A Viologen Polymer and a Compact Ferrocene: Comparison of Solution Viscosities and Their Performance in a Redox Flow Battery with a Size Exclusion Membrane

Abstract

In this work, the synthesis and characterization of a compact, ferrocene tetramer and a linear viologen polymer is reported. The latter material is a new, 4,4′-bipyridine containing, organo-soluble polymer. As aimed for solubility in nonpolar solvents, a 2-ethylhexyl-moiety to promote organosolubility and 4-vinylbenzyl serving as a polymerizable group are introduced to a 4,4′-bipyridine. The halide anions of the monomer cation are exchanged to bis(trifluoromethansulfon)imide, which further enhances organosolubility. The monomer is subsequently copolymerized with styrene by free radical polymerization. In addition, a four-ferrocene-containing compact structure, based on pentaerythritol, is synthesized via the straightforward radical thiol-ene reaction. The polymer solutions are thoroughly characterized hydrodynamically. Subsequently, propylene carbonate-based solutions of both materials are prepared to allow an assessment for future energy storage applications. This is done by testing battery characteristics in a custom-made flow-cell with a simple dialysis membrane for physical separation of the active materials. The capability of energy storage is verified by leaving the charged materials in solution in an open circuit for 24 h. Here, more than 99% of the stored charges can be recovered. Cycling the battery for 100 times reveals the remarkable stability of the materials of only 0.2% capacity loss per day in the battery setup.

Direct Conversion of Phase‐Transition Entropy into Electrochemical Thermopower and the Peltier Effect

“…The slow diffusion rate of a redox polymer may be overcome by using a flow-type thermocell, [6,45] and various types of redox flow batteries using redox-active polymers have been reported recently. [46][47][48][49] The maximum power density (P max ) of the PNV thermocell evaluated after a stabilization time of 120 s is an order of magnitude larger than that of the DPV thermocell, demonstrating the significance of attaching a redox molecule on a thermoresponsive polymer chain to improve the performance of thermocells (Figure 4f).…”

Analysis of Macromolecular Systems as Enabler for Energy and Life Science Applications

“…Arguably this would even mean moving away from the "polymer" concept of batteries. [172] Considering, the at least theoretically favorable properties of hyperbranched polymers as solvated and hydrated spheres (vide supra), the use of spherical nanoparticles with TEMPO-, viologen-, and diazaanthraquinonesubstituted polymer in an aqueous PRFB setting has been reported. [173] Due to electron propagation throughout the particle, overall charge transfer is enhanced.…”

Ferrocene to functionalized ferrocene: a versatile redox-active electrolyte for high-performance aqueous and non-aqueous organic redox flow batteries

“…The assembled cell maintained 2.4% of its initial capacity aer 100 cycles. 48 Another experiment was carried out by T. J. Sisto et al, aer preparing multiple ferrocene units in one derivative (36) (Fig. 14) that exhibited remarkable cycling stability for organic redox ow batteries.…”