Search

This is the ShakeFlow: Functional Hardware Description with Latency-Insensitive Interface Combinators paper artifact submitted for evaluation of the 28th International Conference on Architectural Support for Programming Languages and Operating Systems (ASPLOS`23). This repository is also available as-is on github: https://github.com/kaist-cp/shakeflow

It is urgent to develop a new anode material that addresses the needs on high energy density as well as high power density of Li-ion batteries to meet the growing demands of high-performance mobile devices and electric vehicles. In this work, a new ternary composite (Si–Sn–C) anode material was designed to achieve exceptional rate performance by scavenging lost Si charge capacity at higher working potential of Sn (~ 0.9 V) under increased current densities. Si and Sn nanoparticles were separately compartmentalized in double-holed carbon nanofibers (Si–Sn–DHCNFs) to elucidate the working potential effect without a kinetic improvement by Sn. Si–Sn–DHCNFs showed high specific capacity (1000 mA h g−1 at 100 mA g−1) and exceptional rate performance (720 mA h g−1 at 10,000 mA g−1). Our work demonstrates that the design of new anode materials is a fruitful route to enhancing the power density of batteries.

Nano-structured silicon anodes are attractive alternatives to graphite in lithium-ion batteries; however, despite recent progress in nano-engineered composites, its use remains limited. One of the issues, particularly in silicon-dominated anodes, is the poor Coulombic efficiency of lithium–silicon processes. Previous studies have shown that repeating the amorphous–crystalline hysteretic lithium–silicon phase transformations can abruptly improve irreversibility and eventually minimize cumulative irreversible lithium consumption in exchange of certain parasitic capacity sacrifice. Here, we reveal mechanism behind the phenomenon that the single phase transformation spontaneously and pseudo-topologically transforms nano-structured silicon into quantum-scale frameworks without gravimetric loss. The way it forms is clearly distinct from ever explored formation mechanism of porous nano-structures such as (electro)chemical etching, Kirkendall voiding, and percolation theory. Further, we implanted the structural transformation feature into lithium-ion full cells, largely redesigning the conventional one, by modulating cathode/anode capacity loading balance and prelithiation dose in the anode to embed the unique feature in the cells. We show that the cell preferentially triggers the efficient irreversibility-depletion phenomenon upon cycling and consequently outperforms conventional silicon-based cells.

The growing demand of numerous industries for clean energy sources necessitates the development of high performance lithium-ion batteries. This in turn requires a deeper understanding of the corresponding electrode degradation phenomena. The formation of the solid electrolyte interphase, formed by chemical reactions of active materials with the electrolyte, is a major factor governing the cycling-induced degradation of lithium-ion battery anode materials. Therefore, the visualization of solid electrolyte interphase layers and the characterization of their chemical and electrical properties are tasks of high practical importance. Herein, we visualize the solid electrolyte interphase layers formed inside lithium-ion battery anodes comprising a mixture of Si-C composites and graphite particles as active materials by scanning spreading resistance microscopy. Quantitative and comparative scanning spreading resistance microscopy of pristine and 100-fold cycled anodes reveal that the latter sample features solid electrolyte interphase layers exhibiting a prominently higher electrical resistance than the active materials and demonstrate that thick solid electrolyte interphase layers start to form in the voids between active materials in the cycled anodes with the capacity decreased by ∼17%. This study confirms that scanning spreading resistance microscopy is useful for characterizing solid electrolyte interphase layers and active materials in various lithium-ion battery electrodes.

The choice of materials that constitute electrodes and the way they are interconnected, i.e., the microstructure, influences the performance of lithium-ion batteries. For batteries with high energy and power densities, the microstructure of the electrodes must be controlled during their manufacturing process. Moreover, understanding the microstructure helps in designing a high-performance, yet low-cost battery. In this study, we propose a systematic algorithm workflow for the images of the microstructure of anodes obtained from a focused ion beam scanning electron microscope (FIB-SEM). Here, we discuss the typical issues that arise in the raw FIB-SEM images and the corresponding preprocessing methods that resolve them. Next, we propose a Fourier transform-based filter that effectively reduces curtain artifacts. Also, we propose a simple, yet an effective, global-thresholding method to identify active materials and pores in the microstructure. Finally, we reconstruct the three-dimensional structures by concatenating the segmented images. The whole algorithm workflow used in this study is not fully automated and requires user interactions such as choosing the values of parameters and removing shine-through artifacts manually. However, it should be emphasized that the proposed global-thresholding method is deterministic and stable, which results in high segmentation performance for all sectioning images.

