Design of Cathode Coating Using Niobate and Phosphate Hybrid Material for Sulfide-Based Solid-State Battery

Coatingthe surface of the cathode active material of all-solid-statebatteries with sulfide-based solid electrolytes is key for improvingand enhancing the battery performance. Although lithium niobate (LiNbO3) is one of the most representative coating materials, itslow durability at a highly charged potential and high temperatureis an impediment to the realization of high-performance all-solid-statebatteries. In this study, we developed new hybrid coating materialsconsisting of lithium niobate (Li-Nb-O) and lithium phosphate (Li-P-O)and investigated the influence of the ratio of P/(Nb + P) on the durabilityperformance. The cathode half-cells, using a sulfide-based solid electrolyteLi(6)PS(5)Cl/cathode active material, LiNi0.5Co0.2Mn0.3O2, coated with the newhybrid coating materials of LiP x Nb1-x O3 (x = 0-1), were exposed to harsh conditions (60 & DEG;C and4.55 V vs Li/Li+) for 120 h as a degradation test. P substitutionresulted in higher durability and lower interfacial resistance. Inparticular, the hybrid coating with x = 0.5 performedbetter, in terms of capacity retention and interfacial resistance,than those with other compositions of niobate and phosphate. The coatedcathode active materials were analyzed using various analytical techniquessuch as scanning electron microscopy/energy-dispersive X-ray spectroscopy,transmission electron microscopy (TEM), X-ray photoelectron spectroscopy,and X-ray absorption spectroscopy (XAS) to elucidate the improvementmechanism. Moreover, the degraded cathodes were observed using time-of-flightsecondary-ion mass spectrometry, TEM/electron diffraction, and XAS.These analyses revealed that the Nb-O-P coordination in the hybridcoating material captured O by P. The coordination suppressed therelease of O from the coating layer as a decomposition side reactionto realize a higher durability than that of LiNbO3.

Automated summary

Coating the surface of all-solid-state battery cathode active material with sulfide-based solid electrolytes is crucial for enhancing battery performance. Lithium niobate (LiNbO3) is commonly used as a coating material but exhibits low durability at high charge potentials and temperatures. In this study, new hybrid coating materials of lithium niobate (Li-Nb-O) and lithium phosphate (Li-P-O) were developed, and the influence of the P/(Nb + P) ratio on durability performance was investigated. The substitution of P resulted in improved durability and lower interfacial resistance, with the hybrid coating LiP x Nb1-x O3 (x = 0.5) performing the best. Various analytical techniques were used to analyze the coated cathode active materials and reveal the mechanism behind the improved durability.