Enhanced supercapacitor performance of high-entropy spinel oxide (AlMnFeNiTi)₃O₄ via pore structure regulation

Abstract

High-entropy spinel oxides (HEOs) have attracted increasing attention for supercapacitor applications due to their structural stability and multicomponent redox activity. However, their practical application is hindered by sluggish ion transport kinetics and limited pore accessibility. Here, we report a solution combustion method with a preliminary gelation step, using acetylene black as a sacrificial template to tailor the pore structure of (AlMnFeNiTi)₃O₄ HEOs. The introduction of 5 wt% acetylene black preserves the single-phase spinel structure while generating an interconnected hierarchical porous framework after template removal. The optimized HEO-5 %C sample exhibits the highest mesoporous contribution (65.43 %) with a mesopore volume of 0.08417 cm3 g−1, and a median pore diameter of 32.68 nm, indicating an optimized hierarchical pore structure containing interconnected mesopores and larger pores. In a three-electrode system, this material delivers 310.10 C g−1 at 1 A g−1 and retains 87 % capacity after 10,000 cycles. After long-term cycling, HEO-5 %C maintains relatively low impedance despite a moderate increase in charge-transfer resistance. A symmetric supercapacitor assembled from the material maintains a Coulombic efficiency ∼0.98 over 10,000 cycles. This work demonstrates that sacrificial templating regulates hierarchical pore topology and reduces ion transport tortuosity, thereby improving electrochemical kinetics, offering a new strategy for designing high-entropy oxide electrodes for advanced energy storage.