Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Patent
1995-12-21
1997-07-08
Nuzzolillo, M.
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
429176, 429247, H01M 402
Patent
active
056459610
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a zinc anode can for a battery, such can being formed into the shape of hollow cylinder with one end closed, and a manufacturing method therefor, and a manganese dry battery employing such zinc can, particularly to a technique enabling a zinc anode can of high performance and a manganese dry battery using the same without adding harmful substances such as mercury, cadmium and lead thereto. As employed herein, the term zinc anode can refers to a can-shaped member to contain an electrolyte, to form an anode of a battery, and formed of a zinc base alloy.
As is well known, a zinc anode can used for a manganese battery is manufactured through the following series of steps. and is melted therewith to form a zinc base alloy. band-shaped sheet. rolled at a temperature within a range of 200.degree.-250.degree. C. to obtain a plate-shaped sheet of a predetermined thickness. predetermined shape and dimension, such as round or hexagonal discs. form a hollow cylinder with one end closed. (Impact backward extrusion method) of the thus formed cylindrical zinc anode can.
Taking a zinc anode can for a R20 type manganese battery as an example, the thickness of the plate may be arranged to be approximately 5.2 mm at the rolling step 3. Then, round pellets of 30 mm diameter are punched out at the punching step 4, and the pellets are formed into hollow cylinders with one end closed, each having an outer diameter of 31.4 mm and thickness of 0.5 mm at the forming step 5. The height of the cylindrical can may be adjusted to 53.5 mm at the cutting step 6.
If the workability of the material for rolling or deformation processing (ductility) is not sufficient during the continuous hot rolling step 3 and the forming step 5 by the impact backward extrusion method, the material may suffer from cracks, burrs and so on, and successive working of the material will be interrupted. It is a basic and essential factor that the cylindrical cans are able to be formed at a high yield without causing defects such as cracks. (This is referred to as workability).
Finished zinc anode cans are carried to a battery assembly line, where a cathode, a separator and electrolyte are installed into the can. Then, the can is sealed with a cathode terminal and a gasket fixed to an opening of the can. When mechanical durability of the zinc can is too low at this stage, the can may be deformed during or after the battery assembly operation, thus causing various defects. Therefore, the finished zinc cans are required to have a certain mechanical strength. However, improvement in mechanical strength instead may deteriorate the above plastic workability (ductility), and vice versa.
A zinc anode can usually contacts the electrolyte contained therein in assembled batteries. Therefore, the zinc can must have sufficient corrosion resistance against the electrolyte in order to prevent self-discharge during storage of the batteries.
As required above, a zinc anode can of a battery is required to have characteristics such as plastic workability, mechanical strength after being finished as a can and corrosion resistance against the electrolyte. These characteristics relate not only to the composition of the zinc base alloy, but also to such factors of the manufacturing process as melting temperature at the melting step 1, die temperature at the molding step 2, temperature and reduction ratio at the rolling step 3, temperature at the punching step 4 for preparing pellets, temperature and workability ratio at the can forming step 5. (These factors are referred to as process factors.) Temperatures as process factors are specifically controlled to be maintained within 200.degree.-250.degree. C.
For the purpose of improving the above mentioned characteristics such as workability, mechanical strength, corrosion resistance, existing manganese batteries employ an anode formed of a zinc base alloy including approximately 0.15 wt % lead and approximately 0.05 wt % cadmium. As is well known, however, under the technical policy of
Izumi Akihide
Matsui Kazuo
Murakoshi Mitsuo
Murata Chihiro
Nakagawa Yoshiteru
FDK Corporation
Nuzzolillo M.
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