title: Cation-Dependent Stabilization of Electrogenerated Naphthalene Diimide Dianions in Porous Polymer Thin Films and Their Application to Electrical Energy Storage.
abstract: Porous polymer networks (PPNs) are attractive materials for capacitive energy storage because they offer high surface areas for increased double-layer capacitance, open structures for rapid ion transport, and redox-active moieties that enable faradaic (pseudocapacitive) energy storage. Here we demonstrate a new attractive feature of PPNs--the ability of their reduced forms (radical anions and dianions) to interact with small radii cations through synergistic interactions arising from densely packed redox-active groups, only when prepared as thin films. When naphthalene diimides (NDIs) are incorporated into PPN films, the carbonyl groups of adjacent, electrochemically generated, NDI radical anions and dianions bind strongly to K(+), Li(+), and Mg(2+), shifting the formal potentials of NDI's second reduction by 120 and 460 mV for K(+) and Li(+)-based electrolytes, respectively. In the case of Mg(2+), NDI's two redox waves coalesce into a single two-electron process with shifts of 240 and 710 mV, for the first and second reductions, respectively, increasing the energy density by over 20 % without changing the polymer backbone. In contrast, the formal reduction potentials of NDI derivatives in solution are identical for each electrolyte, and this effect has not been reported for NDI previously. This study illustrates the profound influence of the solid-state structure of a polymer on its electrochemical response, which does not simply reflect the solution-phase redox behavior of its monomers.
authors.affiliation: Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301 (USA).
authors.forename: Catherine R
authors.initials: CR
authors.lastname: DeBlase
authors.affiliation: Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301 (USA).
authors.forename: Kenneth
authors.initials: K
authors.lastname: Hernández-Burgos
authors.affiliation: Department of Chemistry and Center for NanoScience (CeNS), University of Munich (LMU), Butenandtstrasse 5-13, 81377 Munich (Germany).
authors.forename: Julian M
authors.initials: JM
authors.lastname: Rotter
authors.affiliation: Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301 (USA).
authors.forename: David J
authors.initials: DJ
authors.lastname: Fortman
authors.affiliation: Departamento de Química Orgânica e Inorgânica, Universidade Federal do Ceará, Fortaleza, CE 60455-970 (Brazil).
authors.forename: Dieric dos S
authors.initials: Ddos S
authors.lastname: Abreu
authors.affiliation: Department of Analytical Chemistry, Institute of Chemistry, Universidade Estadual de Campinas, 13083 Campinas (Brazil).
authors.forename: Ronaldo A
authors.initials: RA
authors.lastname: Timm
authors.affiliation: Departamento de Química Orgânica e Inorgânica, Universidade Federal do Ceará, Fortaleza, CE 60455-970 (Brazil).
authors.forename: Izaura C N
authors.initials: IC
authors.lastname: Diógenes
authors.affiliation: Department of Analytical Chemistry, Institute of Chemistry, Universidade Estadual de Campinas, 13083 Campinas (Brazil).
authors.forename: Lauro T
authors.initials: LT
authors.lastname: Kubota
authors.affiliation: Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301 (USA). hda1@cornell.edu.
authors.forename: Héctor D
authors.initials: HD
authors.lastname: Abruña
authors.affiliation: Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853-1301 (USA). wdichtel@cornell.edu.
authors.forename: William R
authors.initials: WR
authors.lastname: Dichtel
keywords: electrical energy storage devices; electrochemistry; porous polymers; redox processes; supercapacitors