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Cross-linking poly(glycidyl methacrylate) microparticles with redox-responsive bis(5-amino-l,3,4-thiadiazol-2-yl) disulfide moieties yield redox-active particles (RAPs) capable of electrochemical energy storage via a reversible 2-electron reduction of the disulfide bond. The resulting RAPs show improved electrochemical reversibility compared to a small-molecule disulfide analogue in solution, attributed to spatial confinement of the polymer-grafted disulfides in the particle. Galvanostatic cycling was used to investigate the impact of electrolyte selection on stability and specific capacity. A dimethyl sulfoxide/magnesium triflate electrolyte was ultimately selected for its favorable electrochemical reversibility and specific capacity. Additionally, the specific capacity showed a strong dependence on particle size where smaller particles yielded higher specific capacity. Overall, these experiments offer a promising direction in designing synthetically facile and electrochemically stable materials for organosulfur-based multielectron energy storage coupled with beyond Li ion systems such as Mg.

Block copolymer electrolytes (BCE) such as polystyrene-block-poly(ethylene oxide) (SEO) blended with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and composed of mechanically robust insulating and rubbery conducting nanodomains are promising solid-state electrolytes for Li batteries. Here, we compare ionic solvation, association, distribution, and conductivity in SEO-LiTFSI BCEs and their homopolymer PEO-LiTFSI analogs toward a fundamental understanding of the maximum in conductivity and transport mechanisms as a function of salt concentration. Ionic conductivity measurements reveal that SEO-LiTFSI and PEO-LiTFSI exhibit similar behaviors up to a Li/EO ratio of 1/12, where roughly half of the available solvation sites in the system are filled, and conductivity is maximized. As the Li/EO ratios increase to 1/5 the conductivity, of the PEO-LiTFSI drops nearly 3-fold, while the conductivity of SEO-LiTFSI remains constant. FTIR spectroscopy reveals that additional Li cations in the homopolymer electrolyte are complexed by additional EO units when the Li/EO ratio exceeds 1/12, while in the BCE, the proportion of complexed and uncomplexed EO units remains constant; Raman spectroscopy data at the same concentrations show that Li cations in the SEO-LiTFSI samples tend to coordinate more to their counteranions. Atomistic-scale molecular dynamics simulations corroborate these results and further show that associated ions tend to segregate to the SEO-LiTFSI domain interfaces. The opportunity for "excess" salt to be sequestered at BCE interfaces results in the retention of an optimum ratio of uncompleted and complexed PEO solvation sites in the middle of the conductive nanodomains of the BCE and maximized conductivity over a broad range of salt concentrations.

With the ability to modulate electronic properties through molecular doping coupled with ease in processability, semiconducting polymers are at the forefront in enabling organic thermoelectric devi...

Cross-linked polymer electrolytes containing structurally dynamic disulfide bonds have been synthesized to investigate their combined ion transport and adhesive properties. Dynamic network polymers of varying cross-link densities are synthesized via thiol oxidation of a bisthiol monomer, 2,2'-(ethylenedioxy)diethanethiol, and tetrathiol cross-linker, pentaerythritol tetrakis(3-mercaptopropionate). At optimal loading of lithium bis(trifluoromethane-sulfonyl-imide) (LiTFSI) salt, the ionic conductivities (σ) at 90 °C are about 1 × 10

This work represents a joint computational and experimental study on a series of n-ethylene glycol (PEOn)-terminated quaterthiophene (4T) oligomers for 1 < n < 10 to elucidate their self-assembly b...

Conducting organic materials, such as doped organic polymers

Poly(ethylene oxide) (PEO) was the first lithium‐ion conducting polymer developed 50 years ago and is still the most popular electrolyte matrix for solid‐state lithium metal batteries. While many studies focus on increasing PEO ionic conductivity through doping with Li salts, little work has addressed using PEO and Li directly to generate Li+‐conducting species in situ. Reaction between PEO and Li leads to ionic conductivity largely from Li+, in contrast to the case of added salts where the anion contribution dominates. Herein, electrochemical impedance spectroscopy shows the ionic conductivity of PEO thin films increases up to three orders of magnitude (from 10−7 to 10−4 S cm−1) when contacted with Li at elevated temperature. This is due to the reduction of ether bonds, which produces lithium alkoxides that are responsible for Li+ transport. Density functional theory analysis confirms this mechanism as thermodynamically favorable. X‐ray photoelectron spectroscopy also shows the presence of organolithium species and Li2O, which are responsible for propagating reactions with PEO and forming an electronically insulating layer at the PEO–Li interface that halts further reaction, respectively. The underlying mechanisms of Li–polymer electrolyte reactions is clarified and new pathways for in situ Li+ doping of polymer electrolytes is presented.