To employ Li-based batteries to their full potential in a wide range of energy-storage applications, their capacity and performance stability must be improved. Si is a viable anode material for Li-based batteries in electric vehicles due to its high theoretical capacity and good economic feasibility. However, it suffers from physical and chemical degradation, leading to unstable electrochemical performance and preventing its incorporation in new Li-based battery systems. Herein, we applied a poly(vinyl alcohol)-PO4 protective coating for Si-graphite anodes and confirmed an improvement in the electrochemical performance. The experimental results revealed that the polymer acts as a binder to alleviate the pulverization of the electrode. Furthermore, the oxide coating reduces the loss of Li2O, which has high ionic conductivity, during operation, resulting in the formation of a stable solid electrolyte interphase. Our findings suggest that a stable and ion-conducting anode/interphase can be developed by apply...

The efficiency of certain additives like tryptophan (TRP), adenosine monophosphate (AMP) and phenethylamine (PEA) on polyamide membrane (PA) surface for better salt rejection is studied through density functional theory. The interaction energies of monovalent (Na + , K + ) and divalent (Ca 2 + , Mg 2 + ) cations with pure PA and modified PA surfaces are calculated and a stronger binding of divalent cations over monovalent cations is noticed. The increasing order of binding of PA surfaces with metal-ions is PA_PEA + + 2 + 2 + . Both gas phase and solvent phase interaction energies follow the same trend of metal ion binding to the PA surface. The findings from the interaction studies are supported by conceptual density functional descriptors. TRP and AMP bound PA surfaces with polar functional groups are relatively presented as an effectual membrane surface for salt rejection than the pure polyamide surface.

Comb-like hydroxyl poly(oxyethylene) methacrylate homopolymer (HPOEM) and zwitterionic carboxylated polyethyeleneimine (carboxylated PEI) were synthesized and applied to the surface of commercially available seawater reverse osmosis (SWRO) membranes to introduce fouling resistance. The successful synthesis of the polymers and modification of the membrane surface were confirmed by X-ray photoelectron spectroscopy, zeta potential and contact angle measurements. Fouling test of the surface-modified membranes with alginate and bovine serum albumin showed opposite behavior at high salt concentrations: a salting-out effect on the HPOEM-coated membrane and a salting-in effect on the carboxylated PEI-coated membrane. HPOEM-coated SWRO membranes showed better fouling resistance under brackish conditions. However, the zwitterionic carboxylated PEI-coated membrane showed higher affinity to sodium chloride solution than deionized water, and presented an inhibitory effect to foulant adsorption under seawater conditions. This indicates that an effective fouling resistant layer specialized for seawater filtration could be prepared with zwitterionic materials.

Pumping regimes for water distribution systems have been established to reduce pump operation costs. Optimization of water reservoir networks has been studied extensively for operating pumps efficiently. According to research, optimization reduces pump operation costs by approximately 10–20%. However, comparing economic benefits per country would be too complex because the effects of optimization differ depending on the power cost estimation system of each country and the existing operations. This study presents an optimization algorithm to minimize the operating costs of an entire system via the application of dynamic programming. Case studies were conducted to apply the algorithm to real values in four scenarios. By setting cost minimization as an objective, an optimum water pump operation plan was derived that encompasses operating conditions, variations in water demand, and energy costs. Results showed that operating a standby pump in an existing system can increase the system's efficiency. In addition, even if hourly water consumption remains constant, each case requires its own operating method, because each case has different operational costs. By considering various conditions such as those mentioned in this study, future pump operation schedules can be optimized and stabilized to maintain economic water supply.

