Coal-Derived Mesoporous Turbostratic Graphene with Intrinsic Heteroatom Doping and Expanded Interlayer Spacing for High-Energy Lithium-Ion Capacitors

Abstract

Coal feedstock can serve as an abundant, economical, and sustainable carbon source for the development of electrode materials for advanced energy storage systems. Considerable efforts have been devoted to developing energy storage devices that bridge the performance gap between supercapacitors and batteries by simultaneously delivering high energy and high-power densities for advanced electronic applications. Lithium-ion capacitors (LICs), which integrate a battery-type anode with a capacitive carbon cathode in a high-voltage electrolyte, represent a promising architecture for achieving this balance, where efficient anode materials are critical to device performance. Herein, turbostratic graphene (T-rGO) anodes are synthesized from coal feedstock via an ultrafiltration-assisted chemi-thermal route, enabling in situ incorporation of sulfur and nitrogen from the intrinsic heteroatom content of the coal aromatic matrix without external dopants or post-synthetic treatment. The resulting T-rGO exhibits expanded interlayer spacing and hierarchical mesoporosity, facilitating rapid ion transport and enhanced charge storage. In Li-ion half-cells, T-rGO delivers a discharge specific capacity of 274 mAh g−1 at 0.1 A g−1, while Dunn’s analysis reveals a hybrid charge-storage mechanism involving both pseudocapacitive and intercalation-controlled contributions. A full-cell LIC employing a prelithiated T-rGO anode and an activated carbon cathode achieves a high energy density of 68 Wh kg−1 together with a power density of 7.5 kW kg−1 over a wide operating voltage window in the range of 1.5−4.5 V. These findings establish coal-derived turbostratic graphene as a sustainable, high-performance anode platform for future hybrid supercapacitors, with significant potential for advanced energy storage and carbon-based electronic applications.