Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Reexamination Certificate
1999-10-28
2002-08-13
Chaney, Carol (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
C429S472000, C429S094000, C429S170000
Reexamination Certificate
active
06432578
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates to a small-sized portable sealed cell, and particularly, to a technique for preventing a disconnection of an electrode current collector tab in a laser-sealed ion cell.
(2) Description of the Prior Art
The Applicants of the present invention disclosed in Japanese Unexamined Patent Publication No. 9-171809, a small-sized portable sealed cell which is sealed by laser-welding a sealing lid to an open rim (end) of a cell outer can accommodating a power-generating component. In this cell, either core body of a positive electrode plate and a negative electrode plate is disposed on the outermost periphery of the power-generating component, an approximately U-shaped slit (a cutting line) is formed in a portion of the exposed core body, and a current collector tab is formed by folding the incised portion formed by the slit in a direction of an opening of the cell outer can. The current collector tab is held between the open rim (end) of the cell outer can and the sealing lid, and the cell is sealed by laser-welding these three members, the current collector tab, the open rim of the cell outer can, and the sealing lid, in this state. Simultaneously, an electric connection of a positive electrode or a negative electrode in the power-generating component to the cell outer can is further improved.
Since this cell is related directly to the point of the present invention, an example of the cell is described below in detail with reference to the drawings.
FIGS.
9
(
a
) and
9
(
b
) show a construction of a positive electrode plate
20
.
FIG.
9
(
a
) is a side view of the positive electrode plate and FIG.
9
(
b
) is a front view of it. As shown in the Figures, the positive electrode plate
20
is constructed by applying a positive electrode active material (slurry)
22
consisting of LiCoO
2
(the main component), graphite, carbon black, and N-methyl-2-pyrrolidone-containing polyvinylidene fluoride to both sides, in principle, of a slender and thin positive electrode core body 21 made of aluminum foil with a length of 335 mm, a width of 38 mm and a thickness of 20 &mgr;m; by pressing the core body
21
with the positive electrode active material (slurry)
22
; and by depositing the slurry by vacuum drying. An approximately U-shaped incised portion
23
is provided on the outermost periphery of the positive electrode core body
21
, which is inserted into the cell outer can.
Both sides of a 20 mm-long portion at the end of the roll of the positive electrode core body
21
, which is provided with the incised portion
23
, do not have the positive electrode active material
22
, thereby serving as an exposed core body portion (a two-side exposed portion). In addition, a 50 mm-long portion of the positive electrode core body
21
extending from the end of the two-side exposed portion to the side of a rolling-starting end is formed to have the positive electrode active material
22
only on one side thereof, thereby serving as an exposed core body portion with the other side exposed (a one-side exposed portion). The reason for forming the above-mentioned one-side exposed portion is to electrically connect the cell outer can, also functioning as a positive electrode external terminal, to a positive electrode by contacting the one-side exposed portion to the internal surface of the cell outer can.
FIGS.
10
(
a
) and
10
(
b
) show a construction of a negative electrode plate
30
.
FIG.
10
(
a
) is a side view of the negative electrode plate and FIG.
10
(
b
) is a front view of it. As shown in the Figures, the negative electrode plate
30
is constructed by applying a negative electrode active material
32
consisting of powdery natural graphite (the main component) and N-methyl-2-pyrrolidone-containing polyvinylidene fluoride to both sides of a slender and thin negative electrode core body
31
made of copper foil with a length of 315 mm, a width of 39 mm, and a thickness of 18 &mgr;m; and by depositing the negative electrode active material
32
through drying and pressing. Furthermore, a negative electrode lead
33
made of nickel is attached as a negative electrode current collector directly to the negative electrode core body
31
made of copper foil in the portion of a roll axis described later.
FIG. 11
shows a construction of a spirally-wound electrode body
40
.
As shown in
FIG. 11
, the spirally-wound electrode body
40
is formed by rolling the positive electrode plate
20
and the negative electrode plate
30
with a separator
41
, which is made of polyethylene and slightly wider than both plates. In this case, because of the above-mentioned reason, the plates are rolled so that the one-side exposed portion, with no positive electrode active material
22
applied, of the positive electrode plate
20
is located on the outermost periphery of the spirally-wound electrode body
40
. The rolling-terminal portion of the spirally-wound electrode body
40
is fastened with an adhesive tape (not shown), and the bottom of the spirally-wound electrode body
40
is covered with an insulating tape (not shown) for preventing the contact with the cell can.
A positive electrode current collector tab is formed by folding the incised portion
23
shown in FIG.
9
. The above-mentioned incised portion
23
is provided in a position where the electrode plate of the same polarity is located in an internal roll axis of the cell so that the internal short-circuit does not occur even if the burrs in the incised portion
23
damage the separator
41
.
FIGS.
12
(
a
) and
12
(
b
) show a construction of a sealing lid
50
.
FIG.
12
(
a
) is a partially sectional side view of the sealing lid from which a cell cap is removed. FIG.
12
(
b
) is a perspective view of the sealing lid as viewed from a lower side thereof.
As shown in FIGS.
12
(
a
) and
12
(
b
), the sealing lid
50
includes the sealing plate
51
having a through-hole formed in the central portion thereof a metallic hollow cap
53
fitted in the through-hole with the intervention of an insulating gasket
52
, the cell cap (also functioning as a negative electrode external terminal) electrically connected to an upper end of the hollow cap
53
, a current collector terminal plate
54
electrically connected to the hollow cap
53
, and an insulating plate
55
interposed between the sealing plate
51
and the current collector terminal plate
54
for electrical insulation therebetween.
The insulating gasket
52
, the insulating plate
55
, and the current collector terminal plate
54
are fixed to the sealing plate
51
by crimping the upper and lower ends of the hollow cap
53
. Spacers
56
are provided on both ends of the insulating plate
55
and molded integrally with the insulating plate
55
. The spacers
56
are disposed between the sealing plate
51
and the spirally-wound electrode body
40
to support the spirally-wound electrode body
40
for prevention of vertical loose movement. As shown in FIG.
12
(
b
), a part of the current collector terminal plate
54
is folded downward, and the negative electrode lead
33
attached to the negative electrode core body
31
is electrically connected thereto.
FIG. 13
shows the manufacturing process of this cell.
(a) The spirally-wound electrode body
40
is prepared, in which an adhesive tape is stuck at necessary positions for preventing the contact between the spirally-wound electrode body
40
and the bottom of the cell outer can
60
, and the disentanglement of the spirally-wound electrode body
40
. In FIGS.
13
(
a
) to
13
(
c
), the reference numeral
33
indicates a negative electrode lead.
(b) The negative electrode lead
33
is electrically connected to the current collector terminal plate
54
fixed to the sealing plate
51
with the sealing plate
51
of the sealing lid
50
being located above the spirally-wound electrode body
40
.
(c) The incised portion
23
formed in the portion of the exposed positive electrode core body on the outermost periphery of the spirally-wound electrode body
40
Miyazaki Noriyuki
Nakatani Kensuke
Okutani Eiji
Sugita Nobuaki
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