JP2006040652A - Storage element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high power storage element with a high production yield. <P>SOLUTION: A manufacturing method of the storage element comprises the following steps of: inserting an electrode group, which is formed by winding a strip-like positive and negative electrode sheets, and a separator, into a bottom-closed can; sealing the opening of the bottom-closed can with a sealing plate; forming a collector exposure portion continuously in a longitudinal direction on an electrode sheet of at least either one of a positive or negative electrode on which an electrode sheet is not stuck; welding together the collector exposure portion and a collecting terminal plate; disposing the collecting terminal plate onto the bottom inside of the bottom-closed can; and electrically connecting the collecting terminal plate and the sealing plate having a terminal with a collecting lead wire. As a result, respective terminals and collecting lead wire are welded before the electrode group is inserted into the bottom-closed can, thereby enabling the maintenance appropriately by checking with eyes. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a power storage element suitable for high output, and more particularly to a current collection structure that can easily determine a process failure while reducing internal resistance.

  Power storage elements, particularly secondary batteries such as lithium ion batteries and nickel metal hydride batteries, are used as main power sources for various cordless devices such as mobile phones. However, in recent years, as lithium ion batteries that are light in addition to high energy density are attracting attention, as practical studies for driving power sources for electric vehicles and electric tools are activated. A secondary battery used for a main power source of a cordless device generally has a structure as shown in FIG. That is, a positive electrode material is applied to a positive electrode current collector, a strip-like positive electrode plate 1 having a current collecting lead 1a welded to one end in the longitudinal direction, and a negative electrode mixture is applied to the negative electrode current collector, A strip-shaped negative electrode plate 2 having a current collecting lead 2a welded to one end in the longitudinal direction is wound in a spiral shape through a separator 3 to form an electrode plate group, and then this electrode group is inserted into a bottomed can. The positive electrode current collecting lead 1a is welded to the terminal of the sealing plate disposed on the opening side, and the negative electrode current collecting lead 2a is welded to the bottom of the bottomed can that also serves as the terminal, and then sealed. (For example, Patent Document 1). While this method is simple and has the advantage that the manufacturing cost can be reduced, both positive and negative electrodes have low current collection efficiency and high internal resistance because electron conductivity is ensured only with current collecting leads. Have

Therefore, a secondary battery that requires a high output, such as for a power tool, has been improved to have a structure as shown in FIG. 4 in order to increase current collection efficiency. That is, a strip-like positive electrode plate 1 in which a positive electrode material is applied to a positive electrode current collector, and a current collector exposed portion 1b to which no electrode plate material is attached is continuously provided in the longitudinal direction, and a negative electrode current collector A strip-shaped negative electrode plate 2 provided with a current collector exposed portion 2b continuously coated with a negative electrode mixture and having no electrode plate material attached in the longitudinal direction thereof is spirally formed with a separator 3 interposed therebetween. After winding, the current collector exposed portion 1b of the positive electrode plate 1 from one side and the current collector exposed portion 2b of the negative electrode plate 2 projecting from the other to form an electrode plate group, and then the current collector exposed portions 1b and 2b and The electric terminal plate 4 was collectively welded, and this electrode plate group was inserted into a bottomed can. The negative electrode current collecting lead 2a integrated with the current collecting terminal plate 4 on the bottom side is welded to the bottom of the bottomed can which also serves as a terminal, and the positive current collecting integrated with the current collecting terminal plate 4 on the opening side The electric lead 1a is welded to a terminal of a sealing plate and then sealed (for example, Patent Document 2). Since this current collection structure can extract electrons from each part of the electrode, the current collection efficiency is improved as compared with the structure shown in FIG. 1, and it is suitable for high output applications.
Japanese Utility Model Publication No. 63-26973 JP 2000-294222 A

However, in the structure of Patent Document 2, as described above, the current collector terminal plate on the bottom side and the bottom of the bottomed can must be welded after the electrode group is inserted into the bottomed can. In such a case, defects caused by insufficient process management, such as melting of the separator due to sparks during welding, cannot be visually determined, so the short-circuit inspection (voltage measurement) is a subsequent process without noticing the management of the welding process. ) Has a problem of discharging a considerable amount of defective batteries.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-described problems and to provide a high-output power storage device that can improve production yield by visually determining defective products in a welding process and has high current collection efficiency. And