We have shown using both experiments and simulations that incorporation of polyoctahedral oligomeric silsequioxanes (POSS) into the active layer of polyamide (PA) thin film composite membrane results in higher water flux and salt rejection than pure PA membranes. We report that the water flux increased by a factor of 1.32 and salt rejection increased from 99.0% to 99.62% for the PA–POSS. Molecular dynamics simulation was employed to study the effect of POSS on membrane polymerization, water and salt diffusion and free volume. Quantities, such as water diffusivity, water partition coefficient, fractional free volume and range of free volume size computed on the equilibrated configurations, increased on the inclusion of POSS in PA membranes. Moreover salt diffusivity was lower in PA–POSS than PA. Therefore from the simulation study, it was concluded that the introduction of POSS into PA membrane improved (a) porosity of composite membrane, (b) hydrophilicity and (c) charge on the membrane. These effects explain the increase of water flux and salt rejection in nanocomposite membranes.

A novel multiscale porous architecture where an individual particle is nested inside a hollow chamber of inverse-opal (IO) frame is created using a large scale self-assembly of core-shell structured colloidal particles and subsequent selective removal of the outer shells of the colloids. Since the nested particle is smaller than the size of individual IO chamber, the interconnected nanochannels are spontaneously formed within the structured frame. The size of internal nanochannels is readily tuned to have high permeability and size-selective separation capability, which is successfully tested for nanoparticle separation.

The use of forward osmosis (FO) process for seawater desalination has attracted tremendous interest in recent years. Besides the manufacture of suitable membranes, the major technical challenge in the efficient deployment of the FO technology lies in the development of a suitable "draw solute". Owing to its inherent advantages, poly(aspartic acid) has arisen to be an attractive candidate for this purpose. However, an investigation of its molecular level properties has not been studied in detail. In this paper, the dynamics of poly(aspartic acid) and its sodium salt in the dilute concentration regime have been reported. The quantification of the polymer conformational properties, its solvation behavior, and the counterion dynamics are studied. The neutral polymer shows a preferentially coiled structure whereas the fully ionized polymer has an extended structure. Upon comparing with poly(acrylic acid) polymer, another polymer which has been used as a draw solute, poly(aspartic acid) forms more number of hydrogen bonds as well as fewer ion pairs.

A reduced order model (ROM) is derived for the Donnan Steric Pore Model (DSPM) [Bowen and Welfoot, Chem. Engng. Sci. 57 (2002) 1121], using volume averaging principles. DSPM has coupled ordinary differential equations and requires an iterative solution procedure. The proposed ROM reduces the original differential equations to set of algebraic equations. It has a direct solution, leading to elegant parameter extraction and spreadsheet implementation. When applied to desalination data at nominal salt concentrations, charge density and salt rejections predicted by ROM compare well with detailed DSPM results. The water flux across desalination membranes reduces as feed salinity increases. This experimental data can be used to back-calculate the concentration polarization mass transfer coefficient using the method developed by Sutzkover et al. Desalination 131 (2000) 117. Once concentration polarization effects are accounted for using their method, the proposed ROM describes the water flux and salt rejection data accurately for a wide range of feed concentrations without any additional parameters.

Acetylated cellulose ethers (ACEs), a new family of cellulosic polymers, were synthesized via the esterification of hydroxyl alkyl cellulose (HAC). The average molecular weight of the ACEs was in the range 220–280 kDa, much higher by an order of magnitude than that of cellulosic polymers commonly used for membrane materials, thereby giving rise to better physical and chemical properties than conventional cellulosic polymers. Dense ACE membranes were first prepared to study fundamental transport behaviors in terms of the permeability, the apparent diffusion coefficient and the solubility coefficients of water and salt (e.g., NaCl). The water permeability and salt passage in ACE membranes were comparable with other cellulosic polymers such as cellulose acetate (CA) and cellulose triacetate (CTA), based on the trade-off relation between water permeability and water/salt selectivity. Novel ACEs showed good solubility in common organic solvents such as dimethylformamide (DMF), dimethylacetamide (DMAC), and N-methyl-2-pyrrolidone (NMP), leading to easy membrane fabrications in various membrane structures, e.g., ACE thin-film composite (TFC) membranes (as a selective thin layer), and microporous asymmetric ACE membranes (as a microporous supporting layer). In this study, such various membrane structures were investigated by using novel cellulosic polymers, ACEs, and then they were evaluated for potential desalination applications such as reverse osmosis (RO) and forward osmosis (FO).

