Surface-Engineered Core–Shell CeO2@C Spheres with Controllable Oxygen Vacancies for High-Rate and Ultralong-Cycling Aqueous Zinc-Ion Batteries

Abstract

Aqueous zinc ion batteries (AZIBs) have attracted much attention due to their high safety and low cost. Electrode materials built on cerium oxides are emerging as compelling cathode options for AZIBs. These materials combine high theoretical capacity, abundant oxygen vacancy active sites, and minimal environmental impact, but their poor intrinsic electrical conductivity and rapid decay in cycling stability due to volume expansion during cycling have severely limited practical applications. Herein, a spherical CeO₂@C composite with a core–shell structure was developed through a combination of coating and controlled pyrolysis process. The uniform carbon layer encapsulation can simultaneously enhance the electronic conductivity and alleviate the bulk deformation of CeO₂@C composite. Benefit from the enhanced interfacial charge transport effect and oxygen vacancy modulation facilitated by the carbon layer, the CeO₂@C cathode delivers a capacity of 358.3 mAh g⁻¹ at 1 A g⁻¹. Moreover, the capacity retention rate of assembled AZIB with CeO₂@C cathode is as high as 65.0% after 10 000 cycles. The results of XRD and XPS spectroscopy demonstrate that the coated carbon layer effectively enhances the electrochemistry and structure stability by suppressing the irreversible Ce³⁺/Ce⁴⁺ redox variations and alleviating lattice stress induced by Zn²⁺ embedding/disembedding. This work presents a novel approach to enhance the performance of cerium-oxide cathode and presents a versatile core–shell synergistic strategy to inform the architectural design of diverse metal–oxide electrodes.