Direct Recycling of -Li₃PS₄-Based All-Solid-State Li-Ion Batteries: Interactions of Electrode Materials and Electrolyte in a Dissolution-Based Separation Process

All-solid-state batteries (ASSB) are currently developed at high pace and show a strong potential for market introduction within the next years. Though their performance has improved considerably over the last years, investigation of their sustainability and the development of suitable recycling strategies have received less attention. However, their potential for efficient circular processes must be accessed comprehensively. In this article, the separation of the solid electrolyte beta-Li3PS4 from different lithium transition metal oxide electrode materials (LiCoO2, LiMn2O4, LiNi0.8Mn0.1Co0.1O2, LiFePO4, LiNi0.8Co0.15Al0.05O2, and Li4Ti5O12) are investigated via an approach based on the dissolution and subsequent precipitation of the thiophosphate using N-methylformamide as solvent. A combination of X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, inductively coupled plasma mass spectrometry, iodometric titration, and X-ray photoelectron spectroscopy as well as electrochemical impedance spectroscopy and electrochemical characterization is used to characterize the electrolyte and electrode materials before and after separation. Herein, it is found that the presence of electrode materials in the dissolution process can lead to significant chemical reactions. These interactions can (but most not) lead to strong alteration of the electrochemical characteristics of the individual compounds. Thus, it is shown that an efficient recovery of materials likely depends on the precise material combination within an ASSB.