In this work, cobalt from spent cellular telephone Li-ion batteries was recovered by electrochemical techniques. According to X-ray diffraction results, the composition of the positive electrode is LiCoO2, Co3O4, C, and Al. The largest charge efficiency found was 96.90% at pH 5.40, potential applied of -1.00 V and a charge density of 10.0 degrees C cm(-2). The charge efficiency in the electrochemical recycling of cobalt decreases with the decrease in pH. The energy dispersive X-ray analysis (EDX) measurements of the electrodeposits showed that the surface is constituted of 100% cobalt. Scanning electron microscopy (SEM) showed a three-dimensional nucleus growth. The application of nucleation models to the initial stages of electrodeposit growth shows that at pH 5.40 electrodeposition happens with progressive nucleation. With the decrease in pH to 2.70, nucleation becomes instantaneous. (C) 2007 Elsevier B.V. All rights reserved.