Another conventional battery technology that has been considered for EVs is Ni/Cd. Although capable of somewhat better performance than lead-acid in some respects, this battery is also more costly and does not equal the performance levels possible with advanced battery systems. It is unlikely to see widespread use in EV applications in the U.S. although there are reported to be more than 10,000 EVs using Ni/Cd batteries presently on the road in Europe . Because of the toxicity of cadmium, which precludes disposal, and the value of the nickel, there are well-developed processes for recycling of Ni/Cd batteries. Most of the facilities in Europe are dedicated Ni/Cd battery recycling plants.
The combined recycling capacity world wide was about 25,000 metric tons of Ni/Cd batteries per year in 1993, but this was significantly underutilized because of inefficient collection systems and low prices for nickel and cadmium. Both pyrometallurgical and hydrometallurgical methods are used to recycle cadmium from a variety of waste materials in plants in North America, Europe, and Japan , Cadmium is relatively easy to separate from other materials because of its low melting point and chemical activity.
Since 1995, consumer and industrial Ni/Cd battery recycling in the U.S. has been primarily done at the International Metals Reclamation Company, Inc. (INMETCO) using a process licensed from SAFT NIFE. The cadmium is distilled from the plates using a low temperature thermal process, and the material is used for new battery production. The nickel content of the battery goes into the standard INMETCO stainless steel remelt alloy production. In general, this thermal recovery process makes up the majority of the world recycling capacity. The cadmium is recovered and purified as the metal or can be converted to cadmium oxide.
Hydrometallurgical recovery processes operate on a broader variety of waste products and frequently recover other metals in addition to cadmium. They generally employ dissolution by acid treatment followed by selective extraction methods such as precipitation or ion exchange to separate the products. The economics in the hydrometallurgical case may depend on materials other than cadmium, which may not be the major species present. Cadmium recycling appears to be well developed and capacity is more than adequate to handle any near-term growth that could reasonably be expected due to growth in the EV market.
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