Amphiphilic organic/inorganic hybrid star-shaped polymers (SPP) were prepared by atom transfer radical polymerization (ATRP) using poly(ethylene glycol) methyl ether methacrylate (PEGMA) and 3-(3,5,7,9,11,13,15-heptacyclohexyl-pentacyclo[9.5.1.1³,⁹.1⁵,¹⁵.1⁷,¹³]-octasiloxane-1-yl)propyl methacrylate (MA-POSS) as monomers and octakis(2-bromo-2-methylpropionoxypropyldimethylsiloxy)-octasilsesquioxane (OBPS) as an initiator. Star-shaped polymers (SPM) having PEGMA and methyl methacrylate (MMA) moieties were also prepared for comparative purposes. Polysulfone (PSf) ultrafiltration membranes coated with the SPP showed higher bio- and oil-fouling resistance and flux-recovery ability than the bare PSf membrane. Moreover, the SPP-coated membranes exhibited better antifouling properties than the SPM-coated membrane when they were used for oil/water emulsion filtration. The dual effective antifouling properties of the SPP were ascribed to the simultaneous enrichment of hydrophilic PEG and hydrophobic POSS moieties on the membrane surfaces resulting in the decrease in interactions with proteins and the increase in repellence to oils.

A novel means of layer-by-layer deposition (LbL) of polyelectrolyte multilayers on three-dimensionally porous inverse opal (3D-IO) structures is presented. The 3D-IO structures comprising UV-curable polymer are highly flexible and can be readily demonstrated as free-standing films with double-sided open porosity over a large scale. A conflict between the intrinsically hydrophobic polymeric structures and waterborne characteristics of the LbL deposition process is overcome by employing a mixed solvent system of water and alcohol. The deposition pH of the LbL assembly can strongly affect the charge density and the degree of entanglement of polyelectrolyte chains, resulting in contrastingly different film deposition and growth behaviors. Since this method utilizes a three-dimensionally structured surface as a deposition substrate, 3D-IO films with a thickness of tens of micrometers can be uniformly and completely deposited with polyelectrolyte multilayers using only several tens of bilayer depositions, which can offer a new pathway of fabricating functionalized polymeric films. Finally, the LbL treated 3D-IO films are applied to nanofiltration membranes for removing multivalent metallic cations. Due to the enhanced Donnan exclusion effect as a result of multiple interfaces formed inside the 3D-IO structures and the relatively large volumetric ratio of water-permeable polyelectrolyte complexes, outstanding membrane performance was observed. Specifically, a good rejection rate of metal ions was achieved even under highly diluted feed conditions without sacrificing the high permeation flux.

Due to its simple process and low energy consumption, forward osmosis (FO) has gained significant attention in the fields of portable hydration bags, desalination, landfill leachate treatment, and brine concentration. However, current state-of-the-art reverse osmosis (RO) membranes show relatively low water fluxes in FO processes due to high internal concentration polarization (ICP) and high mass transfer resistance in commercially available microporous support membranes. In this study, carboxylated polysulfones (CPSFs) were synthesized via direct polysulfone (PSF) functionalization and considered as hydrophilic, mechanically stable microporous support membranes. The incorporation of hydrophilic groups into hydrophobic polymer backbones often reduces mechanical strength due to excessive water swelling. However, the mechanical properties of CPSFs (degree of substitution, DS=0.49–0.85) were similar to those of pristine PSF, and they retained their hydrophilic nature. Microporous CPSF membranes were prepared in various conditions, and FO water fluxes and salt passages of polyamide thin-film/CPSF composite membranes were measured and compared with each other. CPSF-based FO membranes showed significantly higher water fluxes (water flux in FO mode: 18 L/m 2 h, salt passage: 2.2 g/m 2 h under 1 M MgCl 2 as a draw solution, active layer facing DI water) than PSF-based FO membranes (10.5 L/m 2 h, 1.5 g/m 2 h at the same conditions), which might be due to enhanced hydrophilicity and reduced ICP.

