Structural evolution engineering of BiOBr enables diffusion-controlled charge storage for high-performance asymmetric supercapacitors

초록

Decoupling and optimizing ion transport and charge storage within a single-component electrode remains a critical limitation in electrochemical energy storage. Herein, we introduce a kinetics-driven intrinsic structure engineering strategy to regulate the nanoscale architecture of bismuth oxybromide (BiOBr) via controlled hydrothermal synthesis, eliminating the need for compositional modification or defect induction. By systematically tuning the reaction time (5–15 h), the growth pathway is directed from disordered nanosheet assemblies to a structurally optimized interconnected network, followed by overgrowth-induced densification. This enables direct establishment of a structure–kinetics–performance relationship. The optimized BiOBr-10 electrode exhibits a balanced architecture that promotes electrolyte accessibility while preserving efficient electron transport pathways, leading to enhanced electrochemical utilization. It delivers a high areal capacitance of 6.175 F/cm2 at 8 mA/cm2 with good rate capability (62.75% retention at 50 mA/cm2). Kinetic analysis (b ≈ 0.44) confirms a diffusion-governed charge storage mechanism, indicating effective bulk redox participation. The electrode maintains 85.16% capacitance retention over 15,000 cycles, demonstrating structural robustness. An asymmetric supercapacitor (BiOBr-10//AC) achieves an energy density of 0.263 mWh/cm2 at a power density of 4.5 mW/cm2, retaining 86.4% performance after 10,000 cycles. This work highlights intrinsic structural modulation as a scalable and reproducible pathway for advancing layered electrodes toward high-performance energy storage systems. © 2026 Published by Elsevier B.V.

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