No abstract

Polymeric binders are essential to battery electrodes, mechanically stabilizing the active materials. Most often, these binders are insulating, and conductive carbons must be added to the electrode structure. Conductive polymer binders, those that transport both ions and electrons, are of primary interest because they potentially eliminate the need for carbon additives. However, it is challenging to incorporate both ion- and electron-conductive polymeric binders into electrode systems because of differences in physical affinities among the two polymer types and the electroactive material. Here, we investigate amphiphilic polymeric binders comprised of electron- and ion-conducting poly(3-hexylthiophene)-block-poly(ethylene oxide) (P3HT-b-PEO) as compared to P3HT, PEO, and a blend of P3HT/PEO homopolymers in carbon-free VO cathodes. The electrode with P3HT-b-PEO binder has the highest capacity of 190 mAh/g, whereas VO is only 77 mAh/g at a C rate of 0.1 after over 200 cycles: a 2.5-fold improvement. Similarly P3HT, PEO, and the blend have capacities of 139, 130, and 70 mAh/g, which are not nearly as impressive as the block copolymer binder. The unique architecture of P3HT-b-PEO, wherein P3HT and PEO blocks are covalently bonded, promotes the uniform distribution of conductive binders within the VO structure, whereas the analogous P3HT/PEO blend suffers from phase separation. This work demonstrates that conductive block copolymer binders enable carbon-free electrodes for lithium-ion battery systems.

Crystalline vanadium pentoxide (VO) has attracted significant interest as a potential cathode material for energy storage applications due to its high theoretical capacity. Unfortunately, the material suffers from low conductivity as well as slow lithium ion diffusion, both of which affect how fast the electrode can be charged/discharged and how many times it can be cycled. Colloidal crystal templating (CCT) provides a simple approach to create well-organized 3-D nanostructures of materials, resulting in a significant increase in surface area that can lead to marked improvements in electrochemical performance. Here, a single layer of open shell VO architectures ca. 1 μm in height with ca. 100 nm wall thickness was fabricated using CCT, and the electrochemical properties of these assemblies were evaluated. A decrease in polarization effects, resulting from the higher surface area mesostructured features, was found to produce significantly enhanced electrochemical performance. The discharge capacity of an unpatterned thin film of VO (∼8.1 μAh/cm) was found to increase to ∼10.2 μAh/cm when the material was patterned by CCT, affording enhanced charge storage capabilities as well as a decrease in the irreversible degradation during charge-discharge cycling. This work demonstrates the importance of creating mesoscale electrode surfaces for improving the performance of energy storage devices and provides fundamental understanding of the means to improve device performance.

As a result of the increasing emphasis on accessing unconventional deposits of heavy oil and bitumen to meet global energy needs, there is an intense focus on addressing the rheological challenges involved in the transportation, handling, and processing of viscous hydrocarbons. While the design of superhydrophobic surfaces has been extensively explored, the fabrication of surfaces nonwetted by low-surface-tension and high-viscosity oils that can be scaled to meet industrial needs remains to be adequately addressed. Here, we demonstrate that colloidally templated architectures of TiO2 particles applicable through a facile spray deposition process can form 3D inverse opal coatings adhered to low-alloy steels. Low-temperature sintering induces necking of particles, giving rise to an interconnected framework of plastrons surrounded by necked TiO2 ligaments. Surface functionalization with 1H,1H,2H,2H-perfluorooctanephosphonic acid yields a helical surface monolayer with pendant trifluoromethyl moieties. The combination of interconnected plastrons, re-entrant curvature, and low surface energy suspends liquid droplets, of both water and heavy oil, in the Cassie–Baxter regime, yielding contact angles of 164° ± 5° and 161° ± 2°, respectively. The interconnected network of plastrons further enables the facile gliding of heavy oil (<100 s) upon immersion within a bath, whereas a comparable untreated surface remains completely fouled. The performance of this coating suggests a promising solution to mitigate the challenges of handling viscous oils in midstream applications and furthermore delineates a route to designing coatings for a broad host of rheologically challenging fluids.

Development of catalyst-controlled C-H hydroxylation could provide direct access to valuable synthetic targets, such as primary metabolites. Here, we report a new family of porous materials, comprised of 2-dimensional metalloporphyrin layers and flexible aliphatic linkers, and demonstrate C-H hydroxylation activity. We demonstrate that the stereochemistry of cis-decalin oxidation provides a useful tool for differentiating catalysis in from catalysis on porous materials, which is critical to leveraging the potential of porous materials for catalyst-controlled oxidation chemistry.