Poly (aspartic acid sodium salt) (PAspNa) was evaluated for its potential as a novel draw solute in forward osmosis (FO). The inherent advantages of PAspNa, such as good water solubility, high osmotic pressure, and nontoxicity, were first examined through a series of physicochemical analyses and atomic-scale molecular dynamics simulations. Then, lab-scale FO tests were performed to evaluate its suitability in practical processes. Compared to other conventional inorganic solutes, PAspNa showed comparable water flux but significantly lower reverse solute flux, demonstrating its suitability as a draw solute. Moreover, fouling experiments using synthetic wastewater as a feed solution demonstrated that PAspNa reversely flowed to the feed side reduced inorganic scaling on the membrane active layer. The recyclability of PAspNa was studied using both nanofiltration (NF) and membrane distillation (MD) processes, and the results exhibited its ease of recovery. This research reported the feasibility and applicability of FO-NF or FO-MD processes using PAspNa for wastewater reclamation and brackish water desalination.

A nanocolander network is developed by embedding mesoporous block copolymers inside the structural frame of a macroporous inverse-opal structure. Spontaneously formed macroconduits interconnecting the macropores are utilized as internal bypasses for enhancing the bulk transport properties. A demonstrative application for the membrane of the nanocolander network is of perfect size-selectivity for nanoparticle separation without compromising the high permeability of the transporting medium.

DOI: 10.1002/adma.201305862 However, strong van der Waals interactions and subsequent irreversible aggregation of the nanomaterials makes it unlikely for the assembled system to exhibit unidirectional alignment. This limitation can be overcome by employing “intelligent” (i.e., responsive) and fl exible one-dimensionally structured biomaterials. [ 11,12 ] The self-assembled structures of M13 viruses are an example; their mechanical stiffness and structural characteristics are readily controlled by manipulating the environmental pH or the type of bonding with the underlying substrate. [ 13,14 ]

Silicon is an alternative anode material for future energy storage devices because it delivers 10 times greater theoretical (>3579 mAh/g) specific capacity than that of a traditional graphite anode (>370 mAh/g). However, Si-based anode materials face significant challenges due to its large volume expansion (~270-300%) upon lithium insertion. This large volume change causes cracking and pulverization of silicon, which leads to loss in electrical contact and drastic capacity fading. In addition, a continuous growth of solid electrolyte interphase (SEI) due to Si cracking causes low Coulombic efficiency, higher resistance to electronic/ionic transport. This will eventually deplete Li resevoir and limit the anode capacity. To address this challenge, various strategies have been explored through nanostructured material design such as nano/micro-sized Si powders, nano-Si composites, Si nanowires/nanotubes, core-shell type nano/micron Si anodes.1 Despite the significant advances in Si anodes, there still remains critical challenges to overcome, one of the most basic which is poor Coulombic efficiencies (CEs) that unfortunately often remain to be examined. Here we studied multiple factors that can lead higher CEs in both half and full cells. We link such electrochemical performance to Si structural transformations in long-term cycles, being probed via a variety of atomistic-level short/long range techniques, such as ex situ nuclear magnetic resonance (NMR),2 ex situ x-ray diffraction (XRD), 3 ex situ X-ray absorption fine structure (XAFS), and ex situ transmission electron microscopy (TEM). The detail will be presented at the conference. References 1. Obrovac, M. N. & Krause, L. J. Journal of the Electrochemical Society 154, A103-A108, (2007) 2. Ogata, K. et al. Nat Commun 5, 3217 (2014). 3. Li, J. & Dahn, J. R. Journal of the Electrochemical Society 154, A156-A161, doi:Doi 10.1149/1.2409862 (2007).

