Neutralization of used Li batteries: Anodic dissolution of the iron–nickel alloy positive pins of Li–SOCl₂ batteries in seawater

Abstract

This paper reports a study of the neutralization of Li–SOCl₂ batteries. Immersion of these batteries in acidic seawater solutions leads to their complete discharge by short circuit, followed by corrosion of the positive pin (made of an Fe/Ni alloy). This corrosion process is desirable because it allows penetration of water into the battery, and hence, neutralization of the active mass of the batteries through their reaction with water. The most efficient corrosion of Fe/Ni electrodes is obtained in seawater containing both HCl and H₂SO₄ in a situation of no separation between the electrode compartments, due to the reaction of the H₂ liberated at the cathode with the surface films on the anode (Fe/Ni pin electrodes). This reaction prevents passivation of the positive pin. Indeed, used Li–SOCl₂ batteries whose insulating covers were removed, corroded much quicker than regular batteries because of the impact of H₂ evolved at the case (the negative pole of the battery) on the dissolution of the positive pin.