Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Intracell assembly having cell electrode connector
Reexamination Certificate
2000-04-26
2002-04-16
Kalafut, Stephen (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Intracell assembly having cell electrode connector
C429S211000, C429S146000, C429S186000, C429S247000
Reexamination Certificate
active
06372380
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a secondary battery using a nonaqueous electrolyte, and more particularly to a nonaqueous electrolyte secondary battery capable of charge and discharge at a high current density.
A lithium ion secondary battery is a typical one of nonaqueous electrolyte secondary batteries. The lithium ion secondary battery uses a negative electrode and a positive electrode, wherein the negative electrode may be doped and de-doped with lithium, and the positive electrode contains a transition metal oxide. The negative electrode is shaped in sheet. The sheet-shaped negative electrode comprises a sheet-shaped negative electrode collector applied with a negative electrode active material.
The positive electrode is shaped in sheet. The sheet-shaped positive electrode comprises a sheet-shaped positive electrode collector applied with a positive electrode active material. The lithium ion secondary battery has a lamination structure of the negative and positive electrodes which are separated through a separator. The lamination structure may be coated with a packaging material. Alternatively, the lamination structure may be rolled to form a cylindrically shaped roll structure which is contained in a battery case.
The later one having the cylindrically shaped roll structure contained in a battery case is particularly superior in sealing characteristic. The cylinder shape allows a uniform battery reaction over position of the lamination structure. The nonaqueous electrolyte secondary battery is used for obtaining a large current. The cylinder shape is important for the nonaqueous electrolyte secondary battery. The cylindrically shaped nonaqueous electrolyte secondary battery is expected as a large battery for driving an electric car or an electric auxiliary bicycle.
FIG. 1
is a fragmentary cross sectional elevation view illustrative of a conventional cylindrically shaped nonaqueous electrolyte secondary battery.
A battery
51
has a battery case
52
which accommodates a battery element
56
which comprises a roll structure of laminations of sheet-shaped negative and positive electrodes
53
and
54
separated by a separator
55
, wherein the negative electrode
53
comprises a negative electrode collector provided with a negative electrode active material, whilst the positive electrode
54
comprises a positive electrode collector provided with a positive electrode active material. The separator
55
is wider than the negative and positive electrodes
53
and
54
. The battery case
52
is cylindrically shaped to accommodate the cylindrically shaped roll structure of the laminations. The lamination structure is rolled around a center axis of the cylinder A width direction of the separator
55
and the negative and positive electrodes
53
and
54
corresponds to the direction of the center axis of the cylinder. The separator
55
is wider than the negative and positive electrodes
53
and
54
, so that opposite sides of the cylindrically shaped battery element
56
comprise side portions of the separator
55
, wherein the side portions of the separator
55
project from the side portions of the negative and positive electrodes
53
and
54
. The battery case
52
may serve as a negative electrode terminal. In this case, the sheet shaped negative electrode is attached with a stripe-shaped negative electrode lead
57
. This stripe-shaped negative electrode lead
57
is welded to an inner wall of the battery case
52
. A positive electrode lead
58
is attached to a battery header
59
. The battery header
59
serves as a positive electrode terminal. The battery header
59
has a pressure release valve which releases an internal pressure of the battery if the internal pressure is excessively increased.
In the above battery, the stripe-shaped electrode leads are attached to the collectors. If the large current is fetched from the battery, a current distribution is different between a position adjacent to an attachment position of the electrode lead and a position far from the electrode lead. In Japanese laid-open patent publication No. 7-192717, it is disclosed that in order to solve the above problem, the electrode lead is used which has a large sectioned area. Also, it is disclosed that a large number of the electrode leads are attached, thereby making an attachment portion of the electrode lead thick, resulting in a non-uniform distance between the positive and negative electrodes in the form of the roll structure. This provide undesired influence to the characteristics of the battery,
In Japanese laid-open patent publication No. 6-36756, it is disclosed that in order to fetch the current uniformly over the positions of the roll structure, a nickel-cadmium battery of a sintered type is provided wherein a large number of plate-shaped collectors are connected to a sealing cap provided in the battery case, and a metal spring is provided to contact with the sealing cap and the collectors to form a conduction path between the sealing cap and the collectors.
In Japanese laid-open utility model publication No. 5-45898, it is disclosed that a metal foam is provided to form a current divided path.
The formation of the current divided path provides an effect of reduction in IR loss as compared to when only the electrode leads are provided, but this effect is not so different from when a large number of the electrode leads is provided. If this technique is applied to the nonaqueous electrolyte secondary battery, then problems are raised with a possible breaking of connecting part of the electrode leads due to vibration of the battery.
In order to connect the electrode leads to the positive electrode collector and the negative electrode collector, it is necessary that a positive electrode active material and a negative electrode active material are applied on the positive electrode collector and the negative electrode collector before the metal strips are bonded by a welding method to active-material-stripped faces of the connecting parts of the electrode leads. In order to reduce the IR loss, a large number of the electrode leads are plugged to take a long time for connecting the electrode leads. This means that the fabrication processes are complicated.
In Japanese laid-open patent publication No. 9-306465, there is disclosed a nickel-hydrogen secondary battery using a winding type battery element, wherein the number of the connecting parts, per one turn or one round, of the electrode plates connected to the collector terminal is increased from an innermost position to an outermost position so as to improve uniformity of the current fetch from the roll body. It is, however, necessary that the electrode plates are bonded by a welding method to the collector terminal. This bonding process makes long the necessary time for the fabrication of the battery.
In the above circumstances, it had been required to develop a novel nonaqueous electrolyte secondary battery free from the above problem.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a novel nonaqueous electrolyte secondary battery free from the above problems.
It is a further object of the present invention to provide a novel nonaqueous electrolyte secondary battery which is capable of reducing an IR loss even in a highly efficient discharge process.
It is a still further object of the present invention to provide a novel nonaqueous electrolyte secondary battery preventing a conductive connection between a battery element and a battery case from being broken due to vibration of the battery.
It is yet a further object of the present invention to provide a novel nonaqueous electrolyte secondary battery having a highly reliability.
It is yet a further object of the present invention to provide a novel nonaqueous electrolyte secondary battery which allows simplifying the fabrication processes.
It is yet a further object of the present invention to provide a novel nonaqueous electrolyte secondary battery which allows shortening the necessary time for the fabricati
Kitami Tsuyoshi
Suzuki Hiromi
Alejandro R.
Kalafut Stephen
NEC Corporation
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