In order to solve the above-mentioned problem, the present invention provides a first aspect in which an electrode group constituted by winding a belt-like positive electrode plate and a negative electrode plate and a separator is inserted into a bottomed can, and the opening is used as a sealing plate. For the electricity storage device that is sealed, a current collector exposed portion to which no electrode plate material is attached is continuously provided in the longitudinal direction of either the positive electrode plate or the negative electrode plate. The current collector terminal plate and the current collecting terminal plate are welded together, and this current collecting terminal plate is arranged on the bottom side of the bottomed can, and the current collecting terminal plate and the sealing plate having the terminals are electrically connected by a current collecting lead. It is characterized by doing.
According to a fourth aspect of the present invention, there is provided an electricity storage device in which an electrode group formed by winding a belt-like positive electrode plate and negative electrode plate and a separator is inserted into a bottomed can and the opening is sealed with a sealing plate. A collector exposed portion to which no electrode plate material is attached is continuously provided in the longitudinal direction of the positive electrode plate and the negative electrode plate, and the collector exposed portion and the current collector terminal plate are collectively welded to form a bottomed can The current collecting terminal plate on the bottom side of the electrode is electrically connected to a sealing plate having a terminal by a current collecting lead, and the current collecting lead connected to the sealing plate is arranged along the outer edge of the electrode group. And
By adopting a structure in which the current collector exposed portion and the current collector terminal plate can be collectively welded before being inserted into the bottomed can, it is possible to provide a power storage element with a high production yield while maintaining a high output. .

  ADVANTAGE OF THE INVENTION According to this invention, the electrical storage element suitable for a high output use can be provided with a high production yield.

  Here, as an example of the storage element, a detailed form and a configuration procedure of a lithium ion battery will be described with reference to FIGS.

As the positive electrode active material, a lithium composite oxide represented by a general formula LiMO ₂ or LiM ₂ O ₄ can be used. M in the above general formula can be selected from one or more transition metal elements such as cobalt, nickel, and manganese. Further, a part of the transition metal element can be replaced with a typical metal element such as aluminum or magnesium.

  These positive electrode active materials are mixed with a conductive agent (graphite, carbon black, metal powder, etc. stable under the positive electrode potential) and a binder (polyvinylidene fluoride (PVDF), polytetrafluoroethylene (stable under the positive electrode potential) ( PTFE) or the like is used, and is applied to a current collector (aluminum foil or perforated body is used) to produce a strip-like positive electrode plate 1.

  As the negative electrode active material, natural graphite, artificial graphite, aluminum, various alloys mainly composed thereof, metal oxides such as tin oxide, and metal nitrides can be used. These negative electrode active materials are made of a conductive agent (graphite, carbon black, metal powder, etc. stable under negative electrode potential) and a binder (styrene-butadiene copolymer rubber (SBR) / carboxy stable under negative electrode potential). A belt-like negative electrode plate 2 is produced by kneading with methylcellulose (CMC) or the like and applying it to a current collector (a copper foil, a copper perforated body or the like is used).

  Here, at least one of the strip-like positive and negative electrode plates 1 or 2 is provided with a current collector exposed portion 1b or 2b in which no electrode plate material is adhered in the longitudinal direction in order to establish the current collecting structure of the present application. Need to be. The current collector exposed portion 1b or 2b is collectively welded to the current collector terminal plate 4. As a method of collective welding, it is preferable to use laser welding or resistance welding from the viewpoint of reducing contact resistance.

Here, when the current collector exposed portion 2b is provided only on one electrode plate (here, the negative electrode plate 2) as shown in FIG. 1, the current collector terminal plate 4 is disposed on the bottom side of the bottomed can. The negative electrode current collecting lead 2a integrated with the plate 4 is arranged so as to go to the opening along the space existing at the outer edge of the electrode group or the winding center part of the electrode group. From the positive electrode plate 1, only the current collecting lead 1 a is arranged to face the opening. The current collecting leads 1a and 2a are each welded to a terminal provided on a sealing plate, and are then inserted into a bottomed can and sealed to form the power storage device of the present application.
If the current collector terminal plate 4 is collectively welded to the current collector exposed portion 1b of the positive electrode plate 1 and disposed on the opening side of the bottomed can, the current collecting lead 2a of the negative electrode plate 2 as shown in FIG. It is necessary to lengthen in order to weld the terminal of the sealing plate. Since the negative electrode plate 2 does not use the current collecting terminal plate 4, the current collecting efficiency is lower than that of the positive electrode plate 1, and the current collecting efficiency is further lowered by extending the current collecting lead 2 a, which is not preferable.

  Further, when the collector exposed portions 1b and 2b are provided on both electrode plates as shown in FIG. 2, the negative electrode current collecting lead integrated with the current collecting terminal plate 4 arranged on the bottom side of the bottomed can. 2a is disposed so as to face the opening along the outer edge of the electrode group, and the positive electrode current collecting lead 1a integrated with the current collecting terminal plate 4 is welded to the terminal provided on the sealing plate. By being inserted into the bottom can and sealed, the power storage element of the present application is obtained.

