WO2017090219A1

WO2017090219A1 - Cylindrical battery

Info

Publication number: WO2017090219A1
Application number: PCT/JP2016/004301
Authority: WO
Inventors: 大塚　正雄; 靖志中村; 亜希子岡部
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2015-11-27
Filing date: 2016-09-21
Publication date: 2017-06-01
Also published as: JP2019016423A

Abstract

This cylindrical battery is provided with: an electrode group obtained by rolling up a positive electrode, a negative electrode, and a first separator interposed therebetween, which all have a belt-like shape; an electrolyte; a bottomed cylindrical battery case; and an opening sealing plate. The negative electrode is provided with a negative electrode collector and negative electrode active material layers formed on both surfaces of the negative electrode collector. The negative electrode has a thin part provided at an area within a length L₃ from the outer end of the negative electrode; a tapered part adjacent to the thin part; and a body part other than these parts. The thickness of the negative electrode active material layer on the outer peripheral side of the tapered part is gradually reduced from the body part side toward the thin part side. The electrode group is formed such that the outer end of the positive electrode overlaps the tapered part via the first separator, and further includes a second separator interposed between the tapered part and the outer end of the positive electrode.

Description

Cylindrical battery

The present invention relates to a cylindrical battery provided with a wound electrode group.

In a cylindrical battery provided with a wound electrode group, it is easy to increase the capacity by winding the electrode. On the other hand, even if the electrode group is formed simply by winding the electrode, a step is formed at the end portion of the outermost periphery of the electrode (hereinafter also simply referred to as the outer end of the electrode), and the diameter of the electrode group is reduced at this portion. Since it becomes large, it becomes difficult to insert it into the battery case.

In Patent Document 1, in the wound electrode group of the cylindrical alkaline storage battery, a thin portion with a small thickness of the active material layer is formed in a region having a predetermined length from the outer end of the negative electrode. The positive electrode and the negative electrode are wound so that the outer end of the positive electrode overlaps.

In Patent Document 2, in the wound electrode group, a short circuit is suppressed by inserting a protective member that covers a ridge formed at the outer end of the positive electrode between the positive electrode and the separator.

JP 2005-56774 A JP 2005-56676 A

In the thin part of the negative electrode of Patent Document 1, the thickness of the negative electrode active material layer is small. Therefore, when the thin portion of the negative electrode and the outer end of the positive electrode are overlapped, the balance of the active material amount (N / P ratio balance) between the positive electrode active material layer and the negative electrode active material layer facing each other is near the outer end. Collapse and output and capacity are likely to decrease. Further, when the negative electrode region other than the thin wall portion and the outer end of the positive electrode are overlapped, the diameter of the electrode group becomes the largest at the outer end portion of the positive electrode, and it becomes difficult to insert into the battery case. Further, when an external force is applied to the case, the largest pressure is applied to the outer end portion of the positive electrode, and a short circuit is likely to occur.

In Patent Document 2, since the protective member is disposed between the positive electrode and the separator, when the electrode is tightly wound or the number of turns is increased from the viewpoint of increasing the capacity, the step of the protective member May cause a crack in the positive electrode and cause an internal short circuit.

An object of the present disclosure is to provide a cylindrical battery in which an electrode group can be easily inserted into a battery case, the occurrence of an internal short circuit is suppressed, and the N / P ratio balance in the vicinity of the outer end is suppressed. It is.

One aspect of the present disclosure includes a strip-shaped positive electrode, a strip-shaped negative electrode, an electrode group around which a strip-shaped first separator interposed between the positive electrode and the negative electrode is wound, an electrolyte, and an opening that accommodates the electrode group and the electrolyte A bottomed cylindrical battery case having a portion, and a sealing plate for sealing the opening,
The negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on both surfaces of the negative electrode current collector,
The negative electrode includes a thin portion provided in a region of length L ₃ from the outer end of the negative electrode, a tapered portion adjacent to the thin portion, and other body portions.
The thickness t _1o of the negative electrode active material layer on the outer peripheral side in the main body portion and the thickness t _3o of the negative electrode active material layer on the outer peripheral side in the thin portion satisfy t _1o > t _3o ,
The thickness t _2o of the negative electrode active material layer on the outer peripheral side of the taper portion is _{gradually decreased} from the main body portion side toward the thin wall portion side,
The electrode group is a cylinder, wherein the outer end of the positive electrode is disposed so as to overlap the tapered portion via the first separator, and further includes a second separator disposed between the outer end of the positive electrode and the tapered portion. The present invention relates to a battery.

According to the present disclosure, in the cylindrical battery, it is easy to insert the wound electrode group into the battery case, and the occurrence of an internal short circuit can be suppressed. In addition, the balance of the N / P ratio in the vicinity of the outer end of the positive electrode can be suppressed.

FIG. 1 is a cross-sectional view schematically showing a cylindrical battery according to an embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing the cylindrical battery of FIG. FIG. 3 is an enlarged view of a portion surrounded by a circle indicated by III in FIG. FIG. 4 is a schematic perspective view schematically showing an example of a negative electrode used in the electrode group of FIG. FIG. 5 is a schematic side view of the negative electrode of FIG. FIG. 6 is a schematic perspective view schematically showing another example of the negative electrode used in the electrode group in FIG. 2. FIG. 7 is a schematic side view of the negative electrode of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings as necessary.

