Dual‐Ion Intercalation and High Volumetric Capacitance in a Two‐Dimensional Non‐Porous Coordination Polymer

Abstract

Intercalation is apromising ion-sorption mechanism for enhancing the energy density of electrochemical capacitors (ECs) because it offers enhanced access to the electrochemical surface area. It requires arapid transport of ions in and out of ah ost material, and it must occur without phase transformations.M aterials that fulfil these requirements are rare;t hose that do intercalate almost exclusively cations.Herein, we show that Ni 3 (benzenehexathiol) (Ni 3 BHT), an on-porous twodimensional (2D) layered coordination polymer (CP), intercalates both cations and anions with av ariety of charges. Whereas cation intercalation is pseudocapacitive,a nions intercalate in ap urely capacitive fashion. The excellent EC performance of Ni 3 BHT provides ag eneral basis for investigating similar dual-ion intercalation mechanisms in the large family of non-porous 2D CPs.

Enhanced Redox Storage and Diverse Intercalation in Layered Metal Organic Frameworks with a Staggered Stacking Mode

“…Moreover, prior reports on intercalation in 2D van der Waals materials describe that, in addition to the intercalating cations themselves, both the nature of cation solvation and the solvent-electrode interactions also influence the interlayer spacing. 24,25,38,39 Overall, a notable expansion of the lattice under polarization, albeit incommensurate with cation size, suggests collective intercalation of both cations and protons in Ni 6 HHTT 3 .…”

“…Eclipse and slip-stacked modes create open one-dimensional (1D) pores that are explored as highly advantageous for rapid ion transport and sorption. , For instance, electrochemical capacitors using 2D MOFs based on 2,3,6,7,10,11-hexaiminotriphenylene (HITP), − 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP), − hexaaminobenzene (HAB), − and phthalocyanine , deliver greater capacitances than activated carbons. On the other hand, staggered mode reduces or, in some cases, eliminates porosity, rendering such 2D MOFs as nonporous and less attractive for capacitive charge storage. , Notably, these nonporous MOFs, which are similar to other 2D van der Waals materials − in their layered structures, offer a possibility for intercalation-based enhanced charge storage. − Moreover, an observation of intercalation in these nonporous MOFs can enable synthesis of unique intercalation compounds with honeycomb-like lattices, opening frontiers for evaluation of electronic properties in intercalation compounds beyond those based on graphite and transition-metal dichaclogenides. , However, because staggering causes partial loss of π–π interactions, 2D MOFs with such a stacking mode are uncommon, and investigations into their electrochemical behavior are rare.…”