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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 H2 reduction of LiCoO2 at 600–1000 °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 °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. [ABSTRACT FROM AUTHOR]

Hydrogen is an alternative reductant to replace carbon for the production of metals. Reduction by hydrogen has advantages compared to carbothermic reduction, such as faster reaction rate and cleaner by-product (water vapor). This study investigated the application of hydrogen reduction for recycling and recovering cobalt and lithium from Li-ion battery cathode material (LiCoO2). The study consisted of thermodynamic simulations of the reactions and microstructure evolution analysis from experimental work to propose mechanisms of the reduction process. The thermodynamic assessment predicted that metallic Co could be generated from 400 °C and was stable up to 1200 °C, but strongly dependent on the molar amount of H2. The final experimental reduction products of lithium and cobalt were found to vary and consisted of Li2O, LiOH, Li2O2 and Co, CoO, Co3O4, respectively. The experimental work revealed that the overall reduction mechanism is uniquely characterized by the reduction temperature. The temperature range of 800 °C to 900 °C offered more benefit as Co could be generated as a larger mass indicating a more progressive reduction. The data and information obtained can help optimize the parameters in the recycling of Li-ion batteries. [ABSTRACT FROM AUTHOR]

Recycling of Li-ion battery cathode materials using carbon from the anode materials via carbothermic reduction would provide a reduction process option that could be carried out without introducing any external reactants. From this basis, this study investigated and examined the kinetics of carbothermic reduction of LiCoO2 at 700 °C to 1100 °C under inert atmosphere up to 240 minutes reaction time using an isothermal mass change analysis combined with detailed microstructure evolution observation. The overall reduction mechanism appeared to involve diffusion of oxygen in LiCoO2 during its thermal decomposition in the first stage, followed by the nucleation of cobalt in the second stage. The activation energy of the diffusion and nucleation stages were calculated to be 121 and 95 kJ/mol, respectively. The microstructure analyses showed a complex evolution of phases. At 700 °C to 900 °C, Li2CO3 and Co phases were observed as the product of the reductions; while at 1000 °C to 1100 °C, Li2O and Co phases were observed. The information and data obtained are useful when comparing different recycling methods and optimizing the carbothermic reduction parameters for recycling cathode materials from spent Li-ion batteries. [ABSTRACT FROM AUTHOR]

When considering the extraction of metals from lunar regolith for use in space, one reductive method of interest is vacuum thermal dissociation. Given the high vacuum environment on the Moon, the sub-liquidus operation of such a process, i.e., sublimation, warrants investigation. In the current work, the kinetics of the vacuum sublimation of the more volatile major oxides found in the lunar regolith, Na2O, K2O, and FeO, are evaluated. Two distinct factors are accounted for in the current work: the change in the evaporation flux due to temperature; and the reduction in available surface area for evaporation due to sintering of the feedstock. Surface area change due to the sintering of compressed LMS-1 regolith simulant pellets was quantified via a Brunauer–Emmett–Teller analysis. The surface area of the samples was measured to vary from 3.29 m2/g in the unsintered sample, to 1.04 m2/g in the samples sintered at 800 °C, and down to 0.09 m2/g in the sample sintered at 1150 °C. Evaporation flux was calculated using the Hertz–Knudsen–Langmuir equation using saturated vapor pressures predicted from the FactSage thermochemical package and verified against Knudsen Effusion Mass Spectroscopy data from tests conducted on lunar regolith sample #12022. The combination of these studies resulted in the conclusion that no local maxima in evaporation rate below the melting point was found for the current system, as such the highest rate of sublimation was determined to be 1200 °C for all species, at temperatures of 1200 °C and above, partial melting of the material occurs. The predicted maximum rate of sublimation for the species Fe, Na, and K at 1200 °C was 0.08, 1.38, and 1.02 g/h/g of regolith, respectively. It is noted that significant variation was seen between FactSage predictions of saturated vapor pressures and the measured values. Future work generating detailed thermochemical databases to predict the behavior of complex systems similar in composition to lunar regolith would benefit the accuracy of similar kinetic studies in the future. [ABSTRACT FROM AUTHOR]