[Cylindrical battery]
A cylindrical battery according to the present invention includes a strip-shaped positive electrode, a strip-shaped negative electrode, and an electrode group wound with a strip-shaped separator (first separator) interposed between the positive electrode and the negative electrode, an electrolyte, an electrode group, A bottomed cylindrical battery case having an opening for accommodating an electrolyte, and a sealing plate for sealing the opening. The negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on both surfaces of the negative electrode current collector. The negative electrode includes a thin portion provided in a region of the length L ₃ from the outer end of the negative electrode, and a tapered portion adjacent to the thin portion, and the other body portion. The thickness t _1o of the negative electrode active material layer on the outer peripheral side in the main body portion and the thickness t _3o of the negative electrode active material layer on the outer peripheral side in the thin portion satisfy t _1o > t _3o . The thickness t _2o of the negative electrode active material layer on the outer peripheral side of the taper portion is _{gradually decreased} from the main body portion side toward the thin portion portion side. The electrode group further includes a separator (second separator) disposed such that the outer end of the positive electrode overlaps the tapered portion via the first separator, and is disposed between the outer end of the positive electrode and the tapered portion. Including.

In the wound electrode group of the cylindrical battery, when the outer end (that is, the winding end) at the outermost periphery of the electrode is overlapped with the main body of the electrode, the diameter of the electrode group is the largest at this outer end, Hard to insert into the battery case. Since burr may exist at the outer end of the positive electrode, when an external force is applied to the battery case, if a large pressure is applied to the outer end portion of the positive electrode, the burr penetrates the separator, and a short circuit is likely to occur. Become. Further, when a large pressure is applied to the outer end portion of the positive electrode, a crack may occur in the outer end portion of the positive electrode, which may cause a short circuit. To reduce the overall diameter of the electrode group in order to facilitate insertion into the battery case and to prevent the occurrence of short circuits, the number of electrode turns can be reduced, the electrode thickness can be reduced, or the electrode group can be tightly wound. It is necessary to turn. Reducing the number of turns of the electrode or reducing the thickness is disadvantageous in terms of increasing the capacity, and if the electrode group is wound tightly, the internal resistance may increase or a short circuit may occur. When the electrode is wound around the thin portion formed at the outer end of the negative electrode so that the outer end of the positive electrode overlaps as in Patent Document 1, an increase in the diameter of the electrode group is suppressed. However, since the amount of the negative electrode active material in the thin-walled portion is small, the balance of the active material amount is lost between the thin-walled portion and the positive electrode facing the thin-walled portion, and the output and capacity are reduced.

In the cylindrical battery according to the present invention, as described above, the negative electrode on the outer peripheral side extends from the main body portion to the thin wall portion between the main body portion of the negative electrode and the thin wall portion formed in the region having a predetermined length from the outer end. A tapered portion where the thickness of the active material layer is reduced is formed, and the tapered portion is disposed so that the outer end of the positive electrode overlaps. With such a configuration, since the diameter of the electrode group measured at the position of the outer end of the positive electrode is suppressed from being excessively large, the electrode group can be easily inserted into the battery case. In addition, since the thickness of the negative electrode active material layer is larger in the tapered portion than in the thin portion, the quantitative balance (N / P ratio balance) between the negative electrode active material and the positive electrode active material in the vicinity of the outer end of the positive electrode may be lost. It is suppressed. Therefore, it is possible to suppress a decrease in capacity and output.

Furthermore, in the cylindrical battery according to the present invention, a second separator is disposed between the outer end of the positive electrode and the tapered portion. Thereby, it can suppress that an internal short circuit occurs in the outer end of a positive electrode, and its periphery, or internal resistance increases and it generates heat.

The thin-walled portion only needs to have a thickness of the negative electrode active material layer on the outer peripheral side that is at least smaller than that of the main body portion as described above. It may be smaller than the thickness of the inner peripheral side of the main body. In addition, the taper portion may be such that at least the thickness of the negative electrode active material layer on the outer peripheral side is gradually reduced from the main body portion side toward the thin wall portion side. In addition to the outer peripheral side, on the inner peripheral side, the thickness of the negative electrode active material layer of the taper portion may be gradually decreased from the main body portion side toward the thin wall portion side.

The length L ₃ of the thin portion, the length L ₁ of the main body portion described later, and the length L ₂ of the tapered portion are all determined based on the negative electrode active material layer on the outer peripheral side. That is, the thin-walled portion is a region where the thickness of the negative electrode active material layer on the outer peripheral side from the outer end (end surface on the outer peripheral side) of the negative electrode is t _3o , and the tapered portion is adjacent to the thin-walled portion and the negative electrode active material on the outer peripheral side. This is a region where the thickness of the material layer changes in an inclined manner.

The configuration of the cylindrical battery will be described below with reference to FIG. FIG. 1 is a cross-sectional view schematically showing the structure of a cylindrical battery according to an embodiment of the present invention. The cylindrical battery includes a bottomed cylindrical battery case 4 that also serves as a negative electrode terminal, an electrode group housed in the battery case 4, and an electrolyte (not shown). In the electrode group, a strip-shaped negative electrode 1, a strip-shaped positive electrode 2, and a strip-shaped separator (first separator) 3 interposed therebetween are spirally wound. A sealing plate 7 including a safety valve 6 is disposed in the opening of the battery case 4 via an insulating gasket 8, and the cylindrical battery is sealed by caulking the opening end of the battery case 4 inward. . The sealing plate 7 also serves as a positive electrode terminal, and is electrically connected to the positive electrode 2 via the positive electrode current collector plate 9.

