperture ratio is in the above range, the liquid injection property of the electrolytic solution is not impaired, and the upper insulating plate 40 has sufficient strength.

According to the secondary battery 10 described above, when the internal pressure rises due to heat generation due to an internal short circuit or the like as described above, the gas is discharged to the outside through the sealing body 20. Then, before or after the gas is discharged from the sealing body 20 side, or at the same time, the valve portion 12d of the bottom portion 12b of the case body 12 is opened, and the gas is discharged also from the bottom portion 12b side.

The gas exhaust is generated during the thermal runaway of the battery, and the exhaust from the sealing body 20 side is the electrode body 30, the

openings

40a and 40b of the upper insulating plate 40, the bottom plate opening 22a, the lower valve body 26, and the upper valve body. 24 gas passages and the cap opening 21b. At this time, the upper insulating plate 40 arranged below the gas passage of the upper valve body 24 plays a role of suppressing exhaust from the sealing body 20 to the outside.

This improves the balance of exhaust from the top and bottom of the battery, so that the rise in battery temperature can be suppressed. In particular, when the energy density of the secondary battery 10 is high, for example, when the volume energy density is 700 Wh / L or more, the internal pressure due to temperature rise tends to increase. On the other hand, when the upper end of the hollow portion is not covered with the upper insulating plate as in the configuration described in Patent Document 2, the amount of exhaust from the sealing body 20 increases, and the bottom 12b, which is the main exhaust path, increases. May interfere with exhaust.

In the embodiment, the upper insulating plate 40 covers the upper end of the hollow portion 36 of the electrode body 30, thereby suppressing the exhaust from the sealing body 20, and the pressure of the hollow portion 36 is increased by the upper insulating plate 40. As a result, the bottom 12b of the case body 12 can be more positively broken, and a gas exhaust port is easily formed. For this reason, the amount of gas exhaust from the gas exhaust port increases. When the gas exhaust is performed from the sealing body 20 side and the bottom 12b side, the flow resistance on the sealing body 20 side is larger than the flow resistance on the bottom 12b side, so the amount of exhaust from the bottom 12b is high. Thereby, the balance of exhaust from the sealing body 20 side and the bottom portion 12b side can be improved, and an increase in temperature in the entire battery can be suppressed. For this reason, since the temperature at the time of a thermal runaway of a battery can be reduced, when using many batteries side by side as a module, possibility that a temperature rise will be transmitted with a plurality of batteries can be lowered.

FIG. 6 is a cross-sectional view of a secondary battery 10 according to another example of the embodiment. FIG. 7 is a perspective view of the sealing body side bottom plate 22 constituting the secondary battery 10 as viewed from below. In this example, the bottom plate opening 22a is formed in the sealing body side bottom plate 22 at a plurality of circumferential positions (three positions in the illustrated example) in contact with the lower surface of the lower valve body 26.

In such a configuration, the gas whose temperature has increased from the electrode body 30 is sent from the

openings

40a and 40b of the upper insulating plate 40 to the bottom plate opening 22a. Then, the gas flows into a wide space S <b> 2 between the center portion of the lower valve body 26 and the sealing body side bottom plate 22 through a gap between the flange 22 d of the sealing body side bottom plate 22 and the peripheral portion of the lower valve body 26. The

valve bodies

24 and 26 are broken by the pressure increase in the space S2, a gas passage is formed, and the internal gas is discharged.

According to the above configuration, the exhaust amount from the sealing body 20 can be further suppressed. Accordingly, a gas discharge port is easily formed in the bottom portion 12b of the case body 12 during the thermal runaway of the battery. For this reason, the temperature rise of a battery can be suppressed more effectively.

In the above configuration, when exhausted from the sealing body 20, the sum of the opening areas of the plurality of bottom plate openings 22 a tends to be the smallest in the cross-sectional area of the sealing body-side exhaust path. For this reason, the opening area of the plurality of bottom plate openings 22 a greatly affects the exhaust amount from the sealing body 20. The total opening area of the plurality of bottom plate openings 22a is, for example, 15 mm ² or less, and is preferably 10 mm ² or less, more preferably 5 mm ² or less from the viewpoint of improving the exhaust performance of the battery as a whole and suppressing an increase in battery temperature. Particularly preferably, the thickness is 0.5 mm ² to 2 mm ² .

