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Efficient charge transport pathways in solutions of redox-active polymers are essential for advancing nextgeneration energy storage systems. Herein, we report the grafting of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) and poly(2,2,6,6-tetramethyl-1-piperidinyloxy-4-yl methacrylate) (PTMA) polymer brushes onto silica particles with different molecular weights and grafting densities, and the impact of these composite particles in solutions of PTMA. The polymer-grafted particles are characterized using Fourier-transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR) spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and dynamic light scattering (DLS) techniques. The grafted polymers have molecular weights of 2.5 kDa and 5.0 kDa, with corresponding grafting densities of 0.688 and 0.378 chains nm−2 for SiO2-PTMA-2.5k and SiO2-PTMA-5k, respectively, with the grafting density decreasing with increasing graft length. To investigate the effect of these composite particles on charge transport in solutions of PTMA, different concentrations of the grafted particles were added to solutions of PTMA of different concentrations (near overlap concentration, C*) in 0.1 M LiTFSI in acetonitrile. Electrochemical analysis reveals that below C* the addition of SiO2-PTMA-5k increases the apparent diffusion coefficient (Dapp) 15.2% to 1.041 × 10−6 cm2 s−1 , the exchange rate constant (kex,app) by 9.5% to 1.546 × 1011 L mol−1 s−1, and the heterogeneous electron transfer rate constant (k0) by 24.6%, to 5.526 × 10−4 cm s−1. These results indicate that the synergistic interactions between unbound PTMA polymer chains in solution and PTMA-grafted particles facilitate interchain charge transfer kinetics. This highlights that grafted redoxactive particles can enhance charge transport without the limitations of polymer-only solutions (e.g., chain entanglement) and presents a promising design strategy for high-performance electrochemical applications, such as redox flow batteries (RFBs). 

Redox-active polymers serving as the active materials in solid-state electrodes offer a promising path toward realizing all-organic batteries. While both cathodic and anodic redox-active polymers are needed, the diversity of the available anodic materials is limited. Here, we predict solid-state structural, ionic, and electronic properties of anodic, phthalimide-containing polymers using a multiscale approach that combines atomistic molecular dynamics, electronic structure calculations, and machine learning surrogate models. Importantly, by combining information from each of these scales, we are able to bridge the gap between bottom-up molecular characteristics and macroscopic properties such as apparent diffusion coefficients of electron transport (Dapp). We investigate the impact of different polymer backbones and of two critical factors during battery operation: state of charge and polymer swelling. Our findings reveal that the state of charge significantly influences solid-state packing and the thermophysical properties of the polymers, which, in turn, affect ionic and electronic transport. A combination of molecular-level properties (such as the reorganization energy) and condensed-phase properties (such as effective electron hopping distances) determine the predicted ranking of electron transport capabilities of the polymers. We predict Dapp for the phthalimide-based polymers and for a reference nitroxide radical-based polymer, finding a 3 orders of magnitude increase in Dapp (≈10–6 cm2 s–1) with respect to the reference. This study underscores the promise of phthalimide-containing polymers as highly capable redox-active polymers for anodic materials in all-organic batteries, due to their exceptional predicted electron transport capabilities.