Dissolution and Recrystallization Behavior of Li<sub>3</sub>PS<sub>4</sub> in Different Organic Solvents with a Focus on <i>N</i>-Methylformamide
Kerstin Wissel, Luise M. Riegger, Christian Schneider, Aamir Iqbal Waidha, Theodosios Famprikis, Yuji Ikeda, Blazej Grabowski, Robert E. Dinnebier, Bettina V. Lotsch, Jürgen Janek, Wolfgang Ensinger, Oliver Clemens
Abstract
Solid-state batteries can be built based on thiophosphate electrolytes such as β-Li 3 PS 4 . For the preparation of these solid electrolytes, various solvent-based routes have been reported. For recycling of end-of-life solid-state batteries based on such thiophosphates, we consider the development of dissolution and recrystallization strategies for the recovery of the model compound β-Li 3 PS 4 . We show that recrystallization can only be performed in polar, slightly protic solvents such as N -methylformamide (NMF). The recrystallization is comprehensively studied, showing that it proceeds via an intermediate phase with composition Li 3 PS 4 ·2NMF, which is structurally characterized. This phase has a high resistivity for the transport of lithium ions and must be removed in order to obtain a recrystallized product with a conductivity similar to the pristine material. Moreover, the recrystallization from solution results in an increase of the amorphous phase fraction next to crystalline β-Li 3 PS 4 .