[Experimental example]
Hereinafter, the present disclosure will be further described with experimental examples, but the present disclosure is not limited to these experimental examples.

<Experimental example 1>
[Production of positive electrode]
100 parts by mass of lithium nickel cobalt aluminum composite oxide represented by LiNi _0.91 Co _0.06 Al _0.03 O ₂ as a positive electrode active material, 1 part by mass of acetylene black (AB) as a conductive agent, and polyfluoride as a binder. After mixing 1 part by mass of vinylidene chloride (PVdF) and adding an appropriate amount of N-methyl-2-pyrrolidone (NMP), a positive electrode mixture slurry was prepared. Next, the positive electrode mixture slurry was applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 13 μm and dried. This is cut into a predetermined electrode size and rolled using a roller so that the positive electrode mixture density is 3.6 g / cc, and a positive electrode plate 31 having a positive electrode mixture layer formed on both sides of the positive electrode current collector is obtained. Produced.

[Production of negative electrode]
93 parts by weight of graphite powder as a negative electrode active material, 7 parts by weight of silicon oxide SiO, 1 part by weight of carboxymethyl cellulose (CMC) as a thickener, and styrene-butadiene rubber (SBR) as a binder After mixing 1 part by mass and adding an appropriate amount of water, a negative electrode mixture slurry was prepared. Next, the negative electrode mixture slurry was applied to both sides of a negative electrode current collector made of a copper foil having a thickness of 6 μm and dried. This was cut into a predetermined electrode size and rolled using a roller so that the composite material density was 1.65 g / cc to produce a negative electrode in which a negative electrode composite layer was formed on both surfaces of the negative electrode current collector.

[Preparation of non-aqueous electrolyte]
Ethylene carbonate (EC), dimethyl carbonate (DMC), and methyl ethyl carbonate (MEC) were mixed at a volume ratio of 20: 75: 5. Furthermore, LiPF ₆ was dissolved to a concentration of 1.4 mol / L with respect to the mixed solvent to prepare a nonaqueous electrolytic solution.

[Production of battery]
A positive electrode lead 34 made of aluminum was attached to the positive electrode plate 31, and a negative electrode lead 35 made of nickel was attached to the negative electrode plate 32. Then, the positive electrode plate 31 and the negative electrode plate 32 were spirally wound through the separator 33 to produce a wound electrode body 30. As the separator 33, a polyethylene microporous membrane coated with a heat-resistant layer in which polyamide and alumina fillers are dispersed is used. The electrode body 30 was accommodated in the case body 12 having an outer diameter of 18.2 mm and a height of 65 mm, and the non-aqueous electrolyte was injected. The thin part 13 was formed in the bottom part 12b of the case body 12 by forming an annular (perfectly circular) marking part 14 from the outside in advance. In addition, an upper insulating plate 40 and a lower insulating plate 41 are disposed above and below the electrode body 30. And after injection | pouring of nonaqueous electrolyte, the opening part of the case main body 12 was sealed with the gasket 42 and the sealing body 20, and the secondary battery 10 with a volume energy density of 739 Wh / L was produced by 18650 type | mold.

The sealing body 20 has the structure shown in FIG. 1 and FIG. 6, and three bottom plate openings 22 a are formed in the peripheral edge portion in contact with the lower valve body 26 in the sealing body side bottom plate 22. As shown in FIG. 8, the upper insulating plate 40 is provided with a plurality of

openings

40a and 40b. Unlike the example of FIG. 5, the insulating plate of FIG. 8 is not formed with an overhanging portion that covers the portion of the circular body in FIG. 8 that is the upper end of the hollow portion 36 of the electrode body 30. Thus, in the example of FIG. 8, the upper end of the hollow portion 36 faces the first opening 40 a and is not covered with the insulating plate 40.

