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Many recycling processes have been developed for spent Li-ion batteries (LIBs), such as pyrometallurgy, hydrometallurgy, and direct recycling. For all the recycling methods, however, impurities are always introduced from the current collectors or casing materials, especially aluminum (Al), which might lead to negative effects on recovered electrode materials. Therefore, it is significant to determine the impacts of Al impurity on recovered materials. Here, the influence of the Al impurity for the synthesized LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM622) precursor and cathode is systematically studied. The cell with 0.2 at % Al impurity displays the highest reversible capacities (145.2, 130.5, and 100.3 mAh g −1 from 2, 3, and 5 C, respectively) and striking cycling capability at 2 C after 100 cycles with the highest retention capacity of 138.5 mAh g −1 . Meanwhile, the excess Al ions (5 at %) lead to the Li/Mn superlattice structure and deteriorate electrochemical performance of the synthesized NCM622 cathode.

Industrial wastes and natural mixed oxide materials were evaluated as inexpensive heterogeneous catalysts for catalytic hydrothermal liquefaction (CHTL) of food wastes. Red mud and red clay achieved biocrude carbon yields of 47.0 and 39.5% with higher heating values (HHVs) of 40.2 and 37.7 MJ kg–1, respectively, which were much greater than those without the catalyst (biocrude carbon yield of 19.7% and HHV of 36.1 MJ kg–1). Biocrude characterization revealed that similar families of molecules were formed in the presence and absence of catalysts, implying that the main role of the catalyst is to promote rates of thermal reactions, leading to biocrude production without opening new pathways. The crystalline structures of inexpensive mixed oxides were stable under hydrothermal conditions, with modest calcium leaching (7.5%) and trace leaching of other metals. Using red clay or red mud resulted in >40% recovery of the energy in food waste as biocrude, greater than that obtained under noncatalytic conditions (18%) or from any individual constituent oxide (19–27%). The improved CHTL performance of the mixed metal oxides compared with single-metal oxides was attributed to the synergistic effects of base and acid sites present on catalyst surfaces; mixed oxides presented balanced densities of acids and bases, whereas the constituent oxides were either primarily acidic or primarily basic. The percent of energy recovered as biocrude oil was strongly correlated with the base-to-acid site density ratio, providing an important performance predictor for CHTL conversion of food waste to bioenergy.

Nickel (Ni)-impregnated metal oxide catalysts, Ni/CeZrOx, Ni/ZrO2, and Ni/CeO2, were investigated to maximize energy recovery and reduce char yield during catalytic hydrothermal liquefaction (CHTL) of food waste.