In such a cylindrical battery, the electrode group is accommodated in the battery case 4, the electrolyte is injected, the sealing plate 7 is disposed in the opening of the battery case 4 via the insulating gasket 8, and the battery case 4 The opening end can be obtained by caulking and sealing. At this time, the negative electrode 1 of the electrode group is preferably electrically connected by contacting the battery case 4 on the outermost periphery.

The cylindrical battery is not particularly limited, and may be a primary battery or a secondary battery. Since an increase in resistance due to the occurrence of an internal short circuit or a crack in the positive electrode can be suppressed, the cylindrical battery is suitable as a secondary battery that repeats charging and discharging. Cylindrical batteries are particularly suitable for alkaline storage batteries such as nickel metal hydride storage batteries. The alkaline storage battery includes a nickel cadmium storage battery and a nickel zinc storage battery in addition to the nickel metal hydride storage battery. In particular, nickel-metal hydride storage batteries use electrodes having a relatively large thickness compared to other secondary batteries, and thus problems such as ease of insertion of an electrode group into a battery case and occurrence of internal short-circuits are likely to become obvious. Therefore, the configuration of the cylindrical battery of the present invention in which the thin portion and the tapered portion are provided is particularly suitable for application to a nickel metal hydride storage battery. In addition, in the nickel metal hydride storage battery, oxygen gas is generated during overcharge, but by providing a negative electrode active material layer that does not face the positive electrode on the outer peripheral side of the thin portion, oxygen gas generated during overcharge can be absorbed. it can. From this point of view, it is advantageous to apply the configuration of the cylindrical battery of the present invention to a nickel metal hydride storage battery.

FIG. 2 is a cross-sectional view schematically showing the cylindrical battery of FIG. The present invention is characterized in the vicinity of the outer end of the positive electrode of the wound electrode group. FIG. 3 shows an enlarged view of the vicinity of the outer end of the positive electrode (that is, a portion surrounded by a circle indicated by III in FIG. 2). FIG. 4 is a schematic perspective view schematically showing an example of a negative electrode used in the electrode group of FIG. FIG. 5 is a schematic side view of the negative electrode of FIG.

In the electrode group shown in FIG. 2, the positive electrode 2 and the negative electrode 1 are wound via a separator (first separator) 3. The negative electrode 1 includes a main body portion 1a located on the inner peripheral side in the electrode group, a thin portion 1c formed on the outer end side, and a tapered portion 1b located between the main body portion 1a and the thin portion 1c. Thin portion 1c is an area of a length L ₃ from the outer end of the negative electrode 1, the taper portion 1b is a region of length L ₂ adjacent to the thin portion 1c. Body portion 1a, of the negative electrode 1, a region other than the thin portion 1c and the tapered portion 1b, has a length L _1. The outermost periphery of the positive electrode 2 is covered with a thin portion 1 c of the negative electrode 1 through the first separator 3, and the thin portion 1 c is in contact with the inner wall of the battery case 4.

The negative electrode 1 includes a strip-shaped negative electrode current collector 11 and a negative electrode active material layer 12 formed on the surface of the negative electrode current collector 11. The negative electrode active material layer 12 includes a negative electrode active material layer 12 a formed on the outer peripheral surface of the negative electrode current collector 11 and a negative electrode active material layer 12 b formed on the inner peripheral surface of the negative electrode current collector 11. Contains. The thickness t _3o of the negative electrode active material layer 12a of the outer peripheral side of the thin portion 1c of the negative electrode 1 is smaller than the thickness t _1o of the negative electrode active material layer 12a of the outer periphery of the main body 1a (t _1o> t _3o) . And thickness _t2o of the negative electrode active material layer 12a of the outer peripheral side of the taper part 1b is _{decreasing gradually} toward the thin part 1c from the main-body part 1a side.

In the present invention, the electrode group is arranged so that the outer end of the positive electrode 2 overlaps the tapered portion 1b with the first separator 3 interposed therebetween. And the 2nd separator 3a is distribute | arranged between the outer end of the positive electrode 2, and the taper part 1b. At this time, it is preferable to arrange the second separator 3 a so as to overlap the outer end of the positive electrode 2 so as to protect the outer end of the positive electrode 2. With such a configuration, in the present invention, the wound electrode group can be easily inserted into the battery case, the occurrence of an internal short circuit can be suppressed, and the balance of the N / P ratio in the vicinity of the outer end can be suppressed. can do. In the illustrated example, the second separator 3 a is disposed between the tapered portion 1 b and the first separator 3 in contact with the outer end of the positive electrode 2. The second separator 3a may be disposed so as to overlap at least the outer end of the positive electrode 2 and its periphery so as to support the outer end of the positive electrode 2.

FIG. 6 is a schematic perspective view schematically showing another example of the negative electrode used in the electrode group of FIG. FIG. 7 is a schematic side view of the negative electrode of FIG. In the illustrated example, the thickness of the negative electrode active material layer on the inner peripheral side is small in the thin-walled portion of the negative electrode, as in the negative electrode active material layer on the outer peripheral side, and the negative electrode active material layer on the inner peripheral side is also in the tapered portion. The thickness gradually decreases from the main body portion side toward the thin wall portion side. Other than these, the example is the same as the example of FIGS.

More specifically, the negative electrode 21 includes a main body portion 21a located on the inner peripheral side of the electrode group, a thin portion 21c formed on the outer end side, and a tapered portion 21b located therebetween. . The negative electrode 21 includes a strip-shaped negative electrode current collector 31 and a negative electrode active material layer 32 formed on the surface of the negative electrode current collector 31. The negative electrode active material layer 32 includes a negative electrode active material layer 32 a formed on the outer peripheral surface of the negative electrode current collector 31 and a negative electrode active material layer 32 b formed on the inner peripheral surface. In the main body portion 21a, the tapered portion 21b, and the thin portion 21c, the relationship of the thickness of the negative electrode active material layer 32a on the outer peripheral side is the same as in the examples of FIGS.