To response the dramatically increased demand in portable electronics, hybrid electric vehicles and large scale energy storage over the last decade, Li-ion batteries (LIBs) with higher energy density and power capability have been strongly desired. With respect to the anode if LIB, silicon have received a great deal of interest as fully lithiated (ca. Li22Si5) alloy has the highest theoretical capacity of any known material at 4140 mAh/g (3579 mAh/g for Li15Si4 at room temperature). Although it is about 10 times higher than that of conventional graphite anode, Si-based electrode has yet to find use in commercial application because of its low coulombic efficiency (C.E.) and poor capacity retention. Si is typically known to undergo over 300% of volume expansion on Li insertion, which leads to cracking and crumbling of active particles and the resultant loss of electrical contact between electro-active materials causes rapid capacity fading. Although extensive researches have been reported to alleviate the problems, most of approaches are commercially unviable as they usually involve complicated and prohibitively high cost processes. Hence, a Si anode with sufficient performances and low cost production is highly desired. At first, this study presents a novel cost-saving Si-base anode material with high coulombic efficiency and prolonged cyclability of excellent electrochemical performances using a low-cost synthesis of attractive route. As a part of our strategy, we attempted to employ a by-product derived from a granular poly-Si mass production system for the feedstock of solar cell application. In such a way, a certain amount of amorphous Si particles (ASP), the by-product, is derived homogeneously from the nucleation of gas dust in silane-based gas phase reactor. Our pioneering attempt is advantageously characterized by follows: 1) obtained sub-micron sized Si particle is superior to nano-sized Si in battery performances and business value and 2) the production cost is expected to be significantly lower than commercially available nano-Si by utilizing the by-product from an already matured mass production system. Further improvement in consideration of commercial feasibility and processing cost is achieved by employing ASP into spherical Si/graphite composite systems. In the optimized system, the mechanical stress of Si particles induced by huge volume expansion on Li insertion is further alleviated and the direct contact between Si and electrolyte is prevented, by which irreversible reaction leading to deterioration of coulombic efficiency is reduced. In this context, we have performed a systematic study on the influence of choice and application method of carbon materials which is a critical element in the composites. In such a way, the achieved advantageous characteristics are summarized as follows: 1) well-distributed Si particles in the composite system preventing agglomeration and 2) a strong bonding between Si and graphite maintaining electrical contact under repeated charge-discharge, 3) a ductile matrix to buffer the huge stress caused by the volume expansions and 4) buffer spaces inside the composite to accommodate the volume swings. It is worth noting that such an extraordinary ASP/graphite composite is manufactured in inexpensive way as the process is consists of only a few steps. The electrochemical characterization demonstrates remarkable performances as the coulombic efficiency at the first cycle reaches up to 91% and the capacity retention after 100 cycles is over 95% at 620 mAh/g. Material characterization is performed through several different analytical methods including HRTEM, in-situ solid state lithiation, in-situ dilatometer to elucidate and discuss the unique property of ASP and the superior performance of our spherical Si/graphite composite systems.

A series of star-shaped block (SBC) and random (SRC) copolymers containing poly(ethylene glycol) methyl ether methacrylate (PEGMA) and methyl methacrylate (MMA) moieties were prepared by atom transfer radical polymerization (ATRP), and used as membrane coating materials to investigate the effects of polymer structure and monomer content on the antifouling properties of the membranes. Polysulfone (PSf) ultrafiltration membranes coated with SBCs showed noticeably higher bio- and oil-fouling resistance than the bare PSf membrane. In addition, the SBC-coated membranes exhibited better antifouling properties than the SRC-coated membrane during both BSA solution and oil/water emulsion filtrations. The enhanced antifouling properties of the SBC-coated membrane compared to the SRC-coated one were ascribed to the larger content of denser PEG segments on the membrane surface, resulting in decreased interactions with proteins and oils.

Star-shaped polymers were prepared by atom transfer radical polymerization (ATRP) using poly(ethylene glycol) methyl ether methacrylate (PEGMA) and methyl methacrylate (MMA) as monomers and polyhedral oligomeric silsesquioxane (POSS) as a core material. Linear copolymers from PEGMA and MMA were also prepared for comparison purposes. Polysulfone (PSf) ultrafiltration membranes coated with the star-shaped polymer showed larger fouling resistance and flux recovery than those coated with the linear-shaped polymer. The improved antifouling properties of the star-shaped polymer compared with those of the linear polymer were ascribed to its larger oxygen to carbon ratio and smaller interactive forces with proteins.