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With the continuous increase of global plastics production, there is a demand to develop energy efficient processes to transform mixed plastic wastes into new products with enhanced utility - a concept that is often referred to as upcycling. Compatibilization is one of the most promising strategies to upcycle communal waste plastics. In this work, poly(ethylene terephthalate) (PET) and high-density polyethylene (HDPE), both widely used semicrystalline packaging polymers, are used as the target polymer blend. We systematically evaluate and compare three commercial ethylene copolymer based compatibilizers, ELVALOY™ AC 2016 Acrylate Copolymer (EAA), ELVALOY™ PTW Copolymer (PTW), and SURLYN™ 1802 Ionomer (Surlyn). They represent different compatibilization mechanisms. Furthermore, this work tackles a challenging question: where the compatibilizers are located in the blend. We discover that the location of the compatibilizer molecules can be predicted by comparing the crystallinity change of PET and HDPE in binary and ternary systems. Gaining this knowledge will facilitate root cause analysis of an ineffective compatibilizer and guide the design strategy to upcycle commingled waste plastics.

We report the dependence of mechanical properties and ionic conductivity of the Na1+xMnx/2Zr2–x/2(PO4)3 (designated as NMZP) ionic conductor on its composition (with x = 0.5, 1.0, 1.5, and 2.0). Lo...

Identifying and understanding charge storage mechanisms is important for advancing energy storage, especially when new materials and electrolytes are explored. Well-separated peaks in cyclic voltammograms (CVs) are considered key indicators of diffusion-controlled electrochemical processes with distinct Faradic charge transfer. Herein, we report on an electrochemical system with separated CV peaks, accompanied by surface-controlled partial charge transfer, in 2D Ti3C2Tx MXene in water-in-salt electrolytes. The process involves the insertion/desertion of desolvation-free cations, leading to an abrupt change of the interlayer spacing between MXene sheets. This unusual behavior increases charge storage at positive potentials, thereby increasing the amount of energy stored. This also demonstrates new opportunities for the development of high-rate aqueous energy storage devices and electrochemical actuators using safe and inexpensive aqueous electrolytes.

The correlation between solid electrolyte interphase (SEI) mechanical properties and battery electrochemical performances is complex and remains poorly understood. Gao et al. recently proposed a new mechanical parameter to predict the SEI stability, bringing new insights onto future battery design.

This work focuses on the mechanisms of interfacial processes at the surface of amorphous silicon thin-film electrodes in organic carbonate electrolytes to unveil the origins of the inherent nonpassivating behavior of silicon anodes in Li-ion batteries. Attenuated total reflection Fourier-transform infrared spectroscopy, X-ray absorption spectroscopy, and infrared near-field scanning optical microscopy were used to investigate the formation, evolution, and chemical composition of the surface layer formed on Si upon cycling. We found that the chemical composition and thickness of the solid/electrolyte interphase (SEI) layer continuously change during the charging/discharging cycles. This SEI layer "breathing" effect is directly related to the formation of lithium ethylene dicarbonate (LiEDC) and LiPF6 salt decomposition products during silicon lithiation and their subsequent disappearance upon delithiation. The detected appearance and disappearance of LiEDC and LiPF6 decomposition compounds in the SEI layer are directly linked with the observed interfacial instability and poor passivating behavior of the silicon anode.

Made available in DSpace on 2020-12-10T19:59:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-05-07 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center (EFRC) - DOE Office of Science, Office of Basic Energy Sciences NSERC The structure of electrical double layers at electrified interfaces is of utmost importance for electrochemical energy storage as well as printable, flexible, and bioelectronic devices, such as ion-gated transistors (IGTs). Here we report a study based on atomic force microscopy force-distance profiling on electrical double layers forming at the interface between the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and sol-gel films of mesoporous tungsten oxide. We successfully followed, under in operando conditions, the evolution of the arrangement of the ions at the interface with the tungsten oxide films used as channel materials in IGTs. Our work sheds light on the mechanism of operation of IGTs, thus offering the possibility of optimizing their performance. Univ Estadual Paulista, Dept Fis Quim, BR-14800060 Araraquara, SP, Brazil Polytech Montreal, Dept Genie Phys, Montreal, PQ H3C 3A7, Canada Oak Ridge Natl Lab, Ctr Nanophase Mat Sci, Oak Ridge, TN 37831 USA Univ Estadual Paulista, Dept Fis Quim, BR-14800060 Araraquara, SP, Brazil CAPES: FAPESP/CAPES 2014/27079-9 CAPES: 2015/50526-4 CAPES: 2016/09033-7