The thickness t _3i of the inner peripheral negative electrode active material layer 32b in the thin portion 21c of the negative electrode 21 is smaller than the thickness t _1i of the inner peripheral negative electrode active material layer 32b in the main body 21a (t _1i > t _3i ). Further, the thickness t _2i of the negative electrode active material layer 32b on the inner peripheral side in the taper portion 21b is _gradually reduced from the main body portion 21a side toward the thin portion 21c.

Hereinafter, the components of the cylindrical battery will be described more specifically.

(Negative electrode)
The negative electrode has a main body part, a taper part, and a thin part in which the thickness of the negative electrode active material layer on the outer peripheral side of the electrode group is different. In the thin portion, the thickness t _3o of the negative electrode active material layer on the outer peripheral side is smaller than the thickness t _1o of the negative electrode active material layer on the outer peripheral side of the main body portion. Therefore, it is advantageous to provide a thin portion in a region where the negative electrode active material layer on the outer peripheral side does not face the positive electrode because the amount of the negative electrode active material that is not used for the electrode reaction can be reduced and the volume required for it can be reduced. In addition, although the thickness t _3o is small, by forming a negative electrode active material layer that does not face the positive electrode in the thin wall portion, the nickel hydrogen storage battery can absorb oxygen gas generated during overcharge.

In each part, the thickness of the negative electrode active material layer on the inner peripheral side is not particularly limited and may be the same. For example, considering the balance with the amount of the positive electrode active material of the opposite positive electrode, the thickness may be varied as necessary. May be. When the thickness of the negative electrode active material layer on the inner peripheral side is the same in the main body portion, the tapered portion, and the thin portion, this thickness may be the same as t _1o , for example.

6 and 7, if necessary, the thickness of the negative electrode active material layer on the inner peripheral side may be changed similarly to the thickness of the negative electrode active material layer on the outer peripheral side. In the taper portion, the thickness gradient of the negative electrode active material layer is not necessarily the same between the outer peripheral side and the inner peripheral side, and may be different. The position where the thickness of the negative electrode active material layer on the inner peripheral side starts to decrease from the main body side toward the thin wall side is not necessarily between the main body portion and the tapered portion (that is, the thickness of the negative electrode active material layer on the outer peripheral side is the main body). It does not need to coincide with the position where the portion starts to decrease from the portion side toward the thin portion side, and may overlap with either the main body portion or the tapered portion. Similarly, the position at which the decrease in the thickness of the negative electrode active material layer on the inner peripheral side converges does not necessarily coincide with the end point of the tapered portion (between the tapered portion and the thin portion), and the tapered portion and the thin portion. It may overlap with any of the above.

From the viewpoint of reducing the amount of the negative electrode active material that is not used for the electrode reaction, it is preferable to form a thin portion on the outermost periphery of the negative electrode where the negative electrode active material layer on the outer peripheral side does not face the positive electrode. The length L ₃ of the thin portion is, for example, 50% or more and 115% or less, and preferably 70% or more and 110% or less, or 80% or more and 105% or less of the length of the outermost periphery of the negative electrode.

The main body part is a region that is located on the center side (or inner peripheral side) of the electrode group, and that both surfaces face the positive electrode, and are mainly responsible for electrode reactions. In this specification, for the sake of convenience, the entire region of the negative electrode on the center side excluding the thin-walled portion and the tapered portion on the outer peripheral side is referred to as a main body portion, but in the main body portion, the region that does not face the innermost positive electrode of the negative electrode Then, if necessary, the thickness of the negative electrode active material layer may be partially reduced.

The thicknesses t _1o and t _1i of the negative electrode active material layers on the outer peripheral side and the inner peripheral side in the main body can be determined in consideration of the type of the battery, the balance with the amount of the positive electrode active material in the positive electrode, and the like. Each of t _1o and t _1i is, for example, from 0.01 mm to 0.3 mm, or from 0.1 mm to 0.2 mm.

The difference (t _1o -t _3o ) between the thickness t _1o of the negative electrode active material layer and the thickness t _3o of the negative electrode active material layer is preferably 0.01 mm or more and 0.2 mm or less, or 0.02 mm or more and 0 It may be 1 mm or less. The thickness t _1i of the negative electrode active material layer, also the difference between the thickness t _3i of the negative electrode active material layer (t _1i -t _3i), can be selected from the same range as (t _1o -t _3o). When the thickness difference is in such a range, it is easy to give a gradient of the thickness of the negative electrode active material layer in the tapered portion, and it becomes easier to ensure the ease of inserting the electrode group into the battery case. Moreover, even if the second separator is provided, the periphery of the outer end of the positive electrode is not easily affected by the step due to the second separator.

In the taper portion, the thickness t _2o of the negative electrode active material layer on the outer peripheral side is _{gradually reduced} from the main body portion side toward the thin portion portion side. That is, the thickness t _2o varies in an inclined manner within a range of t _3o ≦ t _2o ≦ t _1o . Further, when the thickness t _2i of the negative electrode active material layer on the inner peripheral side is decreased from the main body portion side toward the thin wall portion side, the thickness t _2i may be changed in an inclined manner within the range of t _3i ≦ t _2i ≦ t _1i. Good.

