Deciphering the Interfacial Li-Ion Migration Kinetics of Ni-Rich Cathodes in Sulfide-Based All-Solid-State Batteries

Nickel-rich layered oxide with high reversible capacity and high working potentials is a prevailing cathode for high-energy-density all-solid-state lithium batteries (ASSLBs). However, compared to the liquid battery system, ASSLBs suffer from poor Li-ion migration kinetics, severe side reactions, and undesired formation of space charge layers, which result in restricted capacity release and limited rate capability. In this work, we reveal that the capacity loss lies in the H2–H3 phase transition period, and we propose that the inconsistent interfacial Li-ion migration is the arch-criminal. We introduce Si doping to stabilize the bulk structure and Li4SiO4 fast ionic conductor coating to regulate the interfacial behaviors between the Ni-rich cathode and sulfide-based solid electrolyte Li6PS5Cl. The modified NCM@LSO-2||LPSCl||Li–In ASSLBs deliver a high reversible capacity of 183.5 mA h g–1 at 0.1C, 30.3% higher than the bare NCM811 electrode. Besides, the interfacial regulation strategy enables the operation at a high rate of 5.0C and achieves a high capacity retention ratio of ∼85.8% after 500 cycles at 1.0C. Furthermore, the underlying mechanisms are well investigated through kinetic analyses and theoretical simulations. This work provides an in-depth understanding on the interfacial degradations between Ni-rich cathodes and sulfide-based all-solid-state electrolytes from the view of kinetic limitations and offers potential solutions.