Summary Inorganic-organic hybrid solid electrolytes are promising material systems for all solid-state batteries (ASSBs). These electrolytes contain numerous solid | solid interfaces that govern transport pathways, electrode | electrolyte compatibility, and durability. This paper evaluates the role that electrode | electrolyte interfaces and electrolyte structure have on electrochemical performance. Atomic force microscopy techniques reveal how mechanical, adhesion, and morphological properties transform in a series of model hybrid solid electrolytes. These measurements are mapped to sub-surface microstructural features using synchrotron nano-tomography. Hybrid solid electrolytes with shorter polymer chains demonstrate a higher adhesion ( > 100 nN), Young's Modulus (6.4 GPa), capacity (114.6 mAh/g), and capacity retention (92.9%) than hybrid electrolytes with longer polymer chains (i.e., higher molecular weight). Extrinsic interfacial properties largely dictate electrochemical performance in ASSBs. Microstructural control over inorganic constituents may provide a means for tailoring interfacial properties in hybrid solid electrolytes.

Enhancing the energy stored and power delivered by layered materials relies strongly on improved understanding of the intricate interplay of electrolyte ions, solvents, and electrode interactions as well as the role of confinement. Here we report a highly integrated study with multiscale theory/modelling and experiments to track the intercalation of aqueous Li+, Na+, K+, Cs+, and Mg2+ ions into Ti3C2 MXene. The integrated analysis of experiments assisted by theory/modelling allows for a deep understanding of energy storage processes highlighting the importance of the dynamics of cations, their positionings between MXene sheets, their effects on mechanical properties and capacitive energy storage. Computational simulations and operando calorimetry measurements prove the processes involving cation dehydration and H+ rehydration, showing a good correlation for heat variations between experiments and theory. Operando liquid AFM mapped energy dissipation of ions appears non-uniformly across the MXene surface, indicating heterogeneities of ions inside the MXene and confirming partially the ion behaviour obtained in theory. We directly demonstrate that the average distance between the cation and MXene surface follows a modified two-sided Helmholtz model when plotted versus the open circuit potential capacitance, revealing a different electrical double layer mechanism in confinement. This new fundamental understanding lays the foundation for improved functional devices utilizing electrodes and membranes made of two-dimensional materials.

Reversible electrochemical intercalation of cations into the interlayer space of 2D materials induces tunable physical and chemical properties in them. In MXenes, a large class of recently developed 2D carbides and nitrides, low intercalation energy, high storage capacitance, and reversible intercalation of various cations have led to their improved performance in sensing and energy storage applications. Herein, a coupled nanopore-actuator system where an ultrathin free-standing MXene film serves as a nanopore support membrane and ionically active actuator is reported. In this system, the contactless MXene membrane in the electric field affects the cation movement in the field through their (de)intercalation between individual MXene flakes. This results in reversible swelling and contraction of the membrane monitored by ionic conductance through the nanopore. This unique nanopore coupled to a mechanical actuation system could provide new insights into designing single-molecule biosensing platforms at the nanoscale.

Advances in solid electrolytes (SEs) with superionic conductivity and stabilized electrode-electrolyte interfaces are key enablers for all-solid-state batteries (SSBs) to meet the energy density and cost targets for next-generation batteries for electric vehicles. Argyrodite sulfide-based electrolytes with the nominal composition Li6PS5X; where X= Cl and/or Br, I provide several key advantages over other types of SE counterparts, including (i) exceptionally high ionic conductivities up to 10-2 S/cm at room temperature (comparable to nonaqueous liquid electrolytes), (ii) availability of low temperature and inexpensive synthesis routes to produce glass, glass-ceramic, and crystalline structures, and (iii) soft mechanical properties facilitating material processing and solid-state battery (SSB) fabrication. Several key challenges exist for the practical use of the argyrodite sulfide-based electrolyte in an SSB: (i) scale-up synthesis to produce phase-pure materials, (ii) rationale processing method development to produce free-standing thin film SSEs, and (iii) identifying buried interfacial side-reaction products at the electrode/electrolyte interfaces using advanced characterization tools. In this talk, we will present our recent achievements focusing on tackling each of these challenges, including (i) solution-based synthesis of Li6PS5X; (ii) optimizing binder, slurry composition, and processing method to make Li6PS5X thin film (in-situ Raman spectroscopy and microscopy with complementary electrochemical impedance spectroscopy (EIS) to explore electrode/ Li6PS5X interfacial stability. Acknowledgment This research conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) is sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) in the Vehicle Technologies Office (VTO) through the Advanced Battery Materials Research (BMR) Program.

