A Clean Closed Loop Process for Comprehensive Recovery of Valuable Components from Spent Lifepo4 Cathode Materials

Abstract

With a large number of LiFePO4 (LFP) batteries entering the retirement period, the recycling of spent LiFePO4 (S-LFP) has become a hot topic, in recent years the recovery metals from via pyro-hydrometallurgical process has been frequently reported. However, in this process more attention has been focus on selective Li extraction, the P and Fe residue after lithium extraction was not properly disposed, it causes environmental pollution and waste of valuable components. In this work, a clean closed loop method was proposed for comprehensive recovery of valuable components from spent LiFePO4 cathode materials. In this process industrial by-products (Na2SO4) as the additive is used to extraction Li, and >93.59% of the Li was selectively leached from the calcine by water immersion when a mass ratio (Na2SO4/S-LFP) of 0.95:1 at 550°C for 30 min, then the ferrophosphate slag was dissolved by dilute acid, and FePO4⋅2H2O was prepared at 90°C in acid leaching solution(pH=0.8), acid-containing leaching solution and sinking lithium mother liquor was evaporated to recover Na­2SO4 by-production and then was recycled. Compared to other pyro-hydrometallurgical process, this cleaner closed loop recycling process has the advantages of high Li leaching rate, effective recovery of P and Fe, without additional oxidants consumption and acid containing wastewater produced that conforms to the idea of green, low-carbon and sustainable development. Moreover, the oxidation roasting and selective Li extraction mechanisms were both clarified in detail, and the migration behavior of the valuable elements was also revealed.

Keywords: Spent LiFePO4, Comprehensive recovery, Waste recycling, Closed loop process