Advances in a process based on simple and environmentally compatible operations, aimed to the treatment and recycling of spent lithium-ion batteries, are reported in this paper. This process is safe, economic, and recovers as much of the battery materials as possible. It operates mainly in a selective dissolution in dilute acid, a chemical treatment of the filtrate and a thermal treatment of the solid residue. The validity of the process and its reproducibility have been evaluated at each step of the separation. This method involves very simple equipment and can be scaled-up for commercial production. Based on the projected quantities of lithium ion batteries available for recycling in the next few years, there is a significant market opportunity for a successful technology.