V₂O₅@ZIF-8 with a Stable Structure and a Fast Ion Diffusion Channel as a Promising Cathode Material for Lithium-Ion Batteries

The regular channels and pores of metal–organic frameworks facilitate Li diffusion and insertion, reduction of polarization, and stabilization of electrolyte–electrode interfaces in lithium-ion batteries. In this paper, a thin layer of zeolitic imidazolate framework-8 (ZIF-8) with a thickness of about 2–4 nm was decorated on the surface of V 2 O 5 by a one-step wet chemical method at room temperature. Various techniques were used to characterize the sample, including X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy coupled with energy-dispersive X-ray analysis, X-ray photoelectron spectroscopy, Brunauer–Emmett–Teller analysis, and Fourier-transform infrared spectroscopy. Cyclic voltammetry, electrochemical impedance spectroscopy, and hybrid pulse power characteristic and galvanostatic intermittent titration techniques were also used to test the electrochemical performance. The electrochemical test results showed that the capacity of V 2 O 5 @ZIF-8 was 14 and 58% higher than that of V 2 O 5 at 0.3 and 3 C, respectively, and the capacity retention of V 2 O 5 @ZIF-8 still reached 81% after 100 cycles at 0.3 C, which means better structural stability and excellent rate performance of V 2 O 5 @ZIF-8. High-speed ion channels of V 2 O 5 @ZIF-8 led to smaller polarization. The overpotential of oxidation–reduction from V 2 O 5 @ZIF-8 reduced the maximum by more than 90%. The intervention of the porous coating prevented the erosion of V 2 O 5 by the electrolyte and maintained the structure stability. This work aimed to improve the overall electrochemical performance of lithium-ion batteries and provided guidance for future research.