[ { "id": "authors:g2ann-jcq17", "collection": "authors", "collection_id": "g2ann-jcq17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160422-085739345", "type": "conference_item", "title": "Chemically specific dynamic bond percolation model for computational screening of polymer electrolytes", "author": [ { "family_name": "Webb", "given_name": "Michael", "orcid": "0000-0002-7420-4474", "clpid": "Webb-M-A" }, { "family_name": "Savoie", "given_name": "Brett", "orcid": "0000-0002-7039-4039", "clpid": "Savoie-B-M" }, { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" }, { "family_name": "Miller", "given_name": "Thomas F., III", "orcid": "0000-0002-1882-5380", "clpid": "Miller-T-F-III" } ], "abstract": "Polymer electrolytes have significant promise for many lithium-ion battery applications because they are non-flammable,\nelectrochem. stable, and easily manufd. However, significant improvements in the ionic cond. of even state- of-the-art polymer\nelectrolytes is needed for technol. viability. The computationally- guided design of more conductive polymer electrolytes\nwould save significant time and monetary resources, but these efforts require both a better understanding of ion- transport\nmechanisms in polymers and the development of tools for screening candidate polymers prior to synthesis and\ncharacterization. Using atomistic mol. dynamics (MD) simulations, we provide new insights into the mechanisms of lithium-ion\ndiffusion in polymer electrolyte materials, including that the spatial distribution of lithium- ion solvation sites, in addn. to\npolymer segmental motion, is a crucial factor for detg. polymer electrolyte performance. In addn., we have leveraged these\ninsights to develop a powerful new coarse-grained simulation protocol that enables the rapid screening of large nos. of\npolymer electrolyte materials using short-timescale MD trajectories. In particular, we extend the well-known dynamic bond\npercolation model [J. Phys. 1983, 79, 3133- 3142] to utilize short MD trajectories to predict the distribution of ion solvation\nsites and the rate of hopping among the ion solvation sites. Among the most striking results from our initial studies is the\nunexpectedly good lithium-ion diffusivity of poly(trimethylene oxide-alt-ethylene oxide) by comparison to PEO, which is widely\nused. Efforts to screen upwards of 500 candidate polymer structures utilizing the new model are currently underway.", "publisher": "Caltech Library", "publication_date": "2016-03" }, { "id": "authors:q6khr-kq446", "collection": "authors", "collection_id": "q6khr-kq446", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160331-090441966", "type": "conference_item", "title": "Systematic computational and experimental investigation of lithium-ion transport mechanisms in polymer electrolytes", "author": [ { "family_name": "Webb", "given_name": "Michael A.", "orcid": "0000-0002-7420-4474", "clpid": "Webb-M-A" }, { "family_name": "Savoie", "given_name": "Brett M.", "orcid": "0000-0002-7039-4039", "clpid": "Savoie-B-M" }, { "family_name": "Balsara", "given_name": "Nitash P.", "orcid": "0000-0002-0106-5565", "clpid": "Balsara-N-P" }, { "family_name": "Coates", "given_name": "Geoffrey W.", "orcid": "0000-0002-3400-2552", "clpid": "Coates-G-W" }, { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" }, { "family_name": "Miller", "given_name": "Thomas F.", "orcid": "0000-0002-1882-5380", "clpid": "Miller-T-F-III" } ], "abstract": "Solid polymer electrolytes have been the subject of considerable fundamental and applied chem. research due to their\npotential application in battery technologies. Although polymer electrolytes based on poly(ethylene oxide) have been\nextensively characterized both exptl. and theor., little is known about ion transport in other polymer classes. In this talk, we\nwill describe an interdisciplinary collaboration that combines chem. synthesis, electrochem. characterization, and mol. dynamics\nand coarse- grained simulation to systematically investigate lithium- ion transport in a range of new polymer electrolytes.\nThe resulting anal. reveals a no. of surprising and transferable chem. insights, including that the obsd. lithium- ion diffusion\nmechanisms are governed principally by the connectivity of solvation sites rather than by polymer segmental mobility. The\nmechanistic insights obtained in this effort have significance for the screening, synthesis, and characterization of nextgeneration\npolymer electrolytes.", "publisher": "Caltech Library", "publication_date": "2016-03" }, { "id": "authors:62wax-te267", "collection": "authors", "collection_id": "62wax-te267", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150902-104745372", "type": "conference_item", "title": "Shear localization in associating polymer gels", "author": [ { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" }, { "family_name": "Omar", "given_name": "Ahmad", "orcid": "0000-0003-1871-9235", "clpid": "Omar-A" } ], "abstract": "Despite the ubiquity of phys. crosslinked polymer gels in natural and synthetic systems, a fundamental\nunderstanding connecting the dynamics and microstructure to the bulk rheol. behavior under large deformations\nremains a challenging and open problem. To explore this connection, we perform startup shear computer\nsimulations on phys. assocg. polymer gels and track the temporal and spatial dynamical and structural\nresponse. For deformation rates exceeding the characteristic relaxation time of the gel, we observe stress\novershoot corresponding to network yielding. Upon yielding, cage breaking results in a significant decrease in\nthe chain relaxation time, which is reflected in the enhanced chain diffusivity relative to the quiescent state.\nBelow a crit. shear rate and upon yielding, we observe the formation of steady-state shear bands in the\ngradient direction that have a marked difference in the polymer concn. and are dynamically and structurally\ndistinct.", "publisher": "Caltech Library", "publication_date": "2015-08" }, { "id": "authors:t3eg7-0va54", "collection": "authors", "collection_id": "t3eg7-0va54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131011-083218067", "type": "conference_item", "title": "Electrostatic effects in macromolecular and interfacial systems", "author": [ { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" } ], "abstract": "In this talk, I discuss two electrostatic effects that have profound effects in macromol. and interfacial systems