Metal-ion mediated mesopore engineering in hierarchical porous carbons for enhanced high-rate volumetric capacitance

Abstract

Hierarchical porous carbons (HPCs) have emerged as promising materials for energy storage, due to their ability to simultaneously deliver high capacitance and fast ion transport kinetics. However, precisely tailoring mesoporous structures of HPCs, which are critical to balance material density and capacitive performance, remains a challenge. Here, we present a scalable mesopore engineering strategy of renewable biopolymer alginate derived HPCs, enabling precise control over mesopore sizes and contents. Combining solid-state nuclear magnetic resonance, small-angle X-ray scattering, and nitrogen adsorption analyses, we unravel the "structural inheritance" mechanism of mesopore evolution from the crosslinked metal ion-alginate frameworks. The results reveal that the crosslinking degree, determined by metal ion size, governs the formation of small mesopore (ca. 5 nm) in the resulting metal-alginate derived porous carbons (metal-ADCs). Electrochemical characterizations demonstrate that these 5 nm mesopores optimize the trade-off between material density and ion transport: Cu-ADC with 25% 5 nm mesopores achieves 33 F cm -3 at 500 mV s -1 , outperforming other metal-ADCs by 20%-70%. This work uncovers the structural evolution mechanism in alginate-derived HPCs and establishes a definitive structure-performance relationship, while the scalable mesopore engineering protocol provides a transformative roadmap for designing next-generation energy storage materials with optimized volumetric performance.