Zincophilic multilayer graphene structures leveraging fast and ultrastable Zn-ion storage

Abstract

The sluggish ion-migration kinetics and low accessibility of zincophilic motifs in carbon cathodes are key limitations of Zn-ion capacitors, resulting in insufficient capacitive activity and durability. The implantation of graphitized nanodomains in carbon matrixes could seemingly promote fast and stable Zn-ion storage but has not been reported yet. Herein, a multilayer graphene structure was crafted with disordered carbons by the in situ thermolysis of filter papers with the synergy of iron salt and sodium metal, triggered by graphite microcrystalline reconstitution. The carbon matrix displayed well-orchestrated graphitized nanodomains with an optimized four-layer graphene configuration, affording high-speed electron-transfer routes and more exposed electroactive sites for maximizing the charge storage. Such unique multilayer graphitized structures thus delivered fast and ultrastable Zn-ion charge storage at the structural–chemical defects, contributing to a large-current survivability (100 A g⁻¹), ultrahigh energy density (148.9 W h kg⁻¹), and extraordinary lifespan (300 000 cycles) for the assembled Zn-ion capacitors. Comprehensive investigations helped identify the source of the superb charge storage as the opposite charge-carrier-storage mechanism of the locally graphitized carbon cathodes, entailing an alternate physical uptake of Zn²⁺/CF₃SO₃⁻ at zincophilic sites and chemical interactions between the Zn²⁺ and redox-active carbonyl motifs to form Zn–O bonds. This work broadens the design space of locally graphitized carbon cathodes toward advanced Zn-based energy storage applications.