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Nickel-metal-hydrate (NiMH) batteries are commonly used in hybrid electric vehicles such as Toyota Prius, but there are also small NiMH batteries on the market. These batteries' positive electrodes are made of nickel oxyhydroxide, while their negative electrodes utilize hydrogen stored as metal-hydrate. The electrolyte in this type of batteries are usually potassium hydroxide solutions, and the nickel oxyhydroxide reacts to form nickel hydroxide during discharge [2]. We have several toxic materials in this reaction: potassium hydroxide is an acutely poisonous substance whose ingestion can cause "severe pain, vomiting, diarrhea and collapse, while nickel hydroxide is confirmed to cause cancer in humans and animals. [3] If the chemical is left in the environment to decompose, it will release toxic gases and vapors such as nickel carbonyl. [4] Another source of concern in NiMH batteries comes from the metal alloy it uses to hold hydrogen: the most common alloy is out of rare earth material such as lanthanum nickel whose toxicity has not been thoroughly investigated, although pure lanthanum and nickel are moderately to highly toxic. This lends us sufficient reasons to remain cautious about their compound. Given the toxic material it contains, the NiMH batteries may not be perfectly benign to the environment.

Another type of popular batteries are out of lithium-ion. They are used in devices such as iPhone 4G, plug-in hybrid vehicles, and full electric vehicles by Tesla Motor. These batteries' positive electrodes are from materials that can produce lithium-ion, while the negative electrodes are from elemental lithium intercalated on graphite [5]. Lithium ions are "widely distributed in nature; trace amounts are found in many minerals, in most rocks and soils, and in many natural waters," and FDA approves the use of ionic lithium in drugs [6,7]. Similarly, neither elemental lithium nor graphite are toxic, and their combination eliminates the volatile nature of metallic lithium. The electrolyte can be made out of many materials, but LiPF6 in carbonate solvent is the most common. Lithium carbonate can be a toxin to humans and animals, while LiPF6 can react with water to produce hydrofluoric acid, which is a major pollutant and contact poison. However, considerable amount of R&D has gone into improving the electrolytes: both polymer and ceramic materials are hopeful candidate for the next generation of lithium-ion batteries. As of the moment, lithium-ion cells have the least environmental impact in the battery family.

From our quick review, the electric vehicles' batteries do not seem to be as zero impact as we would like. Unlike the lead-acid batteries in traditional motor, both NiMH and lithium-ion batteries are classified as non-hazardous except in California, where all batteries need special treatment. Because of this policy, approximately 1.15 x 105 tonnes of nickel is released to the environment as of 2008. Although this is only about one third of the 3.4 x 105 tonnes of lead lost in the environment in the same year, it may still contribute to an environmental crisis if we convert all of the vehicles in the world to electric power. [8] Therefore, it is better to remain cautious about large scale implementation of electric vehicles until we have mastered reliable ways to recycle their batteries.
 

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good find ,Stanford University reference source, Rebecca Nie 2010
i know that hybrid batteries are not he best solution but in the short term they have proven to be very useful in lowering green house emissions
Hybrid battery recycling

Toyota vehicles are amongst the most economical and environmentally friendly available and hybrid battery recycling is important to us. Removing and disposing of a hybrid battery is done by a Toyota Authorised Repairer, and, under EU Directive 2006/66/EC, we aim to recycle over 50% of the weight of a hybrid battery.
source toyota,
i also know that my fuel bill has halved making me a happy bunny :D
 

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Very interesting article on batteries. One of the great "spin offs" of electric cars is the accelerated development of battery technology which has to be a good thing.
It rubs off on so many other things that can be battery driven Eg power tools, vacuum cleaners to name but a few.
It is certainly noticeable how the lithium ion powered hand drills are so much better than say the old NiCd (nickel cadmium) batteries. They don't seem to have the "memory" problem either, as well as being much quicker to charge and more powerful.
Technology is great when it works !!!
:cool:
 
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