The nonaqueous electrolytic solution impregnated in the electrode plate group described above is composed of a solute and a nonaqueous solvent. Examples of the solute include lithium salts such as lithium hexafluorophosphate (LiPF ₆ ) and lithium tetrafluoroborate (LiBF ₄ ). As the non-aqueous solvent, cyclic carbonates such as ethylene carbonate and propylene carbonate, and chain carbonates such as dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate are preferable, but not limited thereto. The non-aqueous solvent may be used alone or in combination of two or more. Examples of the additive include vinylene carbonate, cyclohexyl benzene, and diphenyl ether.

  In addition, although what was mentioned above was a form and structure procedure of a lithium ion battery, also when constructing secondary batteries, such as a nickel metal hydride storage battery and a nickel cadmium storage battery, or an electric double layer capacitor, the material generally used is used. By making full use, the effects of the present invention can be utilized in the same manner as described above. Further, in FIGS. 1 and 2, the negative electrode plate is arranged to be the bottom of the bottomed can, but the same effect can be obtained even if the arrangement of the positive electrode plate and the negative electrode plate is reversed.

Examples of the present invention are specifically shown below.
Example 1
(Preparation of positive electrode plate)
85 parts by weight of lithium cobaltate powder, 10 parts by weight of carbon powder as a conductive agent, 5 parts by weight of PVDF as a binder, and N-methyl-2-pyrrolidone (hereinafter referred to as NMP) as a solvent were mixed. This mixture was applied to an aluminum foil current collector having a thickness of 15 μm, dried, then rolled to a thickness of 100 μm, and a current collecting lead 1a was welded to one end in the longitudinal direction to produce a belt-like positive electrode plate 1. .
(Preparation of negative electrode plate)
95 parts by weight of artificial graphite powder and 5 parts by weight of PVDF as a binder were mixed using NMP. This mixture is applied to a copper foil current collector having a thickness of 10 μm, dried, and then rolled to have a thickness of 110 μm, so that the current collector exposed portion 2b having no electrode plate material attached to one side in the longitudinal direction is continuously formed. A belt-like negative electrode plate 2 was prepared.
(Production of battery)
As the separator 3, a polypropylene resin microporous film having a thickness of 25 μm was used to constitute the electrode group shown in FIG. 1. The current collecting leads 1a and 2a were welded to the terminals of the sealing plate, and the electrode group was inserted into a bottomed can. In this bottomed can, lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a non-aqueous solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 1: 1 as a non-aqueous electrolyte so as to be 1 mol / L. A cylindrical lithium ion battery having a diameter of 26 mm, a height of 95 mm, and a theoretical capacity of 3000 mAh was produced by injecting the prepared material and fitting a sealing plate into the opening of the bottomed can. This is referred to as the battery of Example 1.
Example 2
A battery similar to that of Example 1 was prepared except that a current collector exposed portion 1b to which no electrode plate material was attached was continuously provided on one side in the longitudinal direction of the positive electrode plate 1 to obtain the structure shown in FIG. did. This is referred to as the battery of Example 2.
<< Comparative Example 1 >>
A battery was prepared in the same manner as in Example 1 except that the current collecting lead 2a was welded to one end in the longitudinal direction of the negative electrode plate 2 to obtain the structure shown in FIG. This is referred to as the battery of Comparative Example 1.
<< Comparative Example 2 >>
A battery similar to that of Example 1 was produced except that a current collector exposed portion 1b to which no electrode plate material was attached was continuously provided on one side in the longitudinal direction of the positive electrode plate 1 to obtain the structure shown in FIG. did. This is referred to as the battery of Comparative Example 2.
<< Comparative Example 3 >>
A current collector exposed portion 1b to which no electrode plate material is attached is continuously provided on one side in the longitudinal direction of the positive electrode plate 1, and a current collecting lead 2a is welded to one end in the longitudinal direction of the negative electrode plate 2 A battery similar to that of Example 1 was produced except that the structure shown in FIG. This is referred to as the battery of Comparative Example 3.

The following evaluation was performed with respect to the above battery. The results are shown in (Table 1).
(Welding inspection)
By coating the tip of the copper electrode for welding with copper oxide powder, defects in the welding process occurred intentionally. In this state, positive and negative current collecting leads 1a and 2a were welded to the respective terminals. When melting of the separator due to spark during welding could be visually confirmed, the tip of the copper electrode was polished and welding was resumed. In this way, 100 batteries were continuously produced for each example and comparative example, and defective batteries that could be visually confirmed were excluded.
(Short-circuit inspection)
The battery that passed the above-described welding failure inspection was charged at 300 mA until the voltage reached 4.1 V, and the initial open circuit voltage V ₁ was measured. Further, this battery was allowed to stand for 7 days in a 45 ° C. environment, and the open circuit voltage V ₂ after the standing was measured. A battery in which the open circuit voltage difference (V ₁ −V ₂ ) exceeded 0.3 V was excluded as a short circuit defective battery.
(Discharge characteristics)
Five batteries were extracted from the battery that passed the short-circuit inspection described above, and discharged at 300 mA until the voltage reached 3V. Subsequently, the battery was charged at 300 mA until the voltage reached 4.2 V, and then discharged at 300 mA until the voltage reached 3 V to obtain a low current discharge capacity A ₁ . The battery was further charged at 300 mA until the voltage reached 4.2 V, and then discharged at 3000 mA until the voltage reached 3 V to obtain a high current discharge capacity A ₂ . The average value of the ratio (A ₂ / A ₁ ) between the low current discharge capacity and the high current discharge capacity thus obtained was determined.

