Regulation of Oxygen Vacancies in High Entropy Oxides With Multi-Layer Eggshell Architectural Framework for Boosting the Electrochemical Performance of Supercapacitors

Abstract

High-entropy oxides (HEOs) exhibit great potential as supercapacitor electrode materials, but their practical application is hindered by inherent challenges such as structural instability, insufficient conductivity, and difficulties in regulating oxygen vacancies. To overcome these limitations, we present a dual-defect engineering strategy: tailoring the elemental composition of FeZnCuCoNi-based HEOs to generate abundant oxygen vacancies, and constructing a hierarchical, 3D multi-shell porous network structure via an in situ template method. Density functional theory calculations reveal that high-entropy lattice distortion significantly enhances oxygen vacancy concentration while reducing charge transfer barriers. Additionally, the multi-layered eggshell morphology creates interconnected ion diffusion pathways, shortens ion transport distances, and reinforces mechanical integrity. The optimized HEO electrode demonstrates remarkable electrochemical performance, achieving a specific capacitance of 641 F g⁻¹ at 1 A g⁻¹, with a 92% electric double-layer contribution at 50 mV s⁻¹. The assembled asymmetric supercapacitor delivers an energy density of 36.7 Wh kg⁻¹ at a power density of 800 W kg⁻¹, while maintaining 92% of its initial capacity after 10 000 charge–discharge cycles. Mechanistic studies indicate that oxygen vacancies optimize hydroxyl adsorption kinetics, facilitating surface charge transfer, while the hierarchical porous structure effectively mitigates volumetric expansion stress via a 3D ion transport network. This work offers a strategic framework for designing next-generation high-entropy energy storage materials by providing a synergy between atomic-scale electronic tuning and mesoscale structure design.

Keywords

high-entropy oxides / multi-layered eggshell structures / oxygen vacancies / supercapacitors

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