<Experimental example 2>
Similar to the example shown in FIGS. 6 and 7, the upper end of the hollow portion 36 of the electrode body 30 was covered with the upper insulating plate 40, and a battery was fabricated in the same manner as in Experimental Example 1 except that.

<Experimental example 3>
1, 2, 4, and 5, in the sealing body side bottom plate 22, the bottom plate opening 22 a is formed in the disc portion 22 c that is not in contact with the lower valve body 26, and the other examples are experimental examples. A battery was produced in the same manner as in 2.

For each battery of Experimental Examples 1 to 3, the battery temperature after firing and the operability of the bottom marking were evaluated in the heating and firing test by the following method. The evaluation results for each battery are shown in Table 1.

[Heating ignition test]
The batteries of Experimental Examples 1 to 3 were evaluated according to the following procedure.
(1) Under an environment of 25 ° C., the battery is charged with a constant current of 0.3 C (1050 mA) until the battery voltage becomes 4.2 V, and then the current value becomes 0.02 C (70 mA) with a constant voltage. Continued charging.
(2) A thermocouple was welded to the side of the battery charged in (1), and the battery was put into a tubular furnace having a diameter of 50 mm heated to 700 ° C. In addition, when putting a battery into a tubular furnace, it is desirable to perform an experiment using a jig so that the battery does not directly contact the furnace, and the battery is introduced to the center of the tubular furnace in a high temperature state.
(3) The temperature of the battery side surface during battery heating is measured, and heating is performed until the battery runs out of heat due to heating. After battery ignition, the battery was removed from the tubular furnace and the appearance of the battery after the test was observed.

Table 1 shows the results of evaluating the maximum battery temperature when the heating and ignition test was performed for the batteries of Experimental Example 1 and Experimental Example 2. For the battery maximum temperature, two tests were conducted in each of Experimental Examples 1 and 2, and the average value of the maximum temperatures in each test is shown in Table 1.

From Table 1, when the upper end of the hollow portion 36 of the electrode body 30 was covered with the upper insulating plate 40, the maximum temperature was about 70 ° C. lower than that of the experimental example 1 that was not covered. From this, in the shape of the upper insulating plate 40 of Experimental Example 1, it is considered that the exhaust amount from the sealing body 20 is increased because the hollow portion 36 that is a gas discharge path is located directly below the sealing body-side bottom plate 22. It is done. As a result, it is considered that the balance between the exhaust from the upper part of the battery and the exhaust from the bottom 12b is deteriorated.

Also, the operating rate of the bottom 12b in the heating and ignition test of each battery in Experimental Example 2 and Experimental Example 3 was obtained and compared. In the comparison of the operating rates, five tests were performed in each of Experimental Example 2 and Experimental Example 3, and the ratio at which the bottom portion 12b was broken at the thin-walled portion 13 was obtained and compared as the stamping operating rate.

From Table 2, in Experimental Example 2 in which the bottom plate opening 22a is closed in contact with the lower valve body 26, the bottom 12b is reliably broken at the thin portion 13 to form a gas exhaust port. On the other hand, in the experimental example 3 in which the bottom plate opening 22a is formed in the disc portion 22c and is not blocked by the peripheral portion of the lower valve body 26, the operating rate is as low as 60%. As described above, the reason why the operating rate is high in Experimental Example 2 is that the upper insulating plate 40 covers the hollow portion of the electrode body 30 and the bottom plate opening 22a is blocked by the lower valve body 26. It is possible that there is. Thereby, in Experimental Example 2, it is considered that the exhaust from the sealing body 20 at the time of battery ignition is remarkably reduced, and the gas pressure is rapidly applied to the bottom 12b.

In the embodiment, the shape of the upper insulating plate 40 is not limited to the shape shown in FIG. 5, and various shapes can be adopted. 9 to 11 are views of an upper insulating plate 40 constituting a secondary battery 10 of another example of the embodiment as viewed from above. In the example of FIG. 9, the upper insulating plate 40 includes a circular outer peripheral portion 40d and a substantially triangular inner portion 40e, and the top of the inner portion 40e is coupled to the inner peripheral surface of the circular outer peripheral portion 40d. Insulating plate openings 40f are formed at three positions between the circular outer peripheral portion 40d and the inner portion 40e.

In the example of FIG. 10, the upper insulating plate 40 includes a circular outer peripheral portion 40d and a disc-shaped inner portion 40g, and the inner portion 40g is connected to the circular outer peripheral portion 40d by radial legs 40h. Then, fan-shaped (arc-shaped) openings 40i are formed at three positions between the circular outer peripheral portion 40d and the inner portion 40g.

In the example of FIG. 11, semicircular openings 40j are formed at four positions at equal intervals in the circumferential direction of the upper insulating plate 40. A substantially square inner portion 40k is formed inside the four openings 40j. 9 to 11, the

inner portions

40e, 40g, and 40k cover the upper end of the hollow portion 36 of the electrode body 30 (the portion marked with a circle X). In each of the above examples, the case where the upper insulating plate 40 covers the entire upper end of the hollow portion 36 has been described. However, only a part of the hollow portion 36 may be covered by the upper insulating plate. However, it is preferable to cover the entire upper end of the hollow portion 36 with the upper insulating plate 40 in order to enhance the exhaustability from the bottom 12b of the case body 12 and suppress the rise in battery temperature.

DESCRIPTION OF SYMBOLS 10 Cylindrical nonaqueous electrolyte secondary battery (secondary battery), 11 Battery case, 12 Case main body, 12a Cylinder part, 12b Bottom part, 12c Main body part, 12d Valve part, 13 Thin part, 14 Marking part, 15 Convex part, 16 connection part, 20 sealing body, 21 cap, 21a flange, 21b cap opening, 22 sealing body side bottom plate, 22a bottom plate opening, 22b cylinder part, 22c disc part, 22d flange, 24 upper valve body, 25 insulating member, 26 lower Valve body, 26a
Convex part, 30 electrode body, 31 positive electrode plate, 32 negative electrode plate, 33 separator, 34 positive electrode lead, 35 negative electrode lead, 36 hollow part, 40 upper insulating plate, 40a first opening part, 40b second opening part, 40c Part, 40d circular outer peripheral part, 40e inner part, 40f opening part, 40g inner part, 40h leg part, 40i, 40j opening part, 40k inner part, 41 lower insulating plate, 41a lower opening part, 42 gasket.

Claims

A bottomed cylindrical case body having an opening at one end and accommodating the electrode body;
A sealing body having a valve body and sealing one end opening of the case body;
An insulating plate disposed between the electrode body and the sealing body,
The electrode body has a wound type structure formed by winding a positive electrode plate and a negative electrode plate with a separator interposed therebetween,
The bottom part of the other end of the case body has a valve part and a thin part surrounding the valve part continuously or discontinuously,
The said insulating plate has an opening part, The cylindrical non-aqueous electrolyte secondary battery which covers at least one part of the end of the hollow part formed in the winding direction inner end of the said electrode body.
The cylindrical non-aqueous electrolyte secondary battery according to claim 1, wherein the sealing body includes a sealing body-side bottom plate that has a bottom plate opening and is opposed to the upper side of the insulating plate.
The cylindrical non-aqueous electrolyte secondary battery according to claim 2, wherein the bottom plate opening is formed at a position in the sealing body side bottom plate in contact with the lower surface of the valve body.
The negative electrode plate has a negative electrode active material,
The negative electrode active material contains a carbon material and silicon or a silicon compound,
The cylindrical nonaqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein the volume energy density is 700 Wh / L or more.
The ratio of the total of the upper end opening area of the opening of the insulating plate to the entire outer area of the upper surface of the insulating plate is 20% to 50%, according to any one of claims 1 to 4. The cylindrical non-aqueous electrolyte secondary battery described.