Topology-Dependent Pseudocapacitance of Ion Insertion in Zeolite-Templated Carbons

Abstract

Carbonaceous materials with uniform pore structures and tunable π-stacking provide ideal models for understanding ion storage mechanisms. Zeolite-templated carbons (ZTCs) are high-fidelity topological replicates of ordered microporous zeolites, exhibiting a framework connectivity determined by the pore connectivity of the original zeolite template. In this study, the ion storage properties of a 2D ZTC synthesized from IWV zeolite were compared to those of a 3D ZTC synthesized from FAU zeolite, to better understand ion storage mechanisms in contrasting material topologies. The 2D ZTC comprises π-stacked graphene-like sheets with an ordered array of ∼0.7 nm pores, while the 3D ZTC contains ∼1.2 nm pores with ordered, continuous 3D connectivity and no π-stacking. Electrochemical insertion of Li+, Na+, and K+ into these model porous carbons revealed the effects of pore structure and π-stacking on ion diffusion/resistance behavior. While the 3D ZTC with self-standing microporosity exhibits excellent ion storage capacity and kinetics for Li+, the unique structure of the 2D ZTC permits rapid, high-density storage of Na+ and K+ via pseudocapacitance. To synergistically harness the benefits of both ZTCs, an asymmetrical dual-ion hybrid capacitor (DIHC) for NaPF6 storage is presented, achieving up to 72 Wh kg−1 and up to 9.9 kW kg−1 at the device level, representing a unique type of energy storage device whose potential is based entirely on the network topology of the covalent carbon−carbon bonding.