Cobalt-free cathodes and silicon thin-film anodes towards high-capacity solid-state batteries

This study provides a comprehensive analysis of a novel battery system, which integrates a high-loading (∼5 mAh/cm²) cobalt-free cathode composed of lithium nickel manganese aluminum oxide (LiNi_0.9Mn_0.05Al_0.05O₂, NMA) into an all-solid-state cell for the first time. The argyrodite (Li₆PS₅Cl) solid electrolyte is used in conjunction with a 99 wt% silicon thin-film anode. Room temperature discharge capacities of >210 mAh/g_NMA and > 170 mAh/g_NMA were achieved at cycling rates of 0.05C and 0.25C, respectively. Electrochemical impedance spectroscopy measurements, taken during the first cycle detail onset of electrolyte degradation, lithiation of the silicon anode, and the change in charge transfer kinetics as a function of cell voltage. Raman, Fourier Transform Infrared, and X-ray photoelectron spectroscopy are used to identify the argyrodite degradation products that form in the catholyte on cycling, unveiling lithium carbonate as a potential source of oxygen-related degradation commonly alluded to in literature. Furthermore, high cell stack pressure, 350 MPa during fabrication, led to fracturing and pulverization of some cathode particles.