MnO2@CeO2 composite cathode for aqueous zinc-ion batteries: enhanced electrical conductivity and stability through Mn–O–Ce bonds

Abstract

MnO₂ cathodes have been limited in rechargeable aqueous Zn-ion batteries (AZIBs), primarily due to their poor electrical conductivity and manganese dissolution. To alleviate these challenges, a critical modification is proposed to form novel Mn–O–Ce bonds by compositing MnO₂ with CeO₂. In this work, the MnO₂@CeO₂ composite cathode was synthesized via a hydrothermal reaction and annealing treatment. Wherein, the density functional theory (DFT) calculations reveal that the Mn–O–Ce bond improves the cycling stability of MnO₂@CeO₂ by mitigating the dissolution of the manganese base. Meanwhile, based on the experimental results, incorporating CeO₂ with MnO₂ not only endows the metal oxides with outstanding electrochemical performance, but also enhances their electron transfer ability by the d-orbital interaction at the Fermi level. Moreover, the detailed ex situ characterization studies, reaction kinetics analyses and DFT calculations further illustrate the performance enhancement mechanism of the MnO₂@CeO₂ composite cathode, which possesses a special urchin-like morphology and Mn–O–Ce bonds, delivering a myriad of active reaction sites, stable crystal structures, and impressive ion diffusion characteristics for the intercalation of H⁺/Zn²⁺. The optimized Zn//MnO₂@CeO₂ battery achieves an ultrahigh capacity of 355 mA h g⁻¹ at 1 A g⁻¹ and superior durability of 89.68% after 1000 continuous cycles at 1 A g⁻¹. The above results imply that the MnO₂@CeO₂ composite is a potential cathode for AZIBs, which may shed new light on further exploration in cathode materials.