Among different electrochemical energy storage devices, the ones that store a higher amount of energy (e.g., batteries) often undergo larger ion insertion-induced structural transformation and volume change, which results in lower rate performance. The ones that store a lower amount of energy (e.g., supercapacitors) usually show gradual structural change and smaller volume change. There is a strong correlation between electrochemistry and mechanical properties. Understanding the electro-chemo-mechanical coupling and controlling the ion insertion-induced strain is crucial for achieving high power and high energy storage devices. In-situ atomic force microscopy (AFM) is well suited to tackle this task as it allows tracking local volume changes and other mechanical responses sub-nanometer spatial resolution under the conditions close to the device operation In this work, we monitored electrode volume change via in-situ AFM and demonstrated the electro-chemo-mechanical coupling behaviors during proton insertion into WO3 materials. The concept of mechanical cyclic voltammetry (mCV) curves was developed, and the relationship between electrochemical current and strain was investigated with simplified models. The results revealed multiple ion-intercalation processes with different mechanical responses are involved during electrode cycling. Local heterogeneity was investigated via mCV mapping, confirming that the charging mechanisms varied across the electrode. These local variations could be further correlated to local morphology, crystal orientations, or chemical compositions. We further demonstrate that the mCV approach is applicable to a variety of energy storage materials (e.g., birnessite and MXene) with the increasing complexity of current-deformation relationships. The work was supported by the Fluid Interface Reactions, Structures, and Transport (FIRST), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Measurements were performed at the Center for Nanophase Materials Sciences (CNMS), which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences.

Li metal anodes are the potential solution for high-energy batteries. One of the challenges of applying such a high-energy anode is Li dendrite growth, which results in short-circuit and thermal runaway. Current battery research focuses on developing solid electrolytes to serve as a physical barrier to prevent dendrite growth. However, the Li morphology change during plating and stripping, and the mechanisms of how Li dendrite grows and propagates into a complex composite solid electrolyte are poorly understood. Understanding and controlling Li morphology evolution, dendrite formation, and growth during cycling are crucial to developing dendrite suppression strategies for solid electrolytes and enabling high-energy lithium metal batteries. In this work, Li morphology evolution during initial cycling in a crosslinked PEO-based gel composite electrolyte full cell with NMC 811 cathode is monitored via post-mortem SEM. The results show that severe surface pitting occurs as early as the second stripping cycle. Pit formation and continuous dissolution is the main cause of Li surface roughening and dendrite growth mechanism in the model gel composite electrolyte. Comparing Li dendrite growth mechanisms in liquid, polymer, and solid electrolytes, the observed dendrite growth mechanism resembles that of the liquid electrolyte the most. This study suggests that strategies to improve the electrochemical reversibility of electrodeposited Li reported in liquid electrolytes to control Li morphology and prevent dendrite growth may be transferrable in a gel electrolyte. This work is sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory (ORNL), managed by UT-Battelle, LLC for the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. Part of the measurements was performed at the Center for Nanophase Materials Sciences (CNMS), which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences.

Integrating sulfide separators into solid-state batteries (SSBs) containing high energy cathodes typically requires one or more materials and engineering solutions including: (i) applying interfacial coatings to mitigate electrolyte decomposition, (ii) applying high stack pressures to form robust solid-solid contacts, and (iii) using alloying anodes to avoid Li dendrite formation. Despite the promise of these approaches, a lack of standardized testing protocols makes it difficult to directly compare results among different studies. To address this problem, the present work benchmarks the performance of SSBs containing β-Li3PS4 (LPS) separators and composite cathodes. By systematically varying the anode/cathode composition and stack pressure, this work demonstrates that cathode design is a major bottleneck for solid-state cells cycled at low rates (- 2). Operando stack pressure measurements show that, while mechanical confinement generally promotes higher active material utilization and cycling stability, this strategy alone does not address interfacial reactivity between LPS and high voltage cathodes. These results also demonstrate that stress evolution during cycling is dominated by volume changes at the Li metal anode. Finally, we show that FeS2 cathodes with moderate operating voltages (+) exhibit superior cycling performance compared to high voltage cathodes by facilitating formation of stable cathode/electrolyte interfaces.

