PNNL

Abstract

High-nickel layered oxides LiNixM1-xO2 (x ? 0.9) have emerged as promising cathode materials for automotive batteries due to their high energy density and lower cost. However, the formation and accumulation of surface alkaline compounds during storage hinder their mass production and commercialization. Here, a validated chemical method is employed to deconvolute and quantify the evolution of each residual lithium compound in four representative cathodes during ambi-ent-air storage, viz., LiNiO2 (LNO), LiNi0.95Co0.05O2 (NC), LiNi0.95Mn0.05O2 (NM), and LiNi0.95Al0.05O2 (NA). Furthermore, the activation energy of reaction between water and the cathode is determined by measuring the leached LiOH concentration at various temperatures. While residual lithium and time-of-flight secondary-ion mass spectrometry measurements col-lectively reveal that the air stability overall follows the trend of NM > NA ˜ NC > LNO, the aged NM exhibits the highest charge-transfer resistance and the worst electrochemical performance among the cathodes. In situ X-ray diffraction and scanning transmission electron microscopy unveil that the aged NM is plagued by a large area of resistive spinel-like M3–xLixO4 phases, leading to aggravated particle reaction heterogeneity. Finally, a one-step recalcination method is demon-strated effective in fully restoring the degraded cathodes. This work provides insights into overcoming air sensitivity issues of high-Ni cathodes.