The implementation of all-solid-state batteries (ASSBs) is regarded as an important step toward next-generation energy storage systems, in particular for electric vehicles and portable electronics. This may be achieved through application of layered Ni-rich oxide cathode materials such as Li 1+x (Ni 1−y−z Co y Mn z ) 1−x O 2 (NCM) with high specific capacity and thiophosphate-based solid electrolytes. Here, the profound effect that the secondary particle size of the cathode active material has on the capacity of ASSB cells comprising NCM622 (60% Ni), β-Li 3 PS 4 , and In anode is demonstrated. We show the benefits of using small particles (d ≪ 10 μm), allowing virtually full charge capacity. This finding is rationalized through galvanostatic charge−discharge tests and complementary ex situ and operando X-ray diffraction experiments combined with Rietveld refinement analysis. Our results indicate the importance of considering and avoiding electrochemically inactive electrode material in bulk-type ASSBs, which we show using charge transport measurements is due to poor electronic contact (in carbon-free cathode composites).

Bulk-type all-solid-state batteries (SSBs) are receiving much attention as next-generation energy storage technology with potentially improved safety and higher power and energy densities (over a wider operating temperature range) compared to conventional Li-ion batteries (LIBs). However, practical implementation of SSBs faces a number of hurdles, such as issues related to interfacial stability between the solid electrolyte (SE) and other active and inactive electrode constituents. One approach to effectively prevent or mitigate side reactions at the positive electrode is through surface coating of the cathode material with a dielectric material. In this article, we report on the preparation of Li 2 CO 3 -and Li 2 CO 3 /LiNbO 3 -coated NCM622 (60% Ni) for application in pelletized SSB cells using β-Li 3 PS 4 as the SE. Specifically, we demonstrate that in contrast to state-of-the-art LIBs, the presence of surface carbonate contaminants helps improve the cell cyclability, and the combination of carbonate and niobate species in a kind of hybrid or solid-solution coating is particularly beneficial for achieving stable performance of Ni-rich NCM composite cathodes of practical loading (91% capacity retention after 100 cycles at a C/10 rate and 25 °C). This is in part because of the formation of robust interfaces in the cathode layer, strongly suppressing CO 2 evolution (because of decomposition of the relevant carbonate species) and the accompanied SO 2 formation and release during cycling operation.

The formation of gaseous side products in liquid electrolyte-based lithium-ion batteries has been intensively studied in recent years and identified as being one of the sources of degradation (an indication of electrolyte and electrode instabilities). Herein, we demonstrate, to our knowledge for the first time, that gassing can also arise in all-solid-state battery cells made of Ni-rich layered oxide cathode materials and thiophosphate-based solid electrolytes. Combining isotopic labeling, titration for quantitative carbonate determination, and operando gas analysis, our findings reveal the evolution of CO2 stemming from carbonate species on the cathode surface as well as O2 from the bulk of the oxide cathode at potentials above 4.5 V with respect to Li+/Li, among others.

Silicon oxycarbide (SiOC) is gaining increasing attention as a promising anode material for lithium ion batteries due to its higher reversible capacity compared to incumbent graphite.