Hybrid Car Batteries, Comparing NiMH and Lithium Ion Performance, Toxicity, and Recycling

After a growing call for environmental responsibility by the car-buying public, the auto industry is employing a number of non-lead battery alternatives in hybrid vehicles. Starting off slowly, hybrid vehicle sales have now topped the one million mark, with some of the older hybrid models' batteries in need of replacement. To accommodate for the number of hybrid vehicle batteries being disposed of in the near future, auto makers are developing recycling technology today. Not only will a fully operational recycling infrastructure be in place, but less toxic battery materials will be employed.

NiMH, or nickel metal hydride
The battery type most commonly used in hybrids, with a lower toxicity than lead, NiMH batteries will last a few years beyond their 8-10 year warranty before they fail. Toyota and Honda reclaim nearly 100 percent of their batteries' plastic, metal plates, cases, and wiring. In fact, Toyota, in an effort to reduce the number of its batteries ending up in land fills, offers a $200 return for every battery it receives.

Lithium-ion - available in limited numbers later this year
Panasonic EV Energy Co., which is jointly owned by Toyota and Panasonic Corp. is increasing production to meet the increased demand for hybrid car technology, especially the Toyota Prius in recent months. Their research department is working diligently to overcome the risk of overheating which resulted in the recall of millions of laptop computers from a few years ago.

Conserving Natural Resources by Increasing Energy Density
A measure of the efficiency of batteries is calculated in their energy to weight ratio or energy density, which is especially high in lithium ion batteries. The first plug-in electric car to ship with a Li-ion battery will be the Tesla Roadster which is due out this month. The weight savings and the energy density of the Li-ion battery over a comparable NiMH one is best exemplified by the fact that the Tesla would require a 1,000-Kg NiMH battery to replace the 400-Kg Li-ion currently standard in the Roadster.

Microprocessors, logic circuitry and sensors monitor and adjust current flow within the battery to virtually eliminate the risk of overheating and explosion. Passive design features of the battery protect it from damage due to collision or penetration by foreign object. The design also prevents anyone from accessing the high voltage connections within the battery. The U.S. Department of Transportation has also performed crush, vibration and collision testing to permit the battery from being installed in vehicles.

Latest Research - Carbon Nanotube Batteries
Carbon nanotubes have been the subject of extensive research in which numerous potential applications are being explored. Chinese researchers at the Shenyang National Laboratory for Materials Science discovered that by coating the anode of a lithium ion battery with a nanotube membrane, they could extend the storage life and discharge capacity of the battery while decreasing the occurrence of overheating. The research points to the possibility of recharging lithium ion batteries in minutes, extending their life indefinitely, and cutting the cost of hybrid vehicles.

A Scarcity of Natural Resources
The availability of Lithium and the other raw materials required to manufacture Lithium-ion batteries is the subject of continued study by the Department of Energy. In a paper presented to the DOE by Argonne National Laboratory in May, 2009, the authors have concluded that the projected need for Lithium for Lithium-ion batteries in the U.S. will exceed world production levels at 25,000 tons by 2030. If fastidious recycling of spent batteries is carried out, the study also predicts that this need will never exceed world production. While Lithium use in manufacturing batteries only accounts for about 25 percent of the total industrial use, that percentage will rise.