ECS Meeting Abstracts

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EISSN : 2151-2043
Published by: The Electrochemical Society (10.1149)
Total articles ≅ 84,425
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, Lea Hong, Ponnambalam Ravi Selvaganapathy,
ECS Meeting Abstracts, pp 841-841;

The effect of electrochemical double layer (EDL) on the performance of graphene-based sensing platforms has been an area of controversy over the last two decades 1. The hydrophobic nature of bare graphene tends to repel the water and minimizes the solution/solid surface interactions 2. However, the presence of oxygen-based functional groups on graphene introduces negatively charged sites and causes a negative surface zeta potential. Hence, the instant formation of an EDL on a graphene surface in an aqueous solution is inevitable, affecting the graphene surface's chemical/physical interactions 3. Thus far, multiple theories and techniques have been developed to investigate the impact of EDL on graphene sensing performance; however, they either suffer from complexity in design or have ignored the co-existence of other solution parameters such as pH and oxidation-reduction potential 4.
Cara-Lena Nies, Michael Nolan
ECS Meeting Abstracts, pp 848-848;

Interfaces of 2D materials with metals are of interest for a large variety of applications, including sensors, batteries, catalysis, electronics, and semi-conductor devices. Transition metal dichalcogenides (TMDs) and specifically MoS2 are some of the most widely studied 2D materials. A detailed understanding of the interactions of metals with 2D TMDs can give useful insights into possible applications for metal-TMD systems. However, the literature focuses mainly on comparing trends in single atom adsorption and studying nanoparticles on MoS2monolayers.
Zimin She, Mariam Gad, Marianna Uceda,
ECS Meeting Abstracts, pp 855-855;

Silicon anodes are thought to soon replace graphite in next-generation Li-ion batteries due to silicon’s high capacity (3590 mAh/g for the Li15Si4 alloy at room temperature), availability and natural abundance. However, lithiation of silicon causes a large volume expansion (~300%) which can cause pulverization of the primary silicon particles, cracking and delamination of the bulk electrode and the formation of an unstable solid-electrolyte interface which must rebuild upon each cycle. Some combination of these effects leads to rapid anode failure via electrical isolation of active material and/or electrolyte depletion. To mitigate these challenges, clusters of silicon nanoparticles can be wrapped with flexible 2D-materials like graphene which can potentially act as a dimensionally and electrochemically stable, permeable barrier layers. This can be achieved in a scalable way via spray drying of aqueous dispersions of graphene oxide and silicon. In this talk, I will describe recent work from our group which aims to introduce a controlled amount of void space within the graphene protected silicon structures with the aim of engineering zero-strain silicon/carbon anode particles. In the absence of void space control, capillary forces acting during the spray drying process tightly wrap graphene around silicon clusters leaving little room for volume expansion. In one case, void space is introduced via incorporation of sacrificial polystyrene nanoparticles within the core by co-spray drying silicon, polystyrene and graphene oxide. In a second case, we do not use a sacrificial material but, instead, incorporate a responsive, cross-linked hydrogel within the core which can be expanded upon hydration to increase the volume of the graphene shell. When dehydrated, the gel shrinks to generate the required void space and acts as a Li-ion conducting, elastic binder within the core. In both cases, I will describe the systematic evolution of the crumpled graphene microstructure and its impact on anode performance in both half-cells and full Li-ion batteries.
Ayush Bhardwaj, Uzodinma Okoroanyanwu, James J. Watkins
ECS Meeting Abstracts, pp 859-859;

Graphene offers excellent electrical conductivity and very high surface area, which holds great promise for energy storage applications including supercapacitors. Current preparation methods for graphene require relatively long processing times, extremely high temperatures within controlled atmospheres, and/or involve multi-step reactions that present challenges for high throughput fabrication of graphene-based devices. We report a novel photothermal route to large-scale production of graphene within milliseconds using a commercially available benzoxazine polymer and a high intensity xenon flash lamp on various substrates including carbon fiber, Kapton and stainless steel at ambient conditions. The xenon flash lamp provides large-area illumination and a wide emission band (300 nm –1100 nm) that was used to convert the polymeric material directly into graphene upon millisecond exposures. The absorption spectrum of the precursor overlaps well with the maxima of the xenon flash lamp emission spectrum. The precursor material is heated to extremely high temperatures in a fraction of a second – a duration that is much shorter than the timescale for thermal equilibrium. This enables the conversion of the polymeric material to graphene in air and at room temperature, and without thermally damaging the substrate. Characterization of these graphene composites revealed high porosity, excellent conductivity, and good adhesion. Using carbon fiber as the substrate, we prepared micro-supercapacitors exhibiting a very high areal capacitance of 3.2 mF/cm2. Furthermore, we utilized the mechanically and chemically stable graphene/carbon fiber composite as a substrate for the electrochemical deposition of MnO2 which boosted the energy storage capability of the device. The obtained pseudocapacitor has an exceptional capacitance of 300 mF/cm2 at 1mA/cm2. The device retained more than 88% of its capacitance after charging/discharging for 2000 cycles. The preparation of high-quality graphene via photothermal pyrolysis of appropriate precursors is amenable to roll-to-roll processing, and thus large-scale production of electrochemical energy storage devices can be enabled by this approach.
Alexis Myers, Jeff Blackburn
ECS Meeting Abstracts, pp 865-865;

Efficient transfer of charge carriers and/or excitons between small organic molecules and two-dimensional (2D) semiconductor interfaces is being explored for applications in photovoltaics and quantum information processing.
Ann Rose Sebastian, Golam Kaium, Yeonwoong Jung, Ethan Ahn
ECS Meeting Abstracts, pp 867-867;

, , Mariana Desiree Reale Batista, Swetha Chandrasekaran, Bryan Moran, , Adam Carleton, , Daniel Tortorelli, Michael Stadermann, et al.
ECS Meeting Abstracts, pp 2460-2460;

Electrochemical energy storage (EES) and conversion devices (e.g. batteries, supercapacitors, and reactors) are emerging as primary methods for global efforts to shift energy dependence from limited fossil fuels towards sustainable and renewable resources. These electric-based devices, while showing great potential for meeting some key metrics set by conventional technologies, still face significant limitations. For example, an EES device tends to exhibit large energy density (e.g. lithium-ion battery) or power density (e.g. supercapacitor), but not both. This inability of a single device to simultaneously achieve both metrics represents a major obstacle to widespread adoption of EES devices. Improvements in materials, such as the integration of 2D materials (e.g. graphene, dichalcogenides, MXene, etc.) into electrochemical devices has yielded some exciting results towards tackling this issue, but significant improvements are still needed. Our approach to simultaneously achieving high energy and power density is to focus on one of the fundamental processes that occur in these systems: mass (or charge) transport. The efficient transport of ions within EES devices is critical to realizing both large power and energy densities. The pore structure of the electrode is a key factor in determining this transport phenomena, but in many cases, engineering the pore structure in a highly deterministic fashion is not pursued or even possible for many electrode materials. In this work, we explore a number of additive manufacturing methods (e.g. direct ink write, projection microstereolithography, etc.) to engineer the pore structure of device electrodes. We also determine effective electrode geometries using both simple theory and topology optimization techniques. The topology optimization couples the solution of the forward electrochemical problem over the full electrode domain with gradient-based optimization. The output of our code is a three-dimensional CAD representation which optimizes over specific performance metrics and which can be used to print functional electrodes. This work provides a systematic path toward automatic design and fabrication of engineered electrodes with precise control over the fluid and species distribution.
James W. Gittins, Alexander C. Forse
ECS Meeting Abstracts, pp 843-843;

Two-dimensional layered metal-organic frameworks (MOFs), characterised by their combined high intrinsic porosities and electrical conductivities, have emerged as one of the most promising electrode materials for next-generation energy storage devices, particularly supercapacitors. Several such MOFs have displayed encouraging performances in supercapacitors with a wide range of electrolytes, and have exhibited specific and areal capacitances on par with or exceeding state-of-the-art carbon materials.1-3 This has raised the prospect of using these materials in commercial devices, and their well-defined structures make them promising model electrode materials for supercapacitor structure-property investigations. However, layered MOFs can be synthesised with a range of particle morphologies, and hence 3D pore structures, as well as different degrees of particle agglomeration. Minimal work has been performed to understand how these factors impact the capacitive performances of these frameworks, and existing literature has struggled with small differences in observed morphology and low control over the samples.4 This has cast doubts over reported results, and has hindered both the development of MOF-based supercapacitors and their implementation as model electrodes.
Mark C Hersam
ECS Meeting Abstracts, pp 856-856;

Efficient energy storage systems represent a critical technology across many sectors including consumer electronics, electrified transportation, and a smart grid accommodating intermittent renewable energy sources. Arguably, the most important advance in energy storage over the past three decades is the lithium-ion battery, which was recently recognized with the Nobel Prize in Chemistry. However, despite its many successes, issues related to safety, energy density, charging time, and operating temperature range have hindered the realization of the full potential of lithium-ion battery technology, particularly in large-scale applications such as grid-level storage and full electrification of transportation networks. Nanostructured materials were once thought to present compelling opportunities for next-generation lithium-ion batteries, but inherent problems related to high surface area to volume ratios at the nanometer-scale (e.g., undesirable surface chemical interactions between electrodes and electrolytes) have impeded their adoption for commercial applications. This talk will explore how the chemical inertness of select two-dimensional (2D) materials are driving a resurgence in nanostructured lithium-ion battery materials [1]. For example, conformal graphene coatings on lithium-ion battery cathode powders mitigate surface degradation and minimize the formation of the solid electrolyte interphase, thus improving cycling stability [2]. In addition, the high electrical conductivity of graphene reduces cell impedance, resulting in enhanced kinetics that enable high-rate capability and low-temperature performance down to –20 °C [3]. On the other hand, ionogel electrolytes based on ionic liquids and hexagonal boron nitride (hBN) nanoplatelets provide safe, high-rate operation at high temperatures up to 175 °C, which represents the highest operating temperature to date for solid-state lithium-ion batteries [4,5]. The strong interfacial interactions between hBN and ionic liquids further enable novel electrolyte architectures based on layered heterostructure ionogels that result in unprecedently high energy densities and rate performance for solid-state batteries [6].
Andrea Ferrari
ECS Meeting Abstracts, pp 857-857;

Disruptive technologies are usually characterised by universal, versatile applications, which change many aspects of our life simultaneously, penetrating every corner of our existence. In order to become disruptive, a new technology needs to offer not incremental, but dramatic, orders of magnitude improvements. Moreover, the more universal the technology, the better chances it has for broad base success. Significant progress has been made in taking graphene and related materials from a state of raw potential to a point where they can revolutionize multiple industries. When it comes to electrochemical applications, Raman spectroscopy is an ideal non-destructive technique to study degradation in graphite anodes, as it is sensitive to doping, strain, defects, and interlayer coupling. I will discuss how in-situ Raman spectroscopy can unravel the signatures of Li-ion induced doping, intercalation staging and degradation upon cycling.
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