Design and fabrication of high-entropy oxide anchored on graphene for boosting kinetic performance and energy storage

Abstract The rock salt structure of high entropy oxide (HEO) (Mg0.2Co0.2Ni0.2Cu0.2Zn0.2)O has promising prospects for energy materials. Here, we prepare HEO and calculate the entropy value S m i x ≥ 1.5R (R represents the gas constant), thus proving that HEO is obtained. In addition, we design and obtain HEO@G (HEO@Graphene) through the surface modification of HEO with graphene, which is analysed by X-ray diffraction, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy to reveal the rock salt structure of HEO@G and the formation of a planar layer architecture on the surface of HEO by graphene. The electrode well design with HEO@G as the anode material for lithium-ion batteries provides a high capacity of 1225 mA h g−1 in the first discharge at 100 mA g−1 and maintains a discharge capacity of ∼950 mA h g−1 after 200 cycles. A reversible cycling capacity of 460 mA h g−1 is obtained under the condition of multiple cycles at high speed. In terms of expansion, electrochemical impedance spectrometry and pseudocapacitance investigations deeply demonstrate that the addition of graphene enhances the diffusion dissemination coefficient of lithium ions in the composite electrode and changes the electrochemical kinetic properties of the composite anode. Such a modification approach for HEO will provide a reference in energy storage applications.