When the length (L ₂ ) of the taper portion is short, the taper portion has a steep gradient, and stress is easily applied to the outer end of the positive electrode disposed in the taper portion and the periphery thereof. That is, it is preferable that the length L ₂ has a certain size. From this point of view, the length L ₂ of the tapered portion, the length of the outermost periphery of the negative electrode, longer is favored over 1/6, may be 1/5 or more or 1/4 or more. The length L ₂ of the tapered portion is preferably equal to or less than half of the length of the outermost periphery of the negative electrode.

In the electrode group, the positive electrode and the negative electrode may be arranged so that the outer end of the positive electrode overlaps at least the taper portion, but the position of the end surface of the outer end of the positive electrode is near the center in the length direction of the taper portion. It is preferable to arrange a positive electrode and a negative electrode in For example, the end face of the outer end of the positive electrode is located in a region of ± 0.2 × L ₂ (preferably a region of ± 0.1 × L ₂ ) across the center in the length direction of the taper portion. It is preferable to overlap the outer end of the positive electrode with the tapered portion.

In the present invention, since the stress applied to the outer end of the positive electrode can be reduced by the taper portion and the second separator, even if the number of turns of the negative electrode is increased or the thickness is increased, the outer end of the positive electrode and the periphery thereof are increased. Generation of internal short circuit can be suppressed. The number of turns of the negative electrode can be selected according to the size of the cylindrical battery. For example, when the outer diameter of the cylindrical battery is 6 mm or more and 24 mm or less, it can be 2 or more and 10 or less, and can be 3 or more and 6 or less. Also good.

The negative electrode includes a negative electrode current collector (core material) and a negative electrode active material layer formed on both surfaces of the negative electrode current collector. As the negative electrode current collector, a known material and / or current collector can be used depending on the type of battery. As the negative electrode current collector, for example, a porous substrate such as a punching metal or a lath body, or a non-porous substrate such as a metal foil may be used. As the negative electrode active material layer, a negative electrode active material layer containing a known component can be adopted depending on the type of battery. The negative electrode active material layer only needs to contain at least a negative electrode active material, and may be a negative electrode mixture layer including a negative electrode active material, a binder, a conductive agent, and / or a thickener. These components may be appropriately selected according to the type of battery.

The nickel hydride storage battery will be described as an example. Examples of the material of the negative electrode current collector include stainless steel, nickel, or an alloy thereof. Examples of the negative electrode active material include known hydrogen storage alloys such as A ₂ B ₇ type (or Ce ₂ Ni ₇ type), AB ₅ type (CaCu ₅ type or MmNi ₅ type (Mm represents Misch metal)), Those having a crystal structure such as AB ₃ type (or CeNi ₃ type) and / or AB ₂ type (MgCu ₂ type or the like) can be used without particular limitation.

As the binder, a resin material, for example, a rubber-like material such as styrene-butadiene copolymer rubber (SBR), a polyolefin resin, a fluororesin such as polyvinylidene fluoride, and / or an acrylic resin (including its Na ion crosslinked product) And the like. Examples of the thickener include carboxymethyl cellulose (CMC) and a salt thereof, polyvinyl alcohol, and / or polyethylene oxide. Examples of the conductive agent include carbon black, conductive fibers, and / or organic conductive materials.

The negative electrode may be formed, for example, by attaching a negative electrode active material to a negative electrode current collector. Moreover, you may form a negative electrode by apply | coating the negative mix containing the structural component of a negative mix layer to a negative electrode electrical power collector, compressing to a thickness direction, and drying at an appropriate stage if needed.

The thickness of the negative electrode (main body part) may be determined in consideration of the type of battery and the balance with the positive electrode, but is preferably 0.1 mm or more and 0.6 mm or less, for example.

(Positive electrode)
At the outer end of the positive electrode and the periphery thereof, the length of the region facing the tapered portion (the length from the end surface of the outer end of the positive electrode) is, for example, 1% to 15% of the length of the positive electrode. % Or more and 5% or less is preferable.

As the positive electrode, a known positive electrode is used according to the type of battery. The positive electrode only needs to contain at least a positive electrode active material, and may be one obtained by molding and sintering a positive electrode mixture containing a positive electrode active material. Alternatively, a positive electrode active material or a positive electrode mixture supported on a positive electrode current collector (core material) (for example, filled or coated) may be used. The positive electrode mixture may include a conductive agent, a binder, and / or a thickener in addition to the positive electrode active material. The positive electrode can be obtained by a known method.

As the positive electrode current collector, a current collector of a known material and / or form can be used depending on the type of battery. The positive electrode active material, the conductive agent, the binder, and the thickener may be appropriately selected according to the type of battery.

A nickel metal hydride storage battery will be described as an example. Examples of the positive electrode current collector include a nickel foam, and a porous substrate formed of nickel or a nickel alloy such as a sintered nickel plate. As the positive electrode active material, for example, nickel compounds such as nickel hydroxide and / or nickel oxyhydroxide are used. The conductive agent, binder and thickener may be appropriately selected from those exemplified for the negative electrode. Further, as the conductive agent, conductive cobalt oxide such as cobalt hydroxide and / or γ-type cobalt oxyhydroxide may be used.

(Separator)
As the first separator and the second separator, for example, a microporous film, a nonwoven fabric, or a laminate thereof can be used depending on the type of battery. The material of the microporous membrane or the nonwoven fabric may be appropriately selected from known materials according to the type of battery and the operating temperature of the battery. For example, a resin or inorganic fiber is used.

The nickel hydride storage battery will be described as an example. Examples of the resin include polyolefin resins such as polyethylene and polypropylene, fluorine resins, and / or polyamide resins. The separator may be subjected to hydrophilization treatment such as corona discharge treatment, plasma treatment, and / or sulfonation treatment as necessary.