Developing soft materials with both ion and electron transport functionalities is of broad interest for energy-storage and bioelectronics applications. Rational design of these materials requires a fundamental understanding of interactions between ion and electron conducting blocks along with the correlation between the microstructure and the conduction characteristics. Here, we investigate the structure and mixed ionic/electronic conduction in thin films of a liquid crystal (LC) 4T/PEO4, which consists of an electronically conducting quarterthiophene (4T) block terminated at both ends by ionically conducting oligoethylenoxide (PEO4) blocks. Using a combined experimental and simulation approach, 4T/PEO4 is shown to self-assemble into smectic, ordered, or disordered phases upon blending the materials with the ionic dopant bis(trifluoromethane)sulfonimide lithium (LiTFSI) under different LiTFSI concentrations. Interestingly, at intermediate LiTFSI concentration, ordered 4T/PEO4 exhibits an electronic conductivity as high as 3.1 × 10-3 S/cm upon being infiltrated with vapor of the 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) molecular dopant while still maintaining its ionic conducting functionality. This electronic conductivity is superior by an order of magnitude to the previously reported electronic conductivity of vapor co-deposited 4T/F4TCNQ blends. Our findings demonstrate that structure and electronic transport in mixed conduction materials could be modulated by the presence of the ion transporting component and will have important implications for other more complex mixed ionic/electronic conductors.

Although extensive efforts have been devoted to understanding electronic transport in conjugated polymers, little is known about their ionic conduction characteristics in relation to polymer chemistry, processing, and morphology. This work presents a combined computational and experimental study on morphology and ion transport in thin-film blends of polythiophene derivatives bearing oligoethylene glycol side-chains and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Using molecular dynamics (MD) simulation, we show that in the amorphous phase, the polythiophene derivative P3MEET bearing oligoethylene glycol side-chains with oxygen directly attached to the thiophene rings possesses lower Li+ ionic conductivity compared to its analog P3MEEMT that has a methyl spacer between the oxygen and the thiophene rings. Structural characterization of P3MEET and P3MEEMT thin film upon blending with LiTFSI indicates that adding LiTFSI expands the side-chain domains of the polymer crystallites and reduces the total ...

Role of Water Molecules in Enabling Site Hopping and Vehicular Transport Mechanisms in Polynorbornene-based Anion Exchange Membrane Zhongyang Wang, ⸹ Ge Sun ， ⸹ Mrinmay Mandal, ‡, Paul A. Kohl, ‡, Juan de Pablo, ⸹ Shrayesh N. Patel, ⸹ and Paul F. Nealey ⸹ ‡ School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, 30332-0100, United States ⸹ Pritzker School of Molecular Engineering, University of Chicago, Chicago, Illinois 60637, USA Ion exchange membranes are at the heart of electrochemical conversion and storage devices such as fuel cells 1, water electrolyzers 2, CO2 electrolyzers 3. redox flow batteries 4, and reverse electrodialysis 5. Anion exchange membrane fuel cells (AEMFCs) have attracted enormous attention as alternatives to replace perfluorinated, sulfonic acid-based proton exchange membrane fuel cells (PEMFCs) 6 because alkaline membrane electrode assemblies (MEAs) composed of anion exchange ionomers (AEIs) and AEMs that allow the use of Ni 7, 8, Fe 9, and Ag 10 based precious-group-metal (PGM) free catalysts in alkaline environments for hydrogen oxidation reactions (HORs) and oxygen reduction reactions (ORRs). However, the lack of understanding of ion transport mechanisms at different hydration levels of an anion exchange membrane hinders the rational design of the MEAs in an AEMFC. Here we investigate site hopping and vehicular transport mechanisms using anion exchange thin films, interdigitated electrodes, and atomistic molecular dynamics simulations. Halide ion (Br-, Cl- and I-) conductivities in polynorbornene-based thin films are measured as a function of temperature and relative humidity using electrochemical impedance spectroscopy. Halide ions show Arrhenius behaviors, and activation energy (Ea) is for the first time used as an indicator for detecting the transition of site hopping and vehicular transport mechanisms. Using atomistic molecular dynamics simulation, we quantitatively demonstrate that the transition of site hopping and vehicular mechanisms is aided by better solvation environments of anions and more percolated water pathways. References Z. Wang, J. Parrondo, C. He, S. Sankarasubramanian and V. Ramani, Nature Energy, 2019, 4, 281-289. S. Z. Oener, M. J. Foster and S. W. Boettcher, Science, 2020, 369, 1099-1103. D. A. Salvatore, C. M. Gabardo, A. Reyes, C. P. O’Brien, S. Holdcroft, P. Pintauro, B. Bahar, M. Hickner, C. Bae, D. Sinton, E. H. Sargent and C. P. Berlinguette, Nature Energy, 2021, 6, 339-348. K. Lin, Q. Chen, M. R. Gerhardt, L. Tong, S. B. Kim, L. Eisenach, A. W. Valle, D. Hardee, R. G. Gordon, M. J. Aziz and M. P. Marshak, Science, 2015, 349, 1529-1532. R. D. Cusick, Y. Kim and B. E. Logan, Science, 2012, 335, 1474-1477. J. Wang, Y. Zhao, B. P. Setzler, S. Rojas-Carbonell, C. Ben Yehuda, A. Amel, M. Page, L. Wang, K. Hu, L. Shi, S. Gottesfeld, B. Xu and Y. Yan, Nature Energy, 2019, 4, 392-398. G. Braesch, Z. Wang, S. Sankarasubramanian, A. G. Oshchepkov, A. Bonnefont, E. R. Savinova, V. Ramani and M. Chatenet, Journal of Materials Chemistry A, 2020, 8, 20543-20552. S. Kabir, K. Lemire, K. Artyushkova, A. Roy, M. Odgaard, D. Schlueter, A. Oshchepkov, A. Bonnefont, E. Savinova, D. C. Sabarirajan, P. Mandal, E. J. Crumlin, Iryna V. Zenyuk, P. Atanassov and A. Serov, Journal of Materials Chemistry A, 2017, 5, 24433-24443. H. Adabi, A. Shakouri, N. Ul Hassan, J. R. Varcoe, B. Zulevi, A. Serov, J. R. Regalbuto and W. E. Mustain, Nature Energy, 2021, 6, 834-843. H. Erikson, A. Sarapuu and K. Tammeveski, ChemElectroChem, 2019, 6, 73-86.

