RESUMEN
Solid-state batteries (SSBs) are promising candidates to significantly exceed the energy densities of today's state-of-the-art technology, lithium-ion batteries (LIBs). To enable this advancement, optimizing the solid electrolyte (SE) is the key. ß-Li3 PS4 (ß-LPS) is the most studied member of the Li2 S-P2 S5 family, offering promising properties for implementation in electric vehicles. In this work, the microstructure of this SE and how it influences the electrochemical performance are systematically investigated. To figure this out, four batches of ß-LPS electrolyte with different particle size, shape, and porosity are investigated in detail. It is found that differences in pellet porosities mostly originate from single-particle intrinsic features and less from interparticle voids. Surprisingly, the ß-LPS electrolyte pellets with the highest porosity and larger particle size not only show the highest ionic conductivity (up to 0.049 mS cm-1 at RT), but also the most stable cycling performance in symmetrical Li cells. This behavior is traced back to the grain boundary resistance. Larger SE particles seem to be more attractive, as their grain boundary contribution is lower than that of denser pellets prepared using smaller ß-LPS particles.
RESUMEN
All-solid-state batteries (ASSBs) present a promising route toward safe and high-power battery systems in order to meet the future demands in the consumer and automotive market. Composite cathodes are one way to boost the energy density of ASSBs compared to thin-film configurations. In this manuscript, we investigate composites consisting of ß-Li3PS4 (ß-LPS) solid electrolyte and high-energy Li(Ni0.6Mn0.2Co0.2)O2 (NMC622). The fabricated cells show a good cycle life with a satisfactory capacity retention. Still, the cathode utilization is below the values reported in the literature for systems with liquid electrolytes. The common understanding is that interface processes between the active material and solid electrolyte are responsible for the reduced performance. In order to throw some light on this topic, we perform 3D microstructure-resolved simulations on virtual samples obtained via X-ray tomography. Through this approach, we are able to correlate the composite microstructure with electrode performance and impedance. We identify the low electronic conductivity in the fully lithiated NMC622 as material inherent restriction preventing high cathode utilization. Moreover, we find that geometrical properties and morphological changes of the microstructure interact with the internal and external interfaces, significantly affecting the capacity retention at higher currents.
