Chemistry: electrical current producing apparatus – product – and – Plural concentric or single coiled electrode
Reexamination Certificate
2000-06-28
2002-08-13
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Plural concentric or single coiled electrode
C429S161000, C429S211000, C029S623100
Reexamination Certificate
active
06432574
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a nonaqueous electrolyte secondary battery, and more particularly to a nonaqueous electrolyte secondary battery capable of highly efficient charge and discharge.
A typical one of the nonaqueous electrolyte secondary batteries is a lithium ion secondary battery having a negative electrode which may be doped and de-doped with lithium and a positive electrode including a transition metal oxide. The negative electrode comprises a stripe-shaped negative electrode collector applied with a negative electrode active material. The positive electrode comprises a stripe-shaped positive electrode collector applied with a positive electrode active material. The negative electrode and the positive electrode sandwich a separator to form a lamination structure. The lamination structure is enclosed in a package. Alternatively, it is possible that the lamination structure is rolled to form a cylindrically shaped battery element so called as a Jelly-roll so that the cylindrically shaped battery element is accommodated in a cylindrically shaped battery can.
The cylindrically shaped battery is superior in seal-ability and allows a uniform battery reaction over sites of the cylindrically shaped battery element. If the nonaqueous electrolyte secondary battery is required to supply a large current, then the cylindrically shaped battery is suitable and important. The cylindrically shaped nonaqueous electrolyte secondary battery is attractive as a large battery for electric car, electric auxiliary bicycle and the like.
FIG. 1A
is a cross sectional elevation view illustrative of a conventional cylindrically shaped nonaqueous electrolyte secondary battery.
FIG. 1B
is a view illustrative of a pair of positive and negative electrodes included in the conventional cylindrically shaped nonaqueous electrolyte secondary battery shown in FIG.
1
A.
FIG. 1C
is a schematic perspective view illustrative of a cylindrically shaped battery element comprising a rolled structure of laminations of a separator sandwiched by positive and negative electrodes included in the conventional cylindrically shaped nonaqueous electrolyte secondary battery shown in FIG.
1
A.
A cylindrically shaped nonaqueous electrolyte secondary battery
51
comprises a cylindrically shaped battery can
52
and a cylindrically shaped battery element
56
contained in the cylindrically shaped battery can
52
. The cylindrically shaped battery element
56
comprises a rolled structure of laminations of stripe-shaped positive and negative electrodes
54
and
53
sandwiching a stripe-shaped separator
55
. The stripe-shaped positive electrode
54
comprises a stripe-shaped positive electrode collector applied with a positive electrode active material. The stripe-shaped negative electrode
53
comprises a stripe-shaped negative electrode collector applied with a negative electrode active material. The stripe-shaped separator
55
is wider in width than the stripe-shaped negative and positive electrodes
53
and
54
, so that opposite sides of the laminations comprise opposite sides of the stripe-shaped separator
55
. Thus, opposite ends of the rolled structure of the laminations comprise opposite sides of the stripe-shaped separator
55
. The cylindrically shaped battery can
52
may serve as a negative electrode side terminal, wherein the stripe-shaped negative electrode
53
is electrically connected to the cylindrically shaped battery can
52
through a negative electrode tab
57
. A first end of the negative electrode tab
57
is bonded to the stripe-shaped negative electrode
53
and a second end of the negative electrode tab
57
is bonded by welding to an inner wall of the cylindrically shaped battery can
52
.
If the cylindrically shaped nonaqueous electrolyte secondary battery is required to perform highly efficient charge and discharge operations, then a plurality of negative electrode tabs are bonded by welding to the inner wall of the cylindrically shaped battery can in order to reduce an IR-loss and allow a uniform battery reaction.
Positive electrode tabs
58
are also provided. A first end of each of the positive electrode tabs
58
is bonded to the stripe-shaped positive electrodes
54
and a second end of the positive electrode tabs
58
is bonded to a battery header
59
which serves as a positive electrode side terminal. The battery header
59
is provided with a pressure release valve or a pressure control valve for releasing an internal pressure of the battery if the internal pressure is excessively increased.
As shown in
FIG. 1B
, the stripe-shaped positive electrode
54
comprises the stripe-shaped positive electrode collector applied with the positive electrode active material except for a one-side active material free region. Namely, the one side active material free region is not applied with the positive electrode active material. The positive electrode tabs
58
are bonded by welding to the one-side active material free region of the stripe-shaped positive electrode collector of the stripe-shaped positive electrode
54
. Also, the stripe-shaped negative electrode
53
comprises the stripe-shaped negative electrode collector applied with the negative electrode active material except for a one-side active material free region. Namely, the one side active material free region is not applied with the negative electrode active material. The negative electrode tabs
57
are bonded by welding to the one-side active material free region of the stripe-shaped negative electrode collector of the stripe-shaped negative electrode
53
. The stripe-shaped negative and positive electrodes
53
and
54
sandwich the stripe-shaped separator
55
to form the lamination. The lamination is then rolled to form the rolled structure of the lamination, wherein the rolled structure forms the cylindrically shaped battery element as shown in FIG.
1
C. The cylindrically shaped battery element is accommodated in the cylindrically shaped battery can
52
. The negative electrode tabs
57
and the positive electrode tabs
58
are so long as to increase the losses of currents at the negative electrode tabs
57
and the positive electrode tabs
58
. It is also difficult to make uniform the length of the plural electrode leads, the current losses are likely to be non-uniform between the negative electrode tabs
57
and the positive electrode tabs
58
. This may cause that part of the negative electrode tabs
57
and the positive electrode tabs
58
shows a heat generation. The current distribution is different between the adjacent part and far apart from the bonding part of each of the negative electrode tabs
57
and the positive electrode tabs
58
. Those make it difficult to realize the highly efficient charge and discharge operations.
In Japanese laid-open patent publication No. 7-6749, it is disclosed that a cylindrically shaped secondary battery has positive and negative electrodes and collector terminals with comb-teeth shaped welding portions. This publication also discloses a method of the cylindrically shaped secondary battery.
This conventional method utilizes a spot welding where a welding current is concentrated to projecting portions of the collector. The available electrode materials are limited to materials such as nickel allowing the spot welding. it is also necessary that the separator is thermally stable to the heat generation due to the spot welding.
In Japanese laid-open patent publication No. 9-306465, it is disclosed that a cylindrically shaped secondary battery increases in the number of connecting parts between the positive and negative electrodes and the collectors from the most inner portion to the most outer portion of the cylindrically shaped battery element.
The positive and negative electrodes are connected to the collectors by the spot welding. This spot welding is carried out by plural times of contact of a welding rod to different positions, for which reason it is difficult to realize the exactly desired welding. Further, the electrode material is limited t
Inoi Takayuki
Kitami Tsuyoshi
Saito Susumu
Suzuki Hiromi
Chaney Carol
NEC Corporation
Tsang-Foster Susy
Young & Thompson
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