Mechanically robust, thermoresponsive, ion-conducting nanocomposite films are prepared from poly(2-phenylethyl methacrylate)-grafted cellulose nanocrystals (MxG-CNC-g-PPMA). One-component nanocomposite films of the polymer-grafted nanoparticle (PGN) MxG-CNC-g-PPMA are imbibed with 30 wt % imidazolium-based ionic liquid to produce flexible ion-conducting films. These films with 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (MxG-CNC-g-PPMA/[H]) not only display remarkable improvements in toughness (>25 times) and tensile strength (>70 times) relative to the corresponding films consisting of the ionic liquid imbibed in the two-component CNC/PPMA nanocomposite but also show higher ionic conductivity than the corresponding neat PPMA with the same weight percent of ionic liquid. Notably, the one-component film containing 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (MxG-CNC-g-PPMA/[E]) exhibits temperature-responsive ionic conduction. The ionic conductivity decreases at around 60 °C as a consequence of the lower critical solution temperature phase transition of the grafted polymer in the ionic liquid, which leads to phase separation. Moreover, holding the MxG-CNC-g-PPMA/[E] film at room temperature for 24 h returns the film to its original homogenous state. These materials exhibit properties relevant to thermal cutoff safety devices (e.g., thermal fuse) where a reduction in conductivity above a critical temperature is needed.

Knowledge of intrinsic properties is of central importance for materials design and assessing suitability for specific applications. Self-assembling block copolymer electrolytes (BCEs) are of great interest for applications in solid-state energy storage devices. A fundamental understanding of ion transport properties, however, is hindered by the difficulty in deconvoluting extrinsic factors, such as defects, from intrinsic factors, such as the presence of interfaces between the domains. Here, we quantify the intrinsic ion transport properties of a model BCE system consisting of poly(styrene

The interfacial region where ion-transporting polymer chains are anchored to a hard, insulating phase is a major factor dictating the limits of ion-conduction in nanostructure-forming electrolytes. In this work, we investigate the effect of an end-grafted poly(ethylene oxide) (20 kg mol−1) surface on the ionic conductivity σ of PEO and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt mixtures. Specifically, we characterize nanothin films in the range of ca. 10 to 250 nm, which amplify the contributions from the polymer/substrate interface that dictate any deviations from expected bulk conductivity σbulk values. Conductivity measurements reveal a monotonic decrease in σ upon decreasing film thickness at all values of r (r = molar ratio of Li+ to EO units). The reduction from bulk-like σ occurs for film thicknesses approximately 100 nm and below for all values of r. This trend in conductivity arises from the presence of the underlying grafted-PEO layer. Through a thickness dependence normalized conductivity study, we observe nanoscale constraints leading to deviation from intrinsic conductivity of bulk PEO–LiTFSI electrolytes. These nanoscale constraints correspond to an immobile interfacial zone whose thickness hint ranges from 9.5 ± 1.4 nm at r = 0.01 to 2.9 ± 1.5 nm at r = 0.15 in our nanothin films that impedes ion transport. Overall, we have presented a robust platform that facilitates probing the role of polymer-grafted surfaces on the σ of polymer electrolytes.

