The development of highly efficient catalysts in the cathodes of rechargeable Li−O 2 batteries is a considerable challenge. Polyelemental catalysts consisting of two or more kinds of hybridized catalysts are particularly interesting because the combination of the electrochemical properties of each catalyst component can significantly facilitate oxygen evolution and oxygen reduction reactions. Despite the recent advances that have been made in this field, the number of elements in the catalysts has been largely limited to two metals. In this study, we demonstrate the electrochemical behavior of Li−O 2 batteries containing a wide range of catalytic element combinations. Fourteen different combinations with single, binary, ternary, and quaternary combinations of Pt, Pd, Au, and Ru were prepared on carbon nanofibers (CNFs) via a joule heating route. Importantly, the Li−O 2 battery performance could be significantly improved when using a polyelemental catalyst with four elements. The cathode containing quaternary nanoparticles (Pt−Pd−Au−Ru) exhibited a reduced overpotential (0.45 V) and a high discharge capacity based on total cathode weight at 9130 mAh g −1 , which was ∼3 times higher than that of the pristine CNF electrode. This superior electrochemical performance is be attributed to an increased catalytic activity associated with an enhanced O 2 adsorbability by the quaternary nanoparticles.

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Nanocomposites of crystalline-controlled TiO(2) -carbon are prepared by a novel one-step approach and applied in anodes of lithium ion batteries. In our nanocomposite anodes, the Li(+) capacity contribution from the TiO(2) phase was enormous, above 400 mAh g(-1) (Li(1+x) TiO(2) , x>0.2), and the volumetric capacity was as high as 877 mAh cm(-3) with full voltage utilization to 0 V versus Li/Li(+) , which resulted in higher energy density than that of state-of-the-art titania anodes. For the first time, it was clearly revealed that the capacity at 1.2 and 2.0 V corresponded to Li(+) storage at amorphous and crystalline TiO(2) , respectively. Furthermore, improvements in the rate capability and cycle performance were observed; this was attributed to resistance reduction induced by higher electrical/Li(+) conduction and faster Li(+) diffusion.

The rechargeable Li–CO2 battery has attracted considerable attention in recent years because of its carbon dioxide (CO2) utilization and because it represents a practical Li–air battery. As with other battery systems such as the Li-ion, Li–O2, and Li–S battery systems, understanding the reaction pathway is the first step to achieving high battery performance because the performance is strongly affected by reaction intermediates. Despite intensive efforts in this area, the effect of material parameters (e.g., the electrolyte, the cathode, and the catalyst) on the reaction pathway in Li–CO2 batteries is not yet fully understood. Here, we show for the first time that the discharge reaction pathway of a Li–CO2 battery composed of graphene nanoplatelets/beta phase of molybdenum carbide (GNPs/β-Mo2C) is strongly influenced by the dielectric constant of its electrolyte. Calculations using the continuum solvents model show that the energy of adsorption of oxalate (C2O4 2–) onto Mo2C under the low-dielectric electrolyte tetraethylene glycol dimethyl ether is lower than that under the high-dielectric electrolyte N,N-dimethylacetamide (DMA), indicating that the electrolyte plays a critical role in determining the reaction pathway. The experimental results show that under the high-dielectric DMA electrolyte, the formation of lithium carbonate (Li2CO3) as a discharge product is favorable because of the instability of the oxalate species, confirming that the dielectric properties of the electrolyte play an important role in the formation of the discharge product. The resulting Li–CO2 battery exhibits improved battery performance, including a reduced overpotential and a remarkable discharge capacity as high as 14,000 mA h g–1 because of its lower internal resistance. We believe that this work provides insights for the design of Li–CO2 batteries with enhanced performance for practical Li–air battery applications.