The thickness of each separator can be appropriately selected from the range of 10 μm to 300 μm, for example, and may be 15 μm to 200 μm, for example.

The second separator may be disposed between the outer end of the positive electrode and the tapered portion of the negative electrode, or may be disposed between the outer end of the positive electrode and the first separator in contact with the tapered portion of the negative electrode. Further, the second separator may be disposed between the taper portion of the negative electrode and the first separator in contact with the outer end of the positive electrode. In this case, the step at the end of the second separator is relaxed by the first separator, and the effect of suppressing the occurrence of an internal short circuit at the outer end of the positive electrode and its periphery can be enhanced.

The length of the second separator, the L _2, for example, 200% or less than 50%, may be 100% or less than 80%. The second separator only needs to protect the outer end of the positive electrode and its periphery. Therefore, a sufficient effect can be obtained even if the length of the second separator is shorter than the length L ₂ of the tapered portion. In this case, the length of the second separator, the L _2, for example, less than 50% to 100%, and preferably less than 80% or more 100%.

Since the first separator has a function of electrically insulating the positive electrode and the negative electrode, the width of the second separator may be made smaller than the width of the positive electrode and / or the negative electrode. However, from the viewpoint of more effectively suppressing the occurrence of an internal short circuit at the outer end of the positive electrode and its periphery, the width of the second separator is preferably larger than the width of the positive electrode, and even larger than the width of the negative electrode. Good. Further, the width of the second separator may be approximately the same as the width of the first separator.

The length of the second separator is the length of the second separator in the direction parallel to the length direction of the electrode, and the width of the second separator is the second length in the direction perpendicular to the length direction of the electrode. The length of the separator.

(Electrolytes)
The electrolyte includes a solute and a solvent that dissolves the solute. As the solute and the solvent, known materials can be used depending on the type of battery. The concentration of the solute and the specific gravity of the electrolyte can also be selected as appropriate.

When the nickel metal hydride storage battery is described as an example, an alkaline electrolyte such as an aqueous solution containing an alkali is used as the electrolyte. Examples of the alkali include alkali metal hydroxides such as lithium hydroxide, potassium hydroxide, and / or sodium hydroxide. The specific gravity of the alkaline electrolyte is, for example, 1.03 or more and 1.55 or less.

As other components such as a battery case and a sealing plate, known components can be used depending on the type of the battery.

Hereinafter, the present invention will be specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.

Example 1
An AA cylindrical nickel-metal hydride storage battery having a capacity of 2500 mAh was manufactured by the following procedure.

(1) Production of negative electrode Hydrogen storage alloy powder (La _0.40 Ce _0.60 Ni _3.63 Co _0.76 Mn _0.42 Al _0.29 , average particle size = about 45 μm) 100 parts by mass of SBR 0.7 parts by mass as binder By adding 0.15 parts by mass of CMC as a sticking agent, 0.3 parts by mass of ketjen black as a conductive agent, 0.7 parts by mass of yttrium oxide as an oxidation inhibitor, and adding and mixing an appropriate amount of water A negative electrode mixture slurry was prepared. SBR was used in the form of an aqueous dispersion.

The obtained negative electrode mixture slurry was applied to both surfaces of an iron punching metal (thickness 60 μm, hole diameter 1 mm, hole area ratio 42%) having a nickel plating on the surface as a negative electrode current collector. At this time, the coating amount of the negative electrode mixture slurry was changed in the length direction of the negative electrode current collector so that the thicknesses of the negative electrode active material layers on both sides were different between the main body part, the tapered part, and the thin part. The coating film of the negative electrode mixture slurry was dried at 95 ° C. for 10 minutes, and then the negative electrode was formed by pressing the coating film together with the negative electrode current collector with a roller. The resulting body of the negative electrode was, it is formed in a region of length L ₁ = 104 mm from the lengthwise end portions of the negative electrode current collector, the thickness t _1o and t _1i of the negative electrode active material layer, respectively, It was 0.14 μm. The thin portion is formed in a region having a length L ₃ = 39 mm from the other end in the length direction of the negative electrode current collector, and the thicknesses t _3o and t _3i of the negative electrode active material layer are each 0.08 μm. there were. The taper portion was formed in a region between the main body portion and the thin portion, and the length L ₂ of the taper portion was 12 mm.

(2) Production of positive electrode A non-sintered nickel positive electrode was produced by the following procedure.

First, nickel hydroxide powder containing 2.5% by mass of zinc and 1.0% by mass of cobalt as a coprecipitation component was added to an aqueous cobalt sulfate solution. While stirring the resulting mixture, an aqueous sodium hydroxide solution (sodium hydroxide concentration: 1 mol / L) was gradually added dropwise to adjust the pH to 11, followed by further stirring for a predetermined time. The precipitate was filtered off from the resulting mixture. The precipitate separated by filtration was washed with water and vacuum-dried to obtain a powder in which the surface of nickel hydroxide particles was coated with 5% by mass of cobalt hydroxide.

10 parts by mass of an aqueous sodium hydroxide solution (sodium hydroxide concentration: 48% by mass) was added to 1 part by mass of the powder obtained above. The resulting mixture was heat-treated at 85 ° C. for 8 hours with stirring, then washed with water and dried at 65 ° C. By this heat treatment, in the layer containing cobalt hydroxide on the surface of the nickel hydroxide particles, a part of cobalt hydroxide is made higher-order and converted into cobalt oxyhydroxide, and sodium is introduced. Composite particles in which a coating layer containing cobalt oxyhydroxide and 1% by mass of sodium was formed on the surface of the nickel hydroxide particles were obtained.