The electronic structure and molecular orientation of semiconducting polymers in thin films determine their ability to transport charge. Methods based on near-edge X-ray absorption fine structure (NEXAFS) spectroscopy can be used to probe both the electronic structure and microstructure of semiconducting polymers in both crystalline and amorphous films. However, it can be challenging to interpret NEXAFS spectra on the basis of experimental data alone, and accurate, predictive calculations are needed to complement experiments. Here, we show that first-principles density functional theory (DFT) can be used to model NEXAFS spectra of semiconducting polymers and to identify the nature of transitions in complicated NEXAFS spectra. Core-level X-ray absorption spectra of a set of semiconducting polymers were calculated using the excited electron and core-hole (XCH) approach based on constrained-occupancy DFT. A comparison of calculations on model oligomers and periodic structures with experimental data revealed ...

The tendency of metals to form uncontrolled dendritic morphologies during electrodeposition hinders the development of safe and reliable metal batteries. Multiphase nanostructured electrolytes can suppress dendritic growth if the mechanical modulus of the electrolyte is high relative to that of the metal or if the conducting channels are confined to nanoscale dimensions. Direct visualization and analysis of electrodeposition within polymeric nanostructures elucidates the structure−property relationships and mechanisms underlying the suppression of dendrite growth. To overcome these challenges, we introduce here a generalizable platform by which we can directly characterize electrodeposited metal morphologies in well-defined, multiphase nanostructured electrolytes by top-down SEM imaging [1]. This approach requires no destructive sample preparation techniques between electrodeposition and imaging. The platform consists of coplanar electrodes coated by polymeric structures consisting of alternating ion conducting and nonconducting material which are precisely created by lithography and etch techniques. These fabricated polymeric structures are designed to carefully model deposition of metals in nanostructured polymeric separators and electrolytes. In this study we track the electrodeposition of silver ions (Ag+) dissolved in dry, aprotic poly(ethylene oxide) (PEO) polymer electrolyte confined within channels that are defined by a microfabricated nonconductive polystyrene structures. We find that Ag metal electrodeposition occurs only in the conductive domains with no significant deformation of the adjacent low-modulus nonconductive and confining domains. Moreover, we have shown that the Ag metal deposit morphology was strongly dependent on the dimensions of the conducting domains. When confinement width was similar in scale to the critical length scale for unstable deposition, the metal morphology was dense, unbranched filaments. Gradually increasing the confinement width led to branched dendritic deposition, although the side branch feature size was limited by the size of the confinement. These results demonstrate that in addition to mechanical and transport properties, the nanodimension of the structured electrolyte can also serve to stabilize dendritic morphology growth. This work highlights critical parameters for design of structured battery components such as solid-electrolytes, separators, and current collectors. [1] Sharon, D.; Bennington, P.; Patel, S.N.; Nealey, P.F.*, “Stabilizing Metal Electrodeposition by Limiting Spatial Dimensions in Nanostructured Electrolytes,” ACS Energy Lett. 2020, 5, 2889−2896. Figure 1

Author(s): Bonnassieux, Y; Brabec, CJ; Cao, Y; Carmichael, TB; Chabinyc, ML; Cheng, KT; Cho, G; Chung, A; Cobb, CL; Distler, A; Egelhaaf, HJ; Grau, G; Guo, X; Haghiashtiani, G; Huang, TC; Hussain, MM; Iniguez, B; Lee, TM; Li, L; Ma, Y; Ma, D; McAlpine, MC; Ng, TN; Osterbacka, R; Patel, SN; Peng, J; Peng, H; Rivnay, J; Shao, L; Steingart, D; Street, RA; Subramanian, V; Torsi, L; Wu, Y | Abstract: This roadmap includes the perspectives and visions of leading researchers in the key areas of flexible and printable electronics. The covered topics are broadly organized by the device technologies (sections 1–9), fabrication techniques (sections 10–12), and design and modeling approaches (sections 13 and 14) essential to the future development of new applications leveraging flexible electronics (FE). The interdisciplinary nature of this field involves everything from fundamental scientific discoveries to engineering challenges; from design and synthesis of new materials via novel device design to modelling and digital manufacturing of integrated systems. As such, this roadmap aims to serve as a resource on the current status and future challenges in the areas covered by the roadmap and to highlight the breadth and wide-ranging opportunities made available by FE technologies.