Understanding the electrical double layer (EDL) structure at the solid/liquid interface is critical towards realizing the full potential of electrochemical applications using ionic liquids. In this work, the out-of-plane and in-plane EDL structures of PYR14-TFSI on graphite (HOPG) have been studied by in-situ electrochemical atomic force microscopy (AFM) and molecular dynamics (MD) simulation. AFM results revealed that the first adsorbed ion layer on HOPG consists of both disordered and ordered lateral domains. It has been found that the neighboring molecules in the x-y plane form intricate ordered lateral structures on length scale of hundreds of nanometers, and the out-of-plane EDL structure is independent of the in-plane structure. MD simulations under zero polarization showed that in the first adsorbed layer, cations have one preferred orientation while anions have two preferred orientations in relation to the HOPG surface, which might be the origin of the complex lateral ordering. When polarizing the surface, a hysteretic order-disorder transition of the lateral ordering in the first adsorbed layer can be observed by in-situ AFM, and the ordered domains disappear for high positive or negative voltages. Comparison with bias-dependent MD reveals that the existence of a bimodal anion distribution in the first absorbed layer can be linked to the observed transitions giving new insights into the origin of the structural domains, which can help understand unusual charge and discharge kinetics observed in similar systems.

Alkali ion insertion into Prussian blue from aqueous electrolytes is characterized with operando AFM and EQCM, showing coupling of current with deformation and mass change rates. Stable cycling occurs only with K+, attributed to its lower hydration energy. The (de)insertion of K+ results in reversible deformation even in the open framework structure.

Electrochemical energy storage is the key enabling component of electric vehicles and solar‐/wind‐based energy technologies. The enhancement of energy stored requires the detailed understanding of charge storage mechanisms and local electrochemical and electromechanical phenomena over a variety of length scales from atoms to full cells. Classical electrochemical techniques, such as voltammetry, represent the macroscopic electrochemical properties, and consequently do not allow to extract important information about local electrochemical reactions, ions adsorption, intercalations, and transport. Understanding, controlling, and tuning the local electrochemical functionalities in functional energy materials require in situ/operando techniques which limit the use of structural and functional characterization techniques that provide local information. Here, force‐based atomic force microscopies (AFMs) have provided novel insights into locally probing electrochemical mechanisms on tens of nanometer and even molecular length scales and provide a viable pathway to probe electrochemical processes in situ/operando. In this review, we highlight the contributions in the development and application of force‐based AFM methods to elucidate the local charge storage mechanism in a variety of energy‐related materials. We will focus in particular on methods or AFM modalities in a liquid electrolyte environment.

Nanostructured birnessite exhibits high specific capacitance and nearly ideal capacitive behaviour in aqueous electrolytes, rendering it an important electrode material for low-cost, high-power energy storage devices. The mechanism of electrochemical capacitance in birnessite has been described as both Faradaic (involving redox) and non-Faradaic (involving only electrostatic interactions). To clarify the capacitive mechanism, we characterized birnessite’s response to applied potential using ex situ X-ray diffraction, electrochemical quartz crystal microbalance, in situ Raman spectroscopy and operando atomic force microscope dilatometry to provide a holistic understanding of its structural, gravimetric and mechanical responses. These observations are supported by atomic-scale simulations using density functional theory for the cation-intercalated structure of birnessite, ReaxFF reactive force field-based molecular dynamics and ReaxFF-based grand canonical Monte Carlo simulations on the dynamics at the birnessite–water–electrolyte interface. We show that capacitive charge storage in birnessite is governed by interlayer cation intercalation. We conclude that the intercalation appears capacitive due to the presence of nanoconfined interlayer structural water, which mediates the interaction between the intercalated cation and the birnessite host and leads to minimal structural changes. Nanostructured birnessite exhibits high specific capacitance and, while an important electrode material for high-power energy storage devices, its capacitive mechanism remains unclear. Capacitive charge storage in birnessite is now shown to be governed by interlayer cation intercalation.

