Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Electrode
Patent
1993-08-09
1997-01-14
Kalafut, Stephen
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Electrode
429185, 429238, 429245, 29 2, 4272082, 427327, H01M 470
Patent
active
055937977
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to the construction of a battery electrode plate that is resistant to chemical attack and corrosion, and provides an electrolyte-tight seal.
BACKGROUND OF THE INVENTION
Even though there has been considerable study of alternative electrochemical systems, the lead-acid battery is still the battery of choice for general purposes such as starting a vehicle, boat or airplane engine, emergency lighting, electric vehicle motive power, energy buffer storage for solar-electric energy, and field hardware, both industrial and military. These batteries may be periodically charged from a generator or other source of suitable DC power.
The conventional lead-acid battery is a multi-cell structure. Each cell generally comprises a set of vertical interdigitated monopolar positive and negative plates formed of lead or lead-alloy grids containing layers of electrochemically active pastes or active materials. The paste on the positive electrode plate when charged comprises lead dioxide (PbO.sub.2), which is the positive active material, and the negative plate contains a negative active material such as sponge lead. An acid electrolyte based on sulfuric acid is interposed between the positive and negative plates.
Lead-acid batteries are inherently heavy due to the use of the heavy metal lead in constructing the plates. Modern attempts to produce light-weight lead-acid batteries, especially in the aircraft, electric car and vehicle fields, have placed their emphasis on producing thinner plates from lighter weight materials used in place of and in combination with lead. The thinner plates allow for the use of more plates for a given volume, thus increasing the power density of a conventional lead-acid battery. However, the extent to which conventional battery performance can be improved upon is limited by its inherent construction.
Bipolar batteries are not new and have been known for some time and offer the potential for improvement over monopolar battery technology. Bipolar battery construction comprises a series of electrode plates that each contain a negative active material on one side and a positive active material on the other side, hence the terms "bipolar" and "biplate". The biplates are serially arranged in such a fashion that the positive side of one plate is directed toward the negative side of an opposing plate. The bipolar battery is made up of separate electrolytic cells that are defined by biplates of opposing polarities. The biplates must be impervious to electrolyte and be electrically conductive to provide a serial connection between cells.
The bipolar battery is characterized by having improved current flow over that of conventional monopolar batteries. The enhanced current flow is the result of through-plate current transfer from one polarity of the biplate to the other. In a conventional monopolar battery the current must travel from one electrode plate to another of opposite polarity via a conductive path which commonly is circuitous and of relatively considerable length. The significantly shortened intercell current path inherent in the bipolar battery reduces the battery's internal resistance, making it more efficient than the conventional monopolar battery in both discharging and charging modes of operation. This reduced internal resistance permits the construction of a bipolar battery that is both smaller and lighter than its equivalent monopolar battery, making it a highly desirable alternative for use in the aircraft, military and electric vehicle industry where considerations of size and weight are of major importance.
The bipolar battery, however, is not without its own difficulties and problems which, heretofore, have resisted efficient resolution and solution. A first such difficulty is related to the choice of materials for the conductive sheet used to make up the biplate. The bipolar construction in its simplest form would use lead or lead alloy for the conductive sheet and intercell partition. However, since the lead of the conductive sheet is
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patent: 2694099 (1954-11-01), Zahn
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patent: 4761356 (1988-08-01), Kobayashi et al.
patent: 4939051 (1990-07-01), Yasuda et al.
patent: 5139902 (1992-08-01), Drews et al.
Kalafut Stephen
Trojan Battery Company
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