We demonstrate how processing methods affect the thermoelectric properties of thin films of a high mobility semiconducting polymer, PBTTT. Two doping methods were compared: vapor deposition of (tridecafluoro-1,1,2,2-tetrahydrooctyl)trichlorosilane (FTS) or immersion in a solvent containing 4-ethylbenzenesulfonic acid (EBSA). Thermally annealed, thin films doped by FTS deposited from vapor yield a high Seebeck coefficient (α) at high electronic conductivity (σ) and, in turn, a large power factor (PF = α2σ) of ∼100 μW m–1 K–2. The FTS-doped films yield α values that are a factor of 2 higher than the EBSA-doped films at comparable high value of σ. A detailed analysis of X-ray scattering experiments indicates that perturbations in the local structure from either dopant are not significant enough to account for the difference in α. Therefore, we postulate that an increase in α arises from the entropic vibrational component of α or changes in scattering of carriers in disordered regions in the film.

Ion-conducting membranes play a central role in electrochemical devices. The rise in anion exchange membrane fuel cell (AEMFC) research is attributed to the viability of using platinum-group-metal free electrocatalysts for hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR).1 However, there are two major obstacles to apply anion exchange membranes (AEMs) as separators in alkaline electrochemical energy conversion devices. The first challenge is to develop the AEM with hydroxide ion conductivities above 100 mS/cm at 70 °C. The second challenge is to synthesize stable AEM (especially stable cationic head-groups) that exhibit high durability in strongly alkaline environments (e.g. in the presence of nucleophilic OH- ions). To solve the first problem, a triblock copolymer-based polymer backbone has been developed to synthesize AEMs with high ion conductivities by engineering a phase-separated morphology. To address the second problem, cycloaliphatic quaternary ammonium based AEM have been prepared that demonstrate excellent alkaline stability. Except for the performance of the separator, there are other factors including the design of electrocatalysts for HOR and ORR, and the structure of catalyst layer contributes to overall fuel cell performance. Herein, significant amount of effort has been made to better design the ionomer/electrocatalysts interface and to better understand the transport of the ionomer in confined regime. The use of a pH-gradient-enabled microscale bipolar interface (PMBI) to effectively separate the anolyte and catholyte of a direct borohydride/ hydrogen peroxide liquid fuel cell (DBFC) has been engineered and demonstrated, which enables record high DBFC performance. 2 The PMBI-type electrodes provide a new and fascinating design to engineer fuel-cell membrane electrode assemblies. Interdigitated electrode arrays (IDEs) have been developed as a platform for highly sensitive electrochemical measurements of polymer thin film with thickness of less than 100 nm.3 The IDEs coupled with electrochemical impedance spectroscopy (EIS) has been demonstrated as an effective platform to probe ion transport of polymer thin film, which provide direct translation to the design of the ionomer in fuel cell. References (1) Arges, C. G.; Zhang, L. Anion Exchange Membranes’ Evolution toward High Hydroxide Ion Conductivity and Alkaline Resiliency. ACS Applied Energy Materials 2018, 1 (7), 2991-3012, DOI: 10.1021/acsaem.8b00387. (2) Wang, Z.; Parrondo, J.; He, C.; Sankarasubramanian, S.; Ramani, V. Efficient pH-gradient-enabled microscale bipolar interfaces in direct borohydride fuel cells. Nature Energy 2019, DOI: 10.1038/s41560-019-0330-5. (3) Sharon, D.; Bennington, P.; Liu, C.; Kambe, Y.; Dong, B. X.; Burnett, V. F.; Dolejsi, M.; Grocke, G.; Patel, S. N.; Nealey, P. F. Interrogation of Electrochemical Properties of Polymer Electrolyte Thin Films with Interdigitated Electrodes. J Electrochem Soc 2018, 165 (16), H1028-H1039, DOI: 10.1149/2.0291816jes.

Polymer electrolytes have demonstrated promise as solid electrolyte materials to enable lithium-metal batteries. However, majority of studies have focused only on thick samples (100’s of microns). It is important to note interfaces play a critical role on the performance of batteries, thus investigating polymer electrolytes in the context of nanothin films (5-100 nm) will lead to better understanding on how surfaces and interfaces influences charge transport properties. Here, we report on ion transport characteristics of nanothin films of PEO and LiTFSI blends as a function of salt concentration, temperature and film thickness. Ion transport measurements were successfully performed using impedance spectroscopy on films fabricated on custom-designed nanofabricated interdigitated electrode (IDE) devices. Importantly, thickness dependence study of ion transport shows a monotonic decrease in ionic conductivity upon decreasing film thickness from 250 nm to ca. 10 nm, and the effect is stronger at low salt concentrations. The decrease of ionic conductivity at thinner films originate from the increasing fraction of the immobilized layer near the polymer/substrate interface. In addition, these measurements reveal previously inaccessible diffusional processes that are critical to fully characterizing transport properties. We also extend our work towards nanostructured block copolymer nanothin film electrolytes (polystyrene-b-polyethylene oxide with LiTFSI). By carefully tuning the substrate surface energy, we can judiciously control block copolymer self-assembly and orientation to reveal previously inaccessible interfacial contributions that dictate the limits of ion-transport. Overall, our work shows that nanothin films in concert with IDEs is a powerful and versatile platform for studying a wide variety of confinement and surface functionalization effects on ion transport in a controlled and precise manner.