We study a conjectural formula for the maximal elements in the wavefront set associated with a theta representation of a covering group over $p$-adic fields. In particular, it is shown that the formula agrees with the existing work in the literature for various families of groups. We also recapitulate the results of an analogous formula in the archimedean case, which motivated the conjectural formula in the $p$-adic setting., 34 pages

Atomic and molecular resolved atomic force microscopy (AFM) images offer unique insights into materials properties such as local ordering, molecular orientation and topological defects, which can be used to pinpoint physical and chemical interactions occurring at the surface. Utilizing machine learning for extracting underlying physical parameters increases the throughput of AFM data processing and eliminates inconsistencies intrinsic to manual image analysis thus enabling the creation of reliable frameworks for qualitative and quantitative evaluation of experimental data. Here, we present a robust and scalable approach to the segmentation of AFM images based on flexible pre-selected classification criteria. Usage of supervised learning and feature extraction allows to retain the consideration of specific problem-dependent features (such as types of periodical structure observed in the images and the associated numerical parameters: spacing, orientation, etc.). We highlight the applicability of this approach for segmentation of molecular resolved AFM images based on crystal orientation of observed domains, automated selection of boundaries and collection of relevant statistics. Overall, we outline a general strategy for machine learning-enabled analysis of nanoscale systems exhibiting periodic order that could be applied to any analytical imaging technique.

Let G G be the real points of a simply connected, semisimple, simply laced complex Lie group, and let G ~ \widetilde {G} be the nonlinear double cover of G G . We discuss a set of small genuine irreducible representations of G ~ \widetilde {G} which can be characterized by the following properties: (a) the infinitesimal character is ρ / 2 \rho /2 ; (b) they have maximal τ \tau -invariant; (c) they have a particular associated variety O \mathcal {O} . When G G is split, we construct them explicitly. Furthermore, in many cases, there is a one-to-one correspondence between these small representations and the pairs (genuine central characters of G ~ \widetilde {G} , real forms of O \mathcal {O} ) via the map π ~ ↦ ( χ π ~ , A V ( π ~ ) ) \widetilde {\pi } \mapsto (\chi _{\widetilde {\pi }}, AV(\widetilde {\pi }) ) .

Here we investigate the competitive electrosorption of mono- and divalent phosphate anions through electrochemical desalination- and dilatometry-based experiments. Through in situ dilatometry, we monitor the strain at the electrode surface as anions and cations are electrosorbed. Strain measurements show that the presence of divalent ions promotes a greater than anticipated electrode expansion during cation (Na+) electrosorption. The expansion observed with Na+ equaled the expansion observed with HPO42–. Because the ionic radius of Na+ is smaller than that of HPO42–, the symmetric expansion suggests that divalent anions do not completely desorb during electrode regeneration, causing the adverse interactions with the cation during co-ion expulsion. This results in a decrease in desalination performance, indicated by a decreased salt adsorption capacity. Conversely, an expected asymmetric expansion during anion and cation electrosorption occurs with monovalent phosphate anions (H2PO4–), indicating that mono...

This paper provides a comparison between the K K -structure of unipotent representations and regular sections of bundles on nilpotent orbits for complex groups of type D D . Precisely, let G 0 = Spin ⁡ ( 2 n , C ) G_0 =\operatorname {Spin}(2n,\mathbb {C}) be the Spin complex group as a real group, and let K ≅ G 0 K\cong G_0 be the complexification of the maximal compact subgroup of G 0 G_0 . We compute K K -spectra of the regular functions on some small nilpotent orbits O \mathcal {O} transforming according to characters ψ \psi of C K ( O ) C_{ K}(\mathcal {O}) trivial on the connected component of the identity C K ( O ) 0 C_{ K}(\mathcal {O})^0 . We then match them with the K {K} -types of the genuine (i.e., representations which do not factor to SO ⁡ ( 2 n , C ) \operatorname {SO}(2n,\mathbb {C}) ) unipotent representations attached to O \mathcal {O} .

Recent years have witnessed the generation of a massive amount of spatialtextual data. In view of this, a new type of query coined spatial keyword query has been proposed to deal with the location-based services with additional keyword constraint. This paper studies one of the most popular spatial keyword queries called Top-k Spatial Keyword Query(TkSKQ). Explicitly speaking, given a set of objects, a TkSKQfinds the k objects that are closest to the querier with each of these k objects satisfying all the keywords specified by the query. This kind of query is of paramount importance in a variety of application domains such as location-based recommendation and advertisement.The state-of-art algorithm for processing a TkSKQis highly sensitive to the number of query keywords specified in the query such that its performance degrades significantly with an increase in the number of keywords. To remedy this drawback, this paper proposes a novel mechanism that utilizes an additional keyword list to enhance the efficiency of the existing solution. Based on this indexing technique, our algorithm needs only traverse a single quadtree when processing a TkSKQ. Moreover, we study how to prioritize the keywords in the vocabulary so as to optimize the performance of our technique. Furthermore, we deal with a generalized version of the TkSKQproblem, called HkSKQ. A similar technique can also be useful for solving HkSKQ. Experimental results on both synthetic and real data reveal the superiority of our proposed scheme.

