Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Separator – retainer – spacer or materials for use therewith
Patent
1998-09-01
2000-09-26
Kalafut, Stephen
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Separator, retainer, spacer or materials for use therewith
4283191, H01M 216
Patent
active
061240591
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to porous separators which are suitable in particular for sealed lead-sulphuric acid accumulators.
In accumulators and batteries with acid electrolytes, such as for example lead-sulphuric acid accumulators, battery separators are used in order to prevent a direct contact between the oppositely charged electrode plates and suppress the occurrence of short-circuits between the plates caused by metal particles.
The separators consist of a non-conductive material which guarantees an electrolytic current transport. Battery separators should have a low electrical resistance, i.e. allow the ionic current flow to pass in as unhindered a manner as possible.
In addition, battery separators must be resistant to the chemical and physical conditions inside the battery, i.e. to oxidative and acid conditions both at ambient and at increased temperature.
For applications with a high energy and power requirement, such as e.g. in electric vehicles, there is a need for compact, maintenance-free accumulators with high capacity. The achievement of high performance levels with a compact structure requires the smallest possible distances between the electrode plates and thus the thinnest possible separators.
In recent developments of sealed lead batteries, a free electrolyte is completely dispensed with and the space between the electrode plates is completely filled by the separator. The electrolyte is absorbed by the separator. Be cause of the small distances between electrodes and the small separator thickness which these cause, materials with a high acid-absorption capacity are necessary in order to guarantee an adequate quantity of acid for the electrochemical conversion.
To ensure a uniform flow of current with this structure and prevent a drying out of the electrodes, a good contact between electrodes and separator must be guaranteed over the whole electrode surface. To achieve this, electrodes and separators are brought together under pressure. At the same time, a long battery life is guaranteed in this way, as a deficient electric contact between the lead oxide particles of the active mass of the positive electrode and between active mass and current shunt grid causes a reduction in mass utilization and thus a premature loss of capacity with a low cycle life.
With a view to a sought-after freedom from maintenance, such accumulators are usually manufactured in sealed form. This requires suitable measures for preventing the consumption of water caused by the escape of oxygen and hydrogen which can be formed during the charging process through decomposition of the water. In the ideal case, the oxygen formed at the positive electrode is completely consumed at the negative electrode and a consumption of water as a result of the charging process is thereby prevented. The transport of oxygen generally takes place through diffusion of the gaseous oxygen through the separator. For this, the separator must have open channels with a suitable pore size.
U.S. Pat. No. 3,862,861 and GB 1 364 283 disclose sealed lead accumulators which contain glass fibre mats as separators. Glass fibre separators tend to form an acid layering during the charging and discharging of the battery, i.e. layers of varying concentration within the separator, which leads to a premature capacity loss of the battery. Also, as a result of gravitational forces, a filling profile develops, i.e. a concentration of the acid in the lower part of the separator. The overall height of the battery is thereby limited and, as with the acid layering, leads to a premature capacity loss of the battery. Glass fibres break readily when the electrode plates are pressed together, which is associated with a loss of restoring force and a decrease in the pressure exerted on the plates. Because of their low elongation at break, glass fibre mats can also be processed only with difficulty. They cannot be welded and thus cannot be used as pocket separators. A particular disadvantage is that fibre mats are strongly compressible and thus display a pressure-re
REFERENCES:
patent: 4119772 (1978-10-01), Peters et al.
patent: 4298668 (1981-11-01), Schmidt et al.
patent: 5009971 (1991-04-01), Johnson et al.
patent: 5336573 (1994-08-01), Zuckerbrod et al.
patent: 5362582 (1994-11-01), Chang et al.
patent: 5720780 (1998-02-01), Liu et al.
patent: 5882721 (1999-03-01), Delnick
patent: 5928811 (1999-07-01), Khavari
patent: 5948464 (1999-09-01), Delnick
Bohnstedt Werner
Deiters Jorg
Ihmels Klaus H.
Ruhoff Jurgen
Daramic, Inc.
Kalafut Stephen
LandOfFree
Separator for sealed lead accumulators does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Separator for sealed lead accumulators, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Separator for sealed lead accumulators will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2098423