To understand the mechanism of the reaction catalyzed by high-entropy-alloy (HEA) electrocatalysts, it has become increasingly crucial to investigate the chemical nature of the adsorbed intermediate species on the metal...

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High-entropy oxide (HEO) is an emerging type of anode material for lithium-ion batteries with excellent properties, where high-concentration oxygen vacancies can effectively enhance the diffusion coefficient of lithium ions. In this study, Ni-free spinel-type HEOs ((FeCoCrMnZn)3O4 and (FeCoCrMnMg)3O4) were prepared via ball milling, and the effects of zinc and magnesium on the concentration of oxygen vacancy (OV), lithium-ion diffusion coefficient (D Li+ ), and electrochemical performance of HEOs were investigated. Ab initio calculations show that the addition of zinc narrows down the band gap and thus improves the electrical conductivity. X-ray photoelectron spectroscopy (XPS) results show that (FeCoCrMnZn)3O4 (42.7%) and (FeCoCrMnMg)3O4 (42.5%) have high OV concentration. During charge/discharge, the OV concentration of (FeCoCrMnZn)3O4 is higher than that of (FeCoCrMnMg)3O4. The galvanostatic intermittent titration technique (GITT) results show that the D Li+ value of (FeCoCrMnZn)3O4 is higher than that of (FeCoCrMnMg)3O4 during charge and discharge. All of that can improve its specific discharge capacity and enhance its cycle stability. (FeCoCrMnZn)3O4 achieved a discharge capacity of 828.6 mAh g–1 at 2.0 A g–1 after 2000 cycles. This work provides a deep understanding of the structure and performance of HEO.

Functionalized carbon nanomaterials are potential candidates as anode materials in potassium-ion batteries (PIBs). The inevitable defect sites in architectures greatly affect the physicochemical properties of carbon nanomaterials, thus defect engineering...

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Design and fabrication of novel electrode materials with excellent specific capacitance and cycle stability are urgent for advanced energy storage devices, and the combinability of multiple modification methods is still insufficient. Herein, Ni 2+ , Zn 2+ double-cation-substitution Co carbonate hydroxide (NiZnCo-CH) nanosheets arrays were established on 3D copper with controllable morphology (3DCu@NiZnCo-CH). The selfstanding scalable dendritic copper offers a large surface area and promotes fast electron transport. The 3DCu@NiZnCo-CH electrode shows a markedly improved electrochemical performance with a high specific capacity of ∼1008 C g −1 at 1 A g −1 (3.2, 2.83, and 1.26 times larger than Co-CH, ZnCo-CH, and NiCo-CH, respectively) and outstanding rate capability (828.8 C g −1 at 20 A g −1 ) due to its compositional and structural advantages. Density functional theory (DFT) calculation results illustrate that cation doping adjusts the adsorption process and optimizes the charge transfer kinetics. Moreover, an aqueous hybrid supercapacitor based on 3DCu@NiZnCo-CH and rGO demonstrates a high energy density of 42.29 Wh kg −1 at a power density of 376.37 W kg −1 , along with superior cycling performance (retained 86.7% of the initial specific capacitance after 10,000 cycles). Impressively, these optimized 3DCu@NiZnCo-CH//rGO devices with ionic liquid can be operated stably in a large potential range of 4 V with greatly enhanced energy density and power capability (110.12 Wh kg −1 at a power density of 71.69 W kg −1 ). These findings may shed some light on the rational design of transition-metal compounds with tunable architectures by multiple modification methods for efficient energy storage.