Electrochemical reactions and ionic transport underpin the operation of a broad range of devices and applications, from energy storage and conversion to information technologies, as well as biochemical processes, artificial muscles, and soft actuators. Understanding the mechanisms governing function of these applications requires probing local electrochemical phenomena on the relevant time and length scales. Here, we discuss the challenges and opportunities for extending electrochemical characterization probes to the nanometer and ultimately atomic scales, including challenges in down-scaling classical methods, the emergence of novel probes enabled by nanotechnology and based on emergent physics and chemistry of nanoscale systems, and the integration of local data into macroscopic models. Scanning probe microscopy (SPM) methods based on strain detection, potential detection, and hysteretic current measurements are discussed. We further compare SPM to electron beam probes and discuss the applicability of electron beam methods to probe local electrochemical behavior on the mesoscopic and atomic levels. Similar to a SPM tip, the electron beam can be used both for observing behavior and as an active electrode to induce reactions. We briefly discuss new challenges and opportunities for conducting fundamental scientific studies, matter patterning, and atomic manipulation arising in this context.

A great effort has been centered around developing clean energy technologies (energy storage devices) to curtail burning fossil fuels’ deleterious environmental effects. Rechargeable batteries [lithium-ion batteries (LIBs)] are among the most invested and investigated storage devices showing potential to transform fossil fuel-powered mobility to next-generation safe electromobility. However, LIBs powered electric vehicles (EV) are expensive due to the high-cost graphite anode associated with LIBs. Herein, the synthesis of low-cost, highly crystalline nano-graphite with a tunable microstructural architecture has been demonstrated via molten salt assisted low-temperature electro-catalytic graphitization of coal chars, traditionally non-graphitizable carbon. Thus, graphite derived from coal chars exhibited nanoflake architecture and delivered high reversible capacity, stable long cycle life, and excellent electrochemical performance under fast charging/discharging conditions (5C, ∼12 min charge/discharge time). This finding paves the way to manufacture cost-effective high-energy-density batteries using as-synthesized graphite from readily available coal sources that could propel the EVs to the next level.

Understanding the mechanical response of an electrode during electrochemical cycling and its correlation to the device electrochemical performance is crucial to improving the performance of insertion-type energy storage devices, electrochemical actuators, water purification, ion separation and neuromorphic computing applications. In this work, we visualized the electro-chemo-mechanical coupling behaviors during charge storage of anhydrous and hydrated WO3 electrodes via in situ atomic force microscopy (AFM) and developed the concept of mechanical cyclic voltammetry (mCV) curves. The relationship between electrochemical current and strain was investigated with simplified models and the results revealed that the proton insertion/deinsertion process could be described through potential-dependent electro-chemo-mechanical coupling coefficients which might indicate changes in insertion processes during electrode cycling. The mCV mapping results highlight the local heterogeneity and show that the charging processes varied across the electrode. These local variations could be further correlated to local morphology, crystal orientations or chemical compositions with proper electrode designs.

Electrode deformations during charging and discharge process are directly related to the power performance and cyclability of the energy storage devices. Understanding the electrode deformation and changes in mechanical responses during electrochemical events and their impact on devices’ performance is crucial for achieving high power and high energy storage devices. In-situ atomic force microscopy (AFM) is well suited to tackle this task as it allows tracking local sub-nanometer volume changes and other mechanical responses. With a spatial resolution of tens of nanometer, this approach is capable of mapping the electro-chemo-mechanical behavior under the conditions close to the device operation and access information about local redox mechanisms. In this work, the electro-chemo-mechanical coupling behaviors of different pseudocapacitive materials was studied via in-situ AFM. The concept of mechanical cyclic voltammetry (mCV) curves was developed, and the relationship between electrochemical current and strain were investigated with simplified models. The results revealed that multiple ion-intercalation processes with different mechanical responses are involved during electrode cycling. The mechanical CV mapping highlighted the local heterogeneity and showed that the charging mechanisms varied across the electrode. These local variations could be further corelated to local morphology, crystal orientations or chemical compositions. Besides providing information of redox heterogeneity, the mechanical CV methodology allows us to circumvent the common issues that are often encountered in the global electrochemical characterizations, for example cell resistance and unwanted parasitic reaction. The work was supported by the Fluid Interface Reactions, Structures and Transport (FIRST), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Measurements were performed at the Center for Nanophase Materials Sciences (CNMS), which is sponsored at Oak Ridge National Laboratory by the Scientific User Facilities Division, Office of Basic Energy Sciences.

