Hydrogen Reduction of LiCoO₂ Cathode Material: A Kinetic Study

Metal production is facing new challenges due to climate change and declining primary ore quality; thus, new technologies with sustainable processing routes are needed. One way to address this is to recover metals from secondary resources such as end-of-life batteries using a cleaner reducing agent hydrogen that would reduce direct carbon dioxide emissions during pyrometallurgical processing. Recycling of Li-ion battery cathode materials using hydrogen would result in a more benign metal production process and would simultaneously provide a sustainable solution to treat wastes. This study investigated the kinetics of H-2 reduction of LiCoO2 at 600-1000 degrees C up to 180 min reaction time using an isothermal mass change analysis supported with detailed microstructure evolution observations. The overall reduction mechanism appeared to follow the shrinking-core model with a different rate-limiting step depending on the reduction temperature. The activation energy of reduction at 600-800 degrees C was calculated to be 37.4 kJ/mol and was controlled by the nucleation step. The information and data obtained are useful when comparing different recycling methods and optimizing the reduction parameters of spent Li-ion battery process.