Scientific Named Entity Referent Extraction is often more complicated than traditional Named Entity Recognition (NER). For example, in polymer science, chemical structure may be encoded in a variety of nonstandard naming conventions, and authors may refer to polymers with conventional names, commonly used names, labels (in lieu of longer names), synonyms, and acronyms. As a result, accurate scientific NER methods are often based on task-specific rules, which are difficult to develop and maintain, and are not easily generalized to other tasks and fields. Machine learning models require substantial expert-annotated data for training. Here we propose polyNER: a semi-automated system for efficient identification of scientific entities in text. PolyNER applies word embedding models to generate entity-rich corpora for productive expert labeling, and then uses the resulting labeled data to bootstrap a context-based word vector classifier. Evaluation on materials science publications shows that the polyNER approach enables improved precision or recall relative to a state-of-the-art chemical entity extraction system at a dramatically lower cost: it required just two hours of expert time, rather than extensive and expensive rule engineering, to achieve that result. This result highlights the potential for human-computer partnership for constructing domain-specific scientific NER systems.

Solid polymer electrolytes for lithium batteries promise improvements in safety and energy density if their conductivity can be increased. Nanostructured block copolymer electrolytes specifically have the potential to provide both good ionic conductivity and good mechanical properties. This study shows that the previously neglected nanoscale composition of the polymer electrolyte close to the electrode surface has an important effect on impedance measurements, despite its negligible extent compared to the bulk electrolyte. Using standard stainless steel blocking electrodes, the impedance of lithium salt-doped poly(isoprene-b-styrene-b-ethylene oxide) (ISO) exhibited a marked decrease upon thermal processing of the electrolyte. In contrast, covering the electrode surface with a low molecular weight poly(ethylene oxide) (PEO) brush resulted in higher and more reproducible conductivity values, which were insensitive to the thermal history of the device. A qualitative model of this effect is based on the hypothesis that ISO surface reconstruction at the different electrode surfaces leads to a change in the electrostatic double layer, affecting electrochemical impedance spectroscopy measurements. As a main result, PEO-brush modification of electrode surfaces is beneficial for the robust electrolyte performance of PEO-containing block-copolymers and may be crucial for their accurate characterization and use in Li-ion batteries.

The orientational correlation length of domains in a semiconducting polymer controls its thermoelectric performance., The electrical performance of doped semiconducting polymers is strongly governed by processing methods and underlying thin-film microstructure. We report on the influence of different doping methods (solution versus vapor) on the thermoelectric power factor (PF) of PBTTT molecularly p-doped with FnTCNQ (n = 2 or 4). The vapor-doped films have more than two orders of magnitude higher electronic conductivity (σ) relative to solution-doped films. On the basis of resonant soft x-ray scattering, vapor-doped samples are shown to have a large orientational correlation length (OCL) (that is, length scale of aligned backbones) that correlates to a high apparent charge carrier mobility (μ). The Seebeck coefficient (α) is largely independent of OCL. This reveals that, unlike σ, leveraging strategies to improve μ have a smaller impact on α. Our best-performing sample with the largest OCL, vapor-doped PBTTT:F4TCNQ thin film, has a σ of 670 S/cm and an α of 42 μV/K, which translates to a large PF of 120 μW m−1 K−2. In addition, despite the unfavorable offset for charge transfer, doping by F2TCNQ also leads to a large PF of 70 μW m−1 K−2, which reveals the potential utility of weak molecular dopants. Overall, our work introduces important general processing guidelines for the continued development of doped semiconducting polymers for thermoelectrics.

Author(s): Patel, SN; Balsara, NP | Abstract: Guest editors Shrayesh N. Patel and Nitash P. Balsara introduce this themed collection on charge transporting nanostructured polymers for electrochemical systems.

A new class of high-performance n-type organic thermoelectric materials, self-doping perylene diimide derivatives with modified side chains, is reported. These materials achieve the highest n-type thermoelectric performance of solution-processed organic materials reported to date, with power factors as high as 1.4 μW/mK(2). These results demonstrate that molecular design is a promising strategy for enhancing organic thermoelectric performance.

