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A Summary of Rechargeable Battery Chemistries
When the French scientist, Gaston Plante, invented the lead-acid battery in 1859, he could not have envisioned the critical role his creation would play today in transportation, communication, electric utilities and as emergency backup systems. Without them, 21st century life would not be possible.
The development of more and more battery-powered devices and applications has fueled demand for new and different battery chemistries. Researchers have been looking for a chemistry that is at once powerful, long-lived, safe, inexpensive, lightweight and recyclable.
Following is a brief summary of lead-acid and alternate battery chemistries and their advantages and disadvantages.
Lead-acid
Advantages:
This chemistry has been proven over more than 140 years. Batteries of all shapes and sizes, available in sealed and maintenance-free products, are mass-produced today. In their price range, lead-acid batteries provide the greatest energy density (the amount of energy produced) per pound, have the longest life cycle and a large environmental advantage in that they are recycled at an extraordinarily high rate. (Ninety-seven percent of the lead is recycled and reused in new batteries.). No other chemistry can touch the infrastructure that exists for collecting, transporting and recycling lead-acid batteries.
Disadvantages:
Lead is heavier than other metals and can be toxic.
Aluminum-air
Advantages:
This is a mechanically rechargeable primary battery system with a capacity equal to 15-20 cycles on a lead-acid system (a cycle refers to a discharge and a charge).
Disadvantages:
Its components must be replaced frequently, water must be added and sludge must be removed. When combined with the expense of reprocessing aluminum, the system is nowhere near commercialization.
Lithium-ion
Advantages:
It has a high specific energy (the number of hours of operation for a given weight) making it a huge success for mobile applications such as phones and notebook computers.
Disadvantages:
More expensive than lead. The cost differential is not as apparent with small batteries for phones and computers, and owners of these devices may not realize that they are paying much more per stored kilowatt hour than other chemistries. However, because automotive batteries are larger, the cost becomes more significant. In addition, currently there is no established system for recycling large lithium-ion batteries.
Nickel-Cadmium
Advantages:
This chemistry is reliable, can operate in a range of temperatures, tolerates abuse well and performs well after long periods of storage.
Disadvantages:
It is three to five times more expensive than lead-acid, its materials are toxic and the recycling infrastructure for larger nickel-cadmium batteries is very limited.
Nickel-metal hydride
Advantages:
It is reliable and lightweight. In hybrid vehicles, these batteries are projected to have very long cycle life, equal to 100,000 miles.
Disadvantages:
The metals in the battery are 25 times more expensive than lead. Nickel has been identified as a carcinogen. Hybrid vehicles have not been on the road long enough to allow the batteries to prove their projected cycle life. No significant recycling capability exists.
Note: The Advanced Lead-Acid Battery Consortium has developed a lead-acid battery system that operates at the very high rates necessary for a hybrid vehicle and recently equipped a Honda Insight with this sytem. If it proves to be capable of reasonable life, the lead-acid batteries will challenge the very expensive nickel metal hydride system in hybrid vehicles today.
Nickel-zinc
Advantages:
This chemistry has good energy density, good operating temperature range and performs reasonably well after long periods of storage.
Disadvantages:
It is expensive and its life cycle, while improved during the past few years, is still merely adequate. So there has been no breakthrough in this chemistry.
Sodium-sulfur
Advantages:
This chemistry is about as efficient as lead-acid, but has three to four times more specific energy (the number of hours of operation for a given weight).
Disadvantages:
Twenty seven years of research has yielded only one commercial application – load leveling by electric utilities in Japan.