By adding and mixing 25 parts by mass of an aqueous solution (CMC concentration: 0.2% by mass) containing CMC as a binder to 100 parts by mass of the obtained composite particles and zinc oxide mixed powder, A positive electrode mixture slurry was prepared. The mass ratio of the composite particles and zinc oxide in the mixed powder was 100: 2.

The obtained positive electrode mixture slurry was filled in pores of a nickel foam (surface density (unit weight) of about 325 g / m ² , thickness of about 1.2 mm) as a positive electrode current collector and dried. The dried product was rolled to a thickness of 0.66 mm to obtain a positive electrode (length 118 mm, width 44.7 mm, thickness 0.66 μm).

In addition, the exposed part of the positive electrode collector which does not hold | maintain an active material was provided in the one end part of the length direction of a positive electrode collector, and the positive electrode lead was connected to this exposed part.

(3) Production of Nickel Metal Hydride Battery Between the negative electrode obtained in (1) above and the positive electrode obtained in (2) above, the first separator (length 325 mm, width 46.7 mm, thickness 0.082 μm) The electrode group was prepared by winding these in a spiral shape. At this time, winding was performed so that the main body portion of the negative electrode was the inner peripheral side, the thin portion was the outer peripheral side, and the outer end of the positive electrode was overlapped with the tapered portion of the negative electrode. At this time, a second separator (length 10 mm, width 46.7 mm, thickness 0.082 μm) was disposed between the outer end of the positive electrode and the tapered portion, and between the tapered portion and the first separator. . The second separator was arranged so that the end face on the outer peripheral side of the positive electrode came near the center in the length direction. As the first separator and the second separator, a sulfonated polypropylene nonwoven fabric (thickness 82 μm, basis weight 50 g / m ² , and sulfonation degree 1.90 × 10 ⁻³ ) was used. The number of turns of the negative electrode in the electrode group was 6.

The obtained electrode group was inserted into an AA bottomed cylindrical metal battery case (outer diameter 14.60 mm) having a ring-shaped groove on the opening side, and the outermost negative electrode (thin wall portion) was inserted. The battery case was brought into contact with the inner surface. Moreover, the positive electrode lead connected to the positive electrode was welded to the inner bottom surface of the cover plate of the sealing body. The sealing body is arranged so as to close the gas vent hole at the center of the top plate of the lid plate having a circular vent hole at the center, the insulating packing attached to the periphery of the lid plate, and the lid plate. And a cap-like positive electrode terminal having a protrusion that covers the valve body.

Next, an alkaline electrolyte was poured into the battery case, the opening of the battery case was covered with a sealing body, and sealed by insulating caulking. The diameter was reduced by pressing the peripheral surface of the battery case from the outside. And the groove part formed in the opening part side of the battery case was crimped | bonded so that a battery total height might be set to 50.25 mm by pressing a battery case in a height direction. As the alkaline electrolyte, an aqueous solution containing sodium hydroxide at a concentration of 7.5 mol / L was used.

The donut-shaped insulating member was arranged on the upper part of the sealing body with the protruding portion of the positive electrode terminal protruding from the central hole of the insulating member. Next, by attaching an exterior label so as to cover the peripheral part of the sealing body (peripheral part of the insulating member disposed on the sealing body), the peripheral surface of the battery case, and the peripheral part of the bottom surface of the battery case A nickel metal hydride storage battery (A1) was obtained. A total of 50 batteries A1 were produced in the same procedure.

(4) Evaluation (a) Short-circuit test In the short-circuit test, a battery whose diameter was reduced until the outer diameter became 13.90 mm in the above (3) was used in order to make the condition that a short-circuit occurs easily.

In a 20 ° C environment, a voltage of 100 V was applied to the battery, and the resistance value was measured with a high resistance measuring device. If the resistance value was 100 MΩ or more, it was determined that there was no short circuit. Of the 50 batteries, the number of batteries in which a short circuit occurred was examined.

(B) Evaluation of N / P ratio balance (internal pressure measurement)
When the balance of the N / P ratio is lost, the reserve balance is lost, and the generation of oxygen gas during overcharge becomes significant. Therefore, in order to evaluate the balance of the N / P ratio, the internal pressure of the battery was measured. In this evaluation, in the above (3), the battery whose diameter was reduced until the outer diameter became 14.10 mm was used.

Specifically, the battery was charged at a current value of 1 It in a 40 ° C. environment until the state of charge (SOC) reached 120% of full charge, and the battery internal pressure at this time was measured. The battery of Example 1 and Comparative Example described below were evaluated with the battery internal pressure of Example 1 being 100.

Example 2
The length L ₂ of the taper portion of the negative electrode was changed from 12 mm to 6 mm. That is, the length of the taper portion is shorter than the length (10 mm) of the second separator. Except for these, 50 nickel-metal hydride storage batteries (A2) were produced and evaluated in the same manner as in Example 1.

Example 3
The 2nd separator was arrange | positioned between the 1st separator which touches a taper part, and the outer end of a positive electrode. Except these, it carried out similarly to Example 2, produced 50 nickel-metal hydride storage batteries (A3), and evaluated.