The presence of structural water leads to a transition of energy storage mechanism in tungsten oxide from battery-type intercalation (bulk diffusion limited) to pseudocapacitance (interface kinetics limited). In this study, we demonstrate that the energy storage mechanisms are linked to the material’s mechanical response to the intercalation process and present a method to study local electrochemical intercalation through mechanical coupling. We employed operando atomic force microscopy dilatometry (operando AFM dilatometry) to monitor the real-time mechanical response of WO3 and WO3·2H2O thin film electrodes during cyclic voltammetry in a 0.5 M H2SO4 electrolyte at sweep rates from 10 to 200 mV s-1 (80- to 4-second charge/discharge). This technique reveals that the deformation of WO3·2H2O is more facile and more gradual than that of WO3 during intercalation. We attribute the transition of energy storage mechanism to the more facile mechanical deformation of WO3·2H2O as compared to WO3. In addition, a mapping technique was developed to correlate local mechanical response from electrochemistry to the electrode nanostructure.

International audience; Two graphene-like carbide derived carbons (CDC-Gs) were produced by chlorination of SiC nanosheets obtained by magnesio-thermal reduction at moderate temperature of silica/graphene oxide nanocomposites. These CDC-Gs were evaluated as supercapacitor electrode materials in an organic electrolyte. Starting from a low SiO2/GO ratio in the precursor, the resulting CDC-G nanosheets are composed of a few layers of graphite, partially coated with microporous CDC. In contrast, a high SiO2/GO ratio leads to micropores generated on the basal plane of individual carbon nanosheets. The latter CDC-G shows a remarkable high power capability with 76 % of retention of the initial capacity at scan rates up to 3 V s−1. Notably, the equivalent series resistance (ESR) and time constant of the cell were found to be extremely low at 0.45 Ω·cm2 and 0.4 s, respectively, thanks to the unique 2D open surface and enhanced access to micropores. These features were attributed to the unique nanostructure of the microporous graphene.

This paper concerns the numerical solution of a fully nonlinear parabolic double obstacle problem arising from a finite portfolio selection with proportional transaction costs. We consider optimal allocation of wealth among multiple stocks and a bank account in order to maximize the finite horizon discounted utility of consumption. The problem is mainly governed by a time-dependent Hamilton–Jacobi–Bellman equation with gradient constraints. We propose a numerical method which is composed of Monte Carlo simulation to take advantage of the high-dimensional properties and finite difference method to approximate the gradients of the value function. Numerical results illustrate behaviors of the optimal trading strategies and also satisfy all qualitative properties proved in Dai et al. (2009) and Chen and Dai (2013).

A remarkable capacitance of 180F·g−1 (at 5mV·s−1) in solvent-free room-temperature ionic liquid electrolyte, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, was achieved in symmetric supercapacitors using microporous carbons with a specific surface area of ca. 2000m2·g−1 calculated from gas sorption by the 2D-NLDFT method. The efficient capacitive charge storage was ascribed to textural properties: unlike most activated carbons, high specific surface area was made accessible to the bulky ions of the ionic liquid electrolyte thanks to micropores (1–2nm) enabled by fine-tuning chemical activation. From the industrial perspective, a high volumetric capacitance of ca. 80F·cm−3 was reached in neat ionic liquid due to the absence of mesopores. The use of microporous carbons from biomass waste represents an important advantage for large-scale production of high energy density supercapacitors. Keywords: Supercapacitors, Activated carbon, Micropores, Ionic liquids

