Carbon materials have beneficial properties, such as good electrical transport, high surface areas, and low density, that make them popular components in electrochemical energy storage (EES) and conversion applications. As society’s energy needs have increased requirements of EES devices, three-dimensionally (3D) continuous, nanostructured electrode materials have gained interest, as they give a pathway to 3D interconnected EES devices with high interfacial contact between electrodes over low areal footprints. In order to take advantage of such electrodes, continuous porosity should be small enough for significant surface area, but large enough to allow for efficient filling of the pore space with the separator and counter electrode through facile means, such as solution-based backfilling. Amphiphilic block copolymers (BCPs) have long been used as structure directing agents for inorganic or organic additives to make hybrid organic-inorganic, or organic-organic, nanostructured materials. These hybrids could be further processed, through means such as thermal treatment, in order to produce nanostructured functional materials, with structures typically on the order of nanometers to tens of nanometers. Ultra-large molar mass (ULMM) linear BCPs could potentially be used to access and direct structures on the difficult-to-reach length scale of 100-200 nm, however, if kinetic difficulties of these ULMM BCPs associated with a tendency to be trapped in micellized morphologies could be overcome. In this work, ULMM poly(styrene-<i>block</i>-2-dimethylaminoethyl methacrylate) (or simply SA) BCPs were synthesized and used as structure directing agents for phenol-formaldehyde resols carbon precursors. By using a carefully tuned binary solvent system guided by Hansen solubility parameters, micellization pathways present in pure solvents were avoided. Upon pyrolysis at either 900 °C or 1600 °C, hybrid SA-resols films were converted into monolithic ultra-large porous carbons (ULPCs). These ULPCs had a 3D continuous, albeit disordered, pore space with average pore sizes on the order of 100 nm after pyrolysis and subsequent carbon activation. ULPCs were characterized to elucidate structure and carbon quality.

Tuning the structure direction of resols by ultra-large molar mass linear diblock copolymers with a binary solvent system: A pathway to carbons with ultra-large, co-continuous pore spaces

ACS Spring 2022

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