Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
2002-01-09
2004-08-24
Yuan, Dah-Wei (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S233000, C429S234000, C429S241000, C429S242000
Reexamination Certificate
active
06780543
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a lithium secondary battery formed by placing at least a positive electrode, a negative electrode, and a non-aqueous electrolyte in a battery case wherein a positive electrode connecting member to which the positive electrode is connected and a negative electrode connecting member to which the negative electrode is connected are electrically separated, and a lithium secondary battery provided with a positive electrode in which a positive electrode material is adhered to a current collector, a negative electrode, and a non-aqueous electrolyte.
2. Description of the Related Art
As a secondary battery having high power and high energy density, lithium secondary batteries featuring high electromotive force derived from oxidation/reduction of lithium in the non-aqueous electrolyte have come into wide use.
Examples of such lithium secondary batteries include a coin-type lithium secondary battery wherein a separator
3
impregnated with non-aqueous electrolyte solution is sandwiched between a positive electrode
1
in which a positive electrode material is adhered to a positive electrode current collector
1
a
and a negative electrode
2
in which a negative electrode material is adhered to a negative electrode current collector
12
, and placed in a battery case
10
. The positive electrode
1
is connected to a positive electrode connecting member
11
in the battery case
10
via the positive electrode current collector
1
a
whereas the negative electrode
2
is connected to a negative electrode connecting member
12
via the negative electrode current collector
2
a
. An insulation packing
13
composed of polypropylene or the like is provided around the positive electrode connecting member
11
and the negative electrode connecting member
12
, the positive electrode connecting member
11
is bent to seal the space between the positive electrode connecting member
11
and the negative electrode connecting member
12
as shown in FIG.
1
.
In such lithium secondary battery, stainless steel or aluminum has been generally used as the positive electrode connecting member
11
in the battery case
10
, and stainless steel has been generally used as the negative electrode connecting member
12
because aluminum gets alloyed with lithium when aluminum is used.
In the above-mentioned lithium secondary battery, when the positive electrode connecting member
11
is composed of aluminum, there have remained problems that the positive electrode connecting member
11
can not be fully bent to seal the space between the positive electrode connecting member
11
and the negative electrode connecting member
12
, thus moisture comes into the battery can
10
from the sealed portion, hence storage characteristics is degraded.
On the other hand, when the positive electrode connecting member
11
is composed of stainless steel, there have remained problems that the stainless steel used as the positive electrode connecting member
11
corrodes away by the non-aqueous electrolyte solution. Especially, when cobalt-lithium oxide, nickel-lithium oxide, or manganese-lithium oxide having a spinel structure is used as the positive electrode material to obtain a lithium secondary battery having high voltage, the stainless steel used as the positive electrode connecting member
11
corrodes away more intensively, thus the storage characteristics of the lithium secondary battery is remarkably degraded.
In the ordinary lithium secondary batteries, aluminum foil, foamed aluminum, and the like have been used as the positive electrode current collector
1
a
of the positive electrode
1
.
However, when charge/discharge is carried out repeatedly to the lithium secondary battery using the positive electrode
1
in which the positive electrode material is adhered to the positive electrode current collector
1
a
consisting of aluminum foil or foamed aluminum, there have remained problems that the positive electrode material separates from the positive electrode current collector
1
a
, contact between the positive electrode material and the positive electrode current collector
1
a
is degraded, thus discharge capacity is gradually decreased, and hence sufficient charge/discharge cycle performance is not attained.
SUMMARY OF THE INVENTION
An object of the present invention is to bend a positive electrode connecting member in order to seal easily and properly a space between the positive electrode connecting member and a negative electrode connecting member in a lithium secondary battery formed by placing at least a positive electrode, a negative electrode, and a non-aqueous electrolyte in a battery case wherein the positive electrode connecting member to which the positive electrode is connected and the negative electrode connecting member to which the negative electrode is connected are electrically separated. Additional object is, in such lithium secondary battery, to prevent the positive electrode connecting member from corroding away by non-aqueous electrolyte solution, thus to improve storage characteristics of the lithium secondary battery even in a case in which cobalt-lithium oxide, nickel-lithium oxide, or manganese-lithium oxide having a spinel structure is used as a positive electrode material to obtain the lithium secondary battery having high voltage.
Another object of the present invention is, in the lithium secondary battery provided with the positive electrode in which the positive electrode material is adhered to the positive electrode current collector, the negative electrode, and the non-aqueous electrolyte, to prevent the positive electrode material from exfoliating from the positive electrode current collector when charge/discharge is carried out repeatedly so that the positive electrode material and the positive electrode current collector contact stably, thus to prevent discharge capacity from gradually decreasing for charge/discharge, hence to improve charge/discharge cycle performance of the lithium secondary battery.
A first lithium secondary battery of the present invention is formed by placing at least a positive electrode, a negative electrode, and a non-aqueous electrolyte in a battery case in which the positive electrode connecting member to which the positive electrode is connected and the negative electrode connecting member to which the negative electrode is connected are electrically separated, wherein said positive electrode connecting member is composed of clad material comprising one of aluminum or aluminum alloy and one of austenitic stainless steel or ferrite stainless steel, and the aluminum or aluminum alloy in the clad material is set in the positive electrode side.
As the above-mentioned first lithium secondary battery, when the clad material comprising one of aluminum or aluminum alloy and one of austenitic stainless steel or ferrite stainless steel is used as the positive electrode connecting member, strength of the clad material is higher compared with the case where only aluminum is used, thus the positive electrode connecting member is properly bent in order to seal fully the space between the positive electrode connecting member and the negative electrode connecting member. As a result, moisture is prevented from coming into the battery can from a sealed portion, hence storage characteristics of the lithium secondary battery is improved.
As the above-mentioned first lithium secondary battery, when the aluminum or aluminum alloy in the positive electrode connecting member which is composed of the clad material is set in the positive electrode side, the positive electrode connecting member is prevented from corroding away by the non-aqueous electrolyte solution even in a case in which cobalt-lithium oxide, nickel-lithium oxide, or manganese-lithium oxide having the spinel structure is used for the positive electrode of the lithium secondary battery to obtain the lithium secondary battery having high voltage. In the clad material, a resistant alloy is formed in the inter
Kamino Maruo
Nakajima Hiroshi
Yoshimura Seiji
Sanyo Electric Co,. Ltd.
Westerman Hattori Daniels & Adrian LLP
Yuan Dah-Wei
LandOfFree
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