比較例１〜２は、溶接検査で不良として排出された電池がゼロであった。これは溶接不良が発生しなかったからではなく、有底缶内でスパークが起こったため目視できなかったためである。したがって適切なメンテナンスができないまま溶接を続行したため、その後の短絡検査において、セパレータの溶融に端を発する顕著な短絡（電圧降下）を起こす電池が多発した。

In Comparative Examples 1 and 2, the batteries discharged as defects in the welding inspection were zero. This is not because no welding failure occurred, but because the spark occurred in the bottomed can and was not visible. Therefore, welding was continued without proper maintenance, and in subsequent short-circuit inspections, many batteries caused a remarkable short-circuit (voltage drop) that started with the melting of the separator.

  On the other hand, in Examples 1 and 2 and Comparative Example 3 which are the inventions of the present application, since welding inspection was performed in a visible state before being inserted into the bottomed can, welding failure (melting of the separator due to spark during welding) was performed. ), And after proper maintenance (polishing of the copper electrode tip), welding could be resumed. Therefore, since subsequent welding defects could be suppressed, a high yield could be secured without causing short circuit defects.

  However, in Comparative Example 3, since the current collecting lead 2a of the negative electrode plate 2 not using the current collecting terminal plate 4 was considerably long, the deterioration of the discharge characteristics due to the decrease in current collecting efficiency was observed. Therefore, in order to adopt a structure in which the electrode group is inserted into the bottomed can after welding, which is the main trunk of the present invention, the electrode plate on the side where the lead for current collection is taken out from the bottom is used in accordance with the utilization of the current collector terminal plate. It was found that the adoption of an electrode plate structure (continuous installation of the current collector exposed part) was indispensable.

  As described above, by using the current collecting structure of the present invention, a high-output power storage element can be provided with a high yield. The power storage device according to the present invention is suitable for a drive power source such as an electric vehicle or a power tool that requires large current charge / discharge.

Schematic of the electrode group in the lithium ion battery of Example 1 of the present invention Schematic of the electrode group in the lithium ion battery of Example 2 of the present invention Schematic of the electrode group in the lithium ion battery of Comparative Example 1 Schematic of the electrode group in the lithium ion battery of Comparative Example 2 Schematic of the electrode group in the lithium ion battery of Comparative Example 3

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode plate 1a Positive electrode collector lead 1b Positive electrode collector exposed part 2 Negative electrode plate 2a Negative collector lead 2b Negative electrode collector exposed part 3 Separator 4 Current collector terminal board

Claims (4)

An electrode group formed by winding a strip-like positive electrode plate with a positive electrode material attached to a positive electrode current collector, a belt-like negative electrode plate with a negative electrode material attached to a negative electrode current collector, and a separator, Is an electricity storage element that is inserted into the opening and sealed with a sealing plate,
(I) Either one of the positive electrode plate or the negative electrode plate is continuously provided with a collector exposed portion to which no electrode plate material is attached in the longitudinal direction;
(Ii) The current collector exposed portion is collectively welded to the current collector terminal plate,
(Iii) The current collector terminal plate is disposed on the bottom side of the bottomed can,
(Iv) The electricity storage element, wherein the current collecting terminal plate is electrically connected to the sealing plate having a terminal through a current collecting lead. The power storage element according to claim 1, wherein a current collecting lead connected to the current collecting terminal plate is disposed along an outer edge of the electrode group. The power storage element according to claim 1, wherein a current collecting lead connected to the current collecting terminal plate is disposed along a space existing in a winding center portion of the electrode group. An electrode group configured by winding a strip-like positive electrode plate with a positive electrode material attached to a positive electrode current collector, a belt-like negative electrode plate with a negative electrode material attached to a negative electrode current collector, and a separator, Is an electricity storage element that is inserted into the opening and sealed with a sealing plate,
(I) The positive electrode plate and the negative electrode plate are continuously provided with a current collector exposed portion to which no electrode plate material is attached in the longitudinal direction,
(Ii) The current collector exposed portion is collectively welded to the current collector terminal plate,
(Iii) The current collector terminal plate disposed on the bottom of the bottomed can is electrically connected to the sealing plate having a terminal through a current collecting lead,
(Iv) A power storage element, wherein a current collecting lead connected to the sealing plate is disposed along an outer edge of the electrode group.

Images