In this article, we present a review of the thermoelectric properties of semiconducting polymers. Organic semiconductors have emerged as promising materials for the capture of low-grade waste heat and for local temperature control. The thermoelectric performance of a material is dictated by its electrical conductivity, thermopower, and thermal conductivity. The role of processing methods, particularly of alignment methods, on the electrical properties of polymers are described in the context of their thermoelectric properties. We review recent work on understanding the anisotropy of the thermal conductivity of polymers and present an outlook for future research directions toward improved organic thermoelectrics. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44403

Tertiary amines covalently tethered to electron-deficient aromatic molecules by alkyl spacers enable solid-state n-doping., A scarcity of stable n-type doping strategies compatible with facile processing has been a major impediment to the advancement of organic electronic devices. Localizing dopants near the cores of conductive molecules can lead to improved efficacy of doping. We and others recently showed the effectiveness of tethering dopants covalently to an electron-deficient aromatic molecule using trimethylammonium functionalization with hydroxide counterions linked to a perylene diimide core by alkyl spacers. In this work, we demonstrate that, contrary to previous hypotheses, the main driver responsible for the highly effective doping observed in thin films is the formation of tethered tertiary amine moieties during thin film processing. Furthermore, we demonstrate that tethered tertiary amine groups are powerful and general n-doping motifs for the successful generation of free electron carriers in the solid-state, not only when coupled to the perylene diimide molecular core, but also when linked with other small molecule systems including naphthalene diimide, diketopyrrolopyrrole, and fullerene derivatives. Our findings help expand a promising molecular design strategy for future enhancements of n-type organic electronic materials.

With the ability to tune ion transport and mechanical properties, polymer electrolytes have demonstrated promise as solid electrolyte materials for lithium-metal anode batteries. In particular, polyethylene oxide (PEO) and lithium salt mixtures have been the most widely studied polymer electrolyte system.1 Moreover, block copolymer electrolytes (e.g. block polystyrene-block-PEO) have yielded more advanced nanostructured architectures with increased mechanical robustness and efficient ion transport.2 Driven by their potential applications, enormous efforts have been devoted to elucidating mechanisms for ion transport and the formation of lithium dendrites. However, majority of reported studies have focused only on thick bulk samples (100’s of microns thick films). This is significant to note as interfaces3 play a critical role in the performance of batteries, but researchers have mostly inferred interfacial effects using bulk properties. As a consequence, we focus on investigating polymer electrolytes in the (ultra)-thin film regime (5-500 nm), which can be used as a platform to directly study fundamental interfacial effects. In addition, structural characteristics limiting charge transport in polymer electrolytes such as domain orientation and interconnectivity can be more easily probed using thin films.4 Ultimately, investigating polymer electrolyte in the context of thin films will lead to better fundamental understanding of charge transport in polymer electrolytes and the charge transfer limitations at the electrode/electrolyte interfaces. Here, we report on our initial study on charge transport and morphology of a model polymer electrolyte system (mixtures of PEO and LiTFSI, lithium bis(trifluoromethanesulfonyl)imide)) in the thin film regime (r = 0.15, where r is the molar ratio of lithium ions to ethylene oxide repeat units. This trend is consistent with the established theories that adding Li salt disrupts the crystallite structure of PEO and reduces the overall degree of crystallinity. Ionic transport measurements were performed using a.c. impedance spectroscopy on PEO-LiTFSI thin films on custom-designed interdigitated electrode devices (IDE). Above the melting point of PEO (≈ º60 C), the temperature dependence of ionic conductivity of all samples can be well-described using Vogel-Tammann-Fulcher (VTF) model. This suggests that segmental motion of PEO chains facilitate ionic transport in PEO-LiTFSI thin films. Ionic conductivity is found to increase with increasing salt concentration at first but decreases at high salt concentration. This is likely due to the reduced dissociation rate and increased glass transition temperature at high concentration, similar to the behavior of bulk samples.1,2 Our results have demonstrated the first successful fabrication and characterization of ionic transport in PEO-Li salt thin films. This provides an important step toward exploiting thin film configuration to reveal many morphological and interfacial effects on ion conduction mechanism of polymer electrolytes and will be subject of investigations in our future studies. REFERENCES S. Lascaud et al., Macromolecules, 27, 7469–7477 (1994). D. T. Hallinan and N. P. Balsara, Annu. Rev. Mater. Res., 43, 503–525 (2013) http://www.annualreviews.org/doi/abs/10.1146/annurev-matsci-071312-121705. E. Peled and S. Menkin, J. Electrochem. Soc., 164, A1703–A1719 (2017). Y. Kambe, C. G. Arges, S. N. Patel, M. P. Stoykovich, and P. F. Nealey, ECS Interface (2017).

