Composite Electrode (LiNi_0.6Mn_0.2Co_0.2O₂) Engineering for Thiophosphate Solid-State Batteries: Morphological Evolution and Electrochemical Properties

Solid-state batteries using thiophosphate solid electrolytes are believed to be the next generation solid electrolyte batteries, but they suffer from several issues, including also the engineering of the composite positive electrode. To date, the relationship between the morphology of the composite electrode and its electrochemical performance remains undetermined. By using Focused Ion Beam–Scanning Electron Microscopy (FIB-SEM) tomography, we investigated the engineering of several composite electrodes of polycrystalline NMC 622 (LiNi 0.6 Mn 0.2 Co 0.2 O 2 ) particles and amorphous Li 3 PS 4 solid electrolyte. Based on the morphological analysis of the electronic and ionic networks, it is possible to determine that the electrochemical performance limitation in this cell emerges from the surface contact between the NMC and the LPS as the sintering of the solid electrolyte (SE) is far from optimal. Additionally, similar analyses performed after the first charge show that the fading of the electrochemical is linked to the morphological evolution in the composite positive electrode.