中間処理プロセス・業界の現状と課題 ハイブリッドカー用電池のリサイクル技術開発

Abstract

Hybrid vehicles production is increasing year by year coping with the concern about the increase of carbon dioxide emission, and is estimated 2.5 million in 2010. Nickel metal hydride battery is mainly used for these vehicles, and 23,750t of nickel, 8,375t of rare-earth elements and 2,875t of cobalt would be contained in these batteries, in maximum, in that year. The technology development will be necessary for the recycling of these batteries at the end of use. Japan Oil, Gas and Metals National Corporation (JOGMEC) has carried out the technology development for five years, financed by Ministry of Economy, Trade and Industry (METI), Japan, to recover nickel, rare earths and cobalt from the nickel metal hydride batteries for the hybrid vehicles. The battery modules are crushed after cooling in liquid nitrogen, and separated with density, particle size and magnetism into positive and negative active materials, nickel and cobalt hydroxides and the nickel-rare earths-cobalt alloy, steel and plastics. The recovered positive active material is leached with sulfuric solution, neutralized for the selective removal of rare-earths and iron, and separated to the nickel and cobalt solutions by solvent extraction. The recovered negative active material is passed the screen or the magnetic separator for iron removal, and decarburized with hydrogen after reduction of the entrained positive active materials, to prevent from the oxidation of rare-earths. The both recovered active materials are verified to be re-usable for the battery production. The demonstration runs with capacity of one ton of battery modules a day were carried out in 2006 successfully and the high recovery rates of those metal elements were achieved.