Microphase separating block copolymers (BCPs) are attractive candidates as electrolytes and ion exchange membranes due to their ability to simultaneously optimize for two or more orthogonal material properties. For an example, BCP electrolytes have been synthesized with one mechanically stable domain and one ion conducting domain to overcome the inverse relationship of the two properties. These films can exhibit both high structural stability and high ionic conductivity at the bulk scale.1,2 However, the formation of nanoscale architectures results in the creation of domain interfaces, grain boundaries, and tortuous ion conduction pathways. In such a film, ions can experience transport pathways that are non-parallel to the applied electric field. To date, this structure transport relationship has been investigated in thick films with bicontinuous structures as well as thick films with nanoscale domains aligned across macroscopic scales.3–5 However, assumptions are made about structure when correlating to the transport. This is due to the difficulties of characterizing all possible nanoscale pathways across macroscales (e.g. 20 nm domains across a 1 cm2 x 1mm membrane).6 In this work, the structure - ion transport relationship was investigated by characterizing all possible ion transport pathways from one electrode to the other by assembling thin film morphologies on top of interdigitated electrodes. The poly(styrene)-block-poly(2vinyl pyridine) (PSbP2VP) model BCP thin film (ca. 40nm) was assembled into a variety of morphologies on top of interdigitated electrodes. Trench topographies were formed on top of the IDEs to confine the BCPs. Neutrality conditions of the trench walls and the substrate were controlled by grafting monohydroxy terminated brushes at different stages of device fabrication. The confined BCP was microphase separated using solvent vapor annealing. Following orientation, the P2VP domain was converted into n-methyl 2-pyrilidinium iodide converting the domain into an anion conductor.7 Due to the perpendicular orientation of the PS and P2VP domains to the substrate and free surface, simple top down metrology could be used to characterize all possible ion conduction pathways from one electrode to the other. Visual analysis software was used to quantify the pathways that were connected from one electrode to the other. Molecular dynamics simulations of the lamellae cross section were used to understand water and ion distributions near the PS/P2VP interface. The ion transport behavior was studied under different humidity, temperature, and degrees of functionalization conditions. With path information alone, the conductivity values of different morphologies could be predicted within experimental error. When the ion conduction pathways were aligned parallel to the applied electric field, the resulting conductivity approached 74% of the theoretical maximum conductivity predicted using the Sax Ottino model.8 The remaining 26% difference in the conductivity could be rectified by the reduced water content at the interface of the hydrophilic P2VP/NMP+ I- domain and the hydrophobic PS domain. With the knowledge of the structure and the dimensions of the interface, the ion conductivity of the parallel oriented film could be predicted within experimental error. Surprisingly, the conductivity of the isotropic fingerprint lamellae morphology could also be predicted within error by assuming: 1) that the resistance of the total conduction path is linearly related to the tortuosity of the conduction path and 2) that only the domains that are connected from one electrode to the other contribute to conductivity. As demonstrated, the control of morphology and the ability to quantify structure and ion transport is envisioned as an attractive analytical platform to understand the role of heterogenous interfaces of microphase separating systems on ion transport behavior. References Inceoglu, S. et al. ACS Macro Lett. 3, 510–514 (2014). Schulze, M. W., McIntosh, L. D., Hillmyer, M. A. & Lodge, T. P. Nano Lett. 14, 122–126 (2014). Majewski, P. W., Gopinadhan, M., Jang, W.-S. S., Lutkenhaus, J. L. & Osuji, C. O. J. Am. Chem. Soc. 40, 17516–17522 (2010). Chopade, S. A. et al. ACS Appl. Mater. Interfaces 9, 14561–14565 (2017). Chintapalli, M., Higa, K., Chen, X. C., Srinivasan, V. & Balsara, N. P. Polym. Phys. 55, 266–274 (2017). Kambe, Y., Arges, C. G., Patel, S. N., Stoykovich, M. P. & Nealey, P. F. ECS Interface (2017). Arges, C. G., Kambe, Y., Suh, H. S., Ocola, L. E. & Nealey, P. F. Chem. Mater. 28, 1377–1389 (2015). Sax, J. & Ottino, J. M. Polym. Eng. Sci. 23, 165–176 (1983).

© 2015 American Chemical Society. Conjugated semiconducting polymers, such as poly(3-hexylthiophene) (P3HT), are poised to play an integral role in the development of organic electronic devices; however, their performance is governed by factors that are intrinsically coupled: dopant concentration, carrier mobility, crystal structure, and mesoscale morphology. We utilize synchrotron X-ray scattering and electrochemical impedance spectroscopy to probe the crystal structure and electronic properties of P3HT in situ during electrochemical doping. We show that doping strains the crystalline domains, coincident with an exponential increase in hole mobility. We believe these observations provide guidance for the development of improved theoretical models for charge transport in semiconducting polymers.

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