Optimized Purification Methods for Metallic Contaminant Removal from Directly Recycled Li-Ion Battery Cathodes

Abstract

The viability of emerging direct recycling techniques for lithium-ion battery materials relies on achieving a high-purity material output. Residual metallic contaminants in recycled cathodes are of particular concern, as they introduce significant variability in cell performance and may cause catastrophic cell failure. Thus, shredded battery materials (i.e., black mass; BM) must undergo a purification process to remove metallic contaminants. In the present work, we demonstrate optimized process conditions for the corrosion of solid impurities to ionic form using tailored alkaline chemistry, without incurring damage to the target cathode material (Li(NixMnyCo1-x-y)O2; NMC). Complete ionization of industrially relevant levels of Al and Cu impurities is achieved under conditions of mildly elevated temperature, ultrasonication, and the use of a chelating agent. Structural (XRD, SEM) and electrochemical (impedance, cycling, dQ/dV) analysis of NMC subject to treatment conditions suggests that purification method does not disrupt the cathode’s bulk physico-electrochemical properties. We have applied this purification technique to a laboratory-simulated BM and demonstrated a restoration of pristine performance. Finally, we report on our efforts to tune post-treatment conditions to ensure optimal surface structure and chemistry for subsequent direct recycling processes. Figure 1