RESUMO
Pendant polymers are a promising class of electrode materials due to their synthetic simplicity, derivation from sustainable feedstocks, and potentially benign synthesis. These materials consist of a redox-active pendant tethered to a polymer backbone, which mitigates dissolution during electrode cycling. To date, an extensive number of pendant groups have been studied within the context of metal-ion batteries. However, the choice of the polymer backbone and its impact on the electrode performance have been relatively understudied. In this work, we use a postpolymerization modification approach to synthesize a series of viologen-bearing redox-active pendant polymers with similar molecular weights but three distinct chemical backbones, namely, polyacrylamide, polymethacrylamide, and polystyryl. By evaluating the polymers in lithium-ion batteries, we show that the polymer backbone has a significant influence on electrode performance and behavior. Specifically, the polymethacrylamide displays slower kinetics than the other two polymers, resulting in lower capacities, particularly at high cycling rates. Furthermore, the charge storage mechanism is dependent on the nature of the backbone: the polyacrylamide shows a significant capacitive contribution to charge storage, while the polystyryl does not. The difference in performance between the polymer electrode materials is ascribed to a difference in chain mobility and packing within the electrode films. Overall, this work shows that the fundamental properties of the polymer backbone are critical to the design of high-performance polymer electrodes.
RESUMO
Thionated naphthalene diimides (NDIs) are promising materials for n-type organic semiconductors; despite their potential, synthetic routes to thionated NDIs are generally lengthy, nonselective, and low yielding and their polymeric analogues have yet to be reported in the literature. Here, we describe the rapid and selective thionation of thiophene- and selenophene-flanked NDIs using microwave irradiation and excess Lawesson's reagent. Remarkably, >99% conversion to the trans-dithionated product is observed by NMR within 45 min. Steric effects imparted by NDI core substituents prevent excess thionation, simplifying purification procedures. We apply this methodology to the postpolymerization thionation of NDI-based polymers to afford a series of polymers with varying degrees of thionation. Thionated NDIs exhibit bathochromic shifts of up to â¼100 nm in localized absorption maxima and increased electron affinities.
RESUMO
Correction for 'The rise of organic electrode materials for energy storage' by Tyler B. Schon et al., Chem. Soc. Rev., 2016, DOI: .
RESUMO
Organic electrode materials are very attractive for electrochemical energy storage devices because they can be flexible, lightweight, low cost, benign to the environment, and used in a variety of device architectures. They are not mere alternatives to more traditional energy storage materials, rather, they have the potential to lead to disruptive technologies. Although organic electrode materials for energy storage have progressed in recent years, there are still significant challenges to overcome before reaching large-scale commercialization. This review provides an overview of energy storage systems as a whole, the metrics that are used to quantify the performance of electrodes, recent strategies that have been investigated to overcome the challenges associated with organic electrode materials, and the use of computational chemistry to design and study new materials and their properties. Design strategies are examined to overcome issues with capacity/capacitance, device voltage, rate capability, and cycling stability in order to guide future work in the area. The use of low cost materials is highlighted as a direction towards commercial realization.