Comparative Example 1
The length L ₁ of the main body part was changed to 120 mm, the length L ₂ of the taper part was changed to 12 mm, and the length L ₃ of the thin part was changed to 23 mm so that the outer end of the positive electrode overlaps the main body part of the negative electrode ( That is, the thickness of the negative electrode active material layer in each part was adjusted so that the lengths of the main body part and the thin-walled part would have such values). The second separator was disposed between the outer end of the positive electrode and the main body of the negative electrode and between the main body and the first separator. Except these, it carried out similarly to Example 1, produced 50 nickel-metal hydride storage batteries (B1), and evaluated.

Comparative Example 2
The length L ₁ of the main body is 88 mm and the length L ₂ of the taper is 12 mm so that the outer end of the positive electrode overlaps with the thin part of the negative electrode (thin part facing the inner peripheral side of the outer end of the positive electrode). In addition, the length L ₃ of the thin portion was changed to 55 mm (that is, the thickness of the negative electrode active material layer in each portion was adjusted so that the lengths of the main body portion and the thin portion had such values). The second separator was disposed between the outer end of the positive electrode and the thin portion of the negative electrode (thin portion facing the inner peripheral side of the outer end of the positive electrode) and between the thin portion and the first separator. Except these, it carried out similarly to Example 1, produced 50 nickel-metal hydride storage batteries (B2), and evaluated.

Table 1 shows the results of Examples and Comparative Examples. The short-circuit test result is shown by the number of batteries in which a short circuit occurs in 50 batteries, and the battery internal pressure is shown as a ratio when the battery internal pressure of Example 1 is 100. Examples 1 to 3 are A1 to A3, and Comparative Examples 1 and 2 are B1 and B2.

As shown in Table 1, in the battery of Comparative Example 1, a short circuit was remarkable, and in Comparative Example 2, the battery internal pressure during overcharge was greatly increased. On the other hand, in the batteries of Examples 1, 2 and 3, almost no short circuit occurred, and the increase in battery internal pressure during overcharging was also suppressed.

The cylindrical battery according to the present invention can be used for various batteries (primary battery, secondary battery) having a wound electrode group. The cylindrical battery is particularly suitable for an alkaline storage battery such as a nickel hydride storage battery whose battery characteristics are easily affected by the N / P ratio.

1, 2: 1

Negative electrode

1a, 21a:

Body portion

1b, 21b:

Tapered portion

1c, 21c: Thin portion 2: Positive electrode 3: First separator 3a: Second separator 4: Battery case 6: Safety valve 7: Sealing plate 8: Insulation Gasket 9: Positive electrode current collector plate 11, 31: Negative electrode

current collector

12, 12a, 12b, 32, 32a, 32b, 32c: Negative electrode active material layer t _1o : Negative electrode active material layer thickness t _1i on the outer peripheral side of the main body : thickness of the negative electrode active material layer on the inner circumferential side of the main body portion t _3o: thickness t _3i of the negative electrode active material layer on the outer circumferential side of the thin portion: thickness of the negative electrode active material layer on the inner circumferential side of the thin portion

Claims

A strip-shaped positive electrode, a strip-shaped negative electrode, and an electrode group around which a strip-shaped first separator interposed between the positive electrode and the negative electrode is wound, an electrolyte, and an opening that accommodates the electrode group and the electrolyte A bottomed cylindrical battery case, and a sealing plate for sealing the opening,
The negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on both surfaces of the negative electrode current collector,
The negative electrode includes a thin portion the provided in a region of the length L 3 from the outer end of the negative electrode, and a tapered portion adjacent to the thin portion, and the other body portion,
The thickness t 1o of the negative electrode active material layer on the outer peripheral side of the main body portion and the thickness t 3o of the negative electrode active material layer on the outer peripheral side of the thin portion satisfy t 1o > t 3o ,
The thickness t 2o of the negative electrode active material layer on the outer peripheral side of the tapered portion is gradually reduced from the main body portion side toward the thin-walled portion side,
The electrode group is arranged such that an outer end of the positive electrode overlaps the taper part via the first separator, and a second electrode arranged between the outer end of the positive electrode and the taper part. A cylindrical battery further comprising a separator.
The cylindrical battery according to claim 1, wherein the second separator is disposed between the tapered portion and the first separator.
The thickness t 1i of the negative electrode active material layer on the inner peripheral side in the main body portion and the thickness t 3i of the negative electrode active material layer on the inner peripheral side in the thin-walled portion satisfy t 1i > t 3i ,
3. The cylindrical battery according to claim 1, wherein a thickness t 2i of the negative electrode active material layer on the inner peripheral side of the taper portion is gradually decreased from the main body portion side toward the thin portion side. .
The length L 2 of the tapered portion, the longer than 1/6 of the length of the outermost periphery of the negative electrode, cylindrical battery according to any one of claims 1-3.
The length L 3 of the thin portion, the negative electrode is not more than 115% more than 50% of the length of the outermost periphery of a cylindrical battery according to any one of claims 1-4.
The length of the second separator, the shorter than the length L 2 of the tapered portion, a cylindrical battery according to any one of claims 1 to 5.
The difference (t 1o -t 3o ) between the thickness t 1o of the negative electrode active material layer and the thickness t 3-o of the negative electrode active material layer is 0.01 mm or more and 0.20 mm or less. The cylindrical battery according to any one of the above.
4. The cylinder according to claim 3, wherein a difference (t 1i −t 3i ) between a thickness t 1i of the negative electrode active material layer and a thickness t 3io of the negative electrode active material layer is 0.01 mm or more and 0.20 mm or less. Battery.
The outer diameter of the cylindrical battery is 6 mm or more and 24 mm or less,
The cylindrical battery according to any one of claims 1 to 8, wherein the number of windings of the negative electrode is 2 or more and 10 or less.