Improving the electro-chemo-mechanical stability of nickel-rich cathodes through tungsten modification for high-performance solid-state batteries

LiNiO$_2$ represents the Co-free endmember of the layered Ni-rich oxide family and offers the highest practical capacity (energy density) among this class of cathode active materials (CAMs). However, its implementation in thiophosphate-based solid-state batteries is hampered by structural instability and interfacial degradation, particularly at high states of charge. Tungsten incorporation has been identified as a promising strategy to overcome these limitations; proven benefits include reduced particle fracture and improved capacity retention. In the present work, we systematically investigate a wetness impregnation approach applied at the precursor stage to achieve uniform tungsten distribution throughout the bulk and along the grain boundaries. Differential capacity analysis, electron microscopy, electrochemical impedance spectroscopy combined with distribution of relaxation times analysis, X-ray photoelectron spectroscopy, and in situ gas analysis collectively show that electro-chemo-mechanical degradation is mitigated during cycling. Taken together, these findings establish tungsten incorporation via precursor impregnation as an effective and scalable route to stabilizing Ni-rich cathodes, with direct implications for the development of high-performance, Co-free CAMs for solid-state battery applications.