Research into the design of electrolytes of ionic liquids (ILs) for supercapacitor applications has grown in popularity in recent years. Unlike Li batteries where the composition of the electrolyte and the stability must meet several requirements (formation of SEI, electrochemical kinetics), the use of ionic liquids in supercapacitors opens interesting perspectives, in particular thanks to their high electrochemical stability. [1]. In this communication, it will be presented the results of an experimental study conducted using quartz crystal microbalance (eQCM) on nanoporous carbon based electrodes in contact with different electrolytes : neat IL and solvated IL as well as electrolyte mixture. EQCM turns out to be an effective analytic tool to bring new insights regarding the charge compensation mechanisms occurring while polarizing the carbon based electrode. In particular, it will be shown that charge compensation can involve different levels of desolvation of the counter-ions and that co-ions can also be used when the carbon electrode is polarized [2,3,4]. Références : [1] P. Simon et Y. Gogotsi, Nature Materials, 7 (2008) 845-854. [2] W.-Y. Tsai et al. JACS 8722−8728 (2014) [3] J. Griffin et al., Nature Materials, 22 juin 2015 (doi: 10.1038 / nmat4318). [4] Y.-C. Wu, P.-L. Taberna, P. Simon, Communications en électrochimie. 93, 119-122 (2018).

During natural evolution, the spindles often scale with cell sizes to orchestrate accurate chromosome segregation. Whether in cancer evolution, when the constraints on genome integrity are relaxed, cancer cells may evolve the spindle to confer other advantages has not been investigated. Using invasion as a selective pressure in vitro, we found that a highly metastatic cancer clone displays a lengthened metaphase spindle, with faster spindle elongation that correlates with transiently elevated speed of cell migration. We found that kinesin-5 is upregulated in this malignant clone, and weak inhibition of kinesin-5 activity could revert the spindle to a smaller aspect ratio, decrease the speed of spindle pole separation, and suppress post-mitotic cell migration. A correlation was found between high aspect ratio and strong metastatic potential in cancers that evolved and were selected in vivo, implicating that the spindle aspect ratio could serve as a promising cellular biomarker for metastatic cancer clones.

This paper presents a new approach to synthesizing self-aligned, uniform single-crystal cupric oxide (CuO) nanowires on a Cu-based multilayer on SiO 2 /Si. The key is to introduce CoWP as a nanofilter to catalyze CuO-nanowire synthesis simply by calcination at 400 °C in air. The CuO nanowires (diameter: 10–50 nm, length: 7 μm) exhibit low resistivity (10–60 Ω cm), a low turn-on field (4.5 V μm −1 ) and a high field-enhancement factor (∼1400).

Let R be a 2-torsionfree ring with identity 1 and let T n ( R ) , n ⩾ 2, be the ring of all upper triangular n × n matrices over R. We describe additive Jordan isomorphisms of T n ( R ) onto an arbitrary ring and generalize several results on this line.

International audience; Supercapacitors store charge through the electrosorption of ions on microporous electrodes. Despite major efforts to understand this phenomenon, a molecular-level picture of the electrical double layer in working devices is still lacking as few techniques can selectively observe the ionic species at the electrode/electrolyte interface. Here, we use in situ NMR to directly quantify the populations of anionic and cationic species within a working microporous carbon supercapacitor electrode. Our results showthat charge storage mechanisms are different for positively and negatively polarized electrodes for the electrolyte tetraethylphosphonium tetrafluoroborate in acetonitrile; for positive polarization charging proceeds by exchange of the cations for anions, whereas for negative polarization, cation adsorption dominates. In situ electrochemical quartz crystal microbalance measurements support the NMR results and indicate that adsorbed ions are only partially solvated. These results provide new molecular-level insight, with the methodology offering exciting possibilities for the study of pore/ion size, desolvation and other effects on charge storage in supercapacitors.

Phalaenopsis is the most important economic crop in the Orchidaceae family. There are currently numerous beautiful and colorful Phalaenopsis flowers, but only a few species of Phalaenopsis have an aroma. This study reports the analysis volatile components present in P. Nobby’s Pacific Sunset by solid-phase microextraction (SPME) coupled with gas chromatography (GC) and gas chromatography/mass spectrometry (GC-MS). The results show that the optimal extraction conditions were obtained by using a DVB/CAR/PDMS fiber. A total of 31 compounds were identified, with the major compounds being geraniol, linalool and α-farnesene. P. Nobby’s Pacific Sunset had the highest odor concentration from 09:00 to 13:00 on the eighth day of storage. It was also found that in P. Nobby’s Pacific Sunset orchids the dorsal sepals and petals had the highest odor concentrations, whereas the column had the lowest.