Robust fluorite-structured high-entropy oxides with integrated multi-active site construction for catalytic cathodes of Li–CO2 batteries

Abstract

As emerging high-energy storage devices, lithium–carbon dioxide (Li–CO₂) batteries facilitate carbon neutrality and address the current limitations of lithium-ion batteries in terms of energy density. Stable and highly active catalytic cathodes constitute a pivotal factor in driving the commercialization of Li–CO₂ batteries with regard to reactant activation and decomposition of discharge products in a timely manner. Herein, ceria-based high-entropy oxides (HEOs), denoted as CeFeCoNiMnO_x, were synthesized by exploiting the exceptional heterogeneity-tolerant properties of fluorite-structured cerium oxide (CeO₂). Leveraging the robust structural and chemical stability of the CeO₂ framework, the encapsulated polymetallic active sites within the oxide are effectively integrated, thereby enhancing the electrochemical performance of the cathode. The resultant Li–CO₂ battery demonstrates a remarkable discharge voltage at 2.98 V, a substantial discharge capacity of 11 128 mA h g⁻¹ and an exceptional cycling stability of 171 cycles based on the HEOs at a current rate of 100 mA g⁻¹. Benefiting from the effective decomposition of discharge products by the synergistic action of multiple active sites, the cell exhibits a leading low overpotential of 0.91 V. The innovative design approach for utilizing fluorite-structured CeO₂ as a substrate for the integration of multiple active sites and the subsequent construction of HEOs broadens the spectrum of catalytic cathodes for Li–CO₂ batteries.