Topology-Driven Sodium Storage and Conversion in Covalent Fullerene Networks.

Abstract

Fullerene network is an emergent two-dimensional (2D) carbon allotrope in which C60 molecules are covalently bonded to form a quasi-hexagonal pattern (qHP). The intermolecular covalent bonding significantly reshapes the intrinsic electronic structure of the C60 units, leading to enhanced structural stability and electrochemical activity. Herein, we report unconventional high-density Na-ion storage and electrocatalytic conversion properties of fullerene networks (qHP-C60) driven by their covalent quasi-hexagonal topology. As an anode material for sodium-ion batteries, the covalent framework facilitates intermolecular charge transfer and creates favorable sites for Na+ adsorption, delivering a maximum reversible capacity of 279 mAh g-1 at 25 mA g-1. In addition, the interconnected and curved C60 subunits induce inhomogeneous electron distribution, accelerating the reaction kinetics of NaCl/Cl2 conversion in sodium-chlorine batteries. This enables a high current density (15,000 mA g-1 versus 1,000-1,500 mA g-1) at a significantly reduced catalyst loading amount (5 wt % versus 60-80 wt %) compared to benchmark catalysts. Our study provides insights into the covalent structural engineering of carbon materials for high-performance energy applications.