Alkali-enhanced polyvinylidene fluoride cracking to deeply remove aluminum impurities for regeneration of battery-grade lithium iron phosphate

Abstract

In the process of spent lithium iron phosphate resource recovery, a critical determinant in the extent of aluminum extraction is the presence of the binder. This binder encapsulates the aluminum foil, creating challenges in its removal and consequently hindering the attainment of battery-grade lithium iron phosphate (LFP) of the process. In this work, we implemented an alkali-enhanced PVDF cracking technique for efficient aluminum removal in spent LFP battery recycling. This innovative approach achieved a remarkable 98.6% aluminum removal rate, alongside a 97.8% lithium recovery rate, ensuring the production of battery-grade LFP. Notably, the recovered cathode material exhibited minimal alterations in chemical composition, crystal structure, and morphology. The results reveal that hydrogen generated during the alkali leaching reaction expands the interface between the aluminum foil and cathode material, enhancing the accessibility of OH– ions. These ions play a crucial role in decomposing the polyvinylidene fluoride (PVDF) binder and neutralizing the released HF. Moreover, OH– ions significantly aid in PVDF removal during calcination, facilitating deeper aluminum removal in subsequent processes. This research introduces a cost-effective, alkaline leaching-calcining process as a pre-treatment method for deep aluminum removal from spent cathode powders. This method not only removes impurity aluminum effectively but also ensures high lithium recovery, making the recycled product both battery-grade and economically viable at $6.06/Kg.