Mo2TiC2Tx loaded core-shell structural MIL-88 derived iron-based cathode with in-situ Zn adulteration for high-performance aqueous zinc-ion batteries.

Abstract

New-type and high-quality cathodes are of immense importance for the development of aqueous zinc-ion batteries (AZIBs). Herein, a core-shell structural iron-based metal organic framework (MIL-88) derived cathode (ZnFe₂O₄/Fe₃O₄/C@NC/Mo₂TiC₂T_x) with admirable specific capacity, rate performance, and cycling stability has been firstly designed and prepared. The in-situ adulterated Zn and loaded Mo₂TiC₂T_x MXene could effectively modulate the electron distribution, facilitating the electron transfer from Fe and Zn to O atoms, which dramatically decrease the adsorption Gibbs energy for charge carriers and improve the electrical conductivity, leading to fast electrochemical kinetics. Moreover, the structural and chemical stability of the composites could be greatly improved by integrating MIL-88 derived doped carbon, polydopamine derived N-doped carbon coating, and MXene substrate. In addition, the unique core-shell and two dimensional/three dimensional hierarchical structure could provide plentiful active sites and optimize the charge storage kinetics. The synthesized electrode exhibits more excellent specific capacity of 467.9 mAh·g^-1 than that of Fe₃O₄/C (143.5 mAh·g^-1), Fe₃O₄/C@NC (166.4 mAh·g^-1), and ZnFe₂O₄/Fe₃O₄/C@NC (225.6 mAh·g^-1), as well as eminent rate performance and cycling stability. Additionally, the improved electrochemical performance and charge storage mechanisms of the cathode are revealed by characterizations, theoretical calculations, and simulations. The high-quality cathode and its designed strategy proposed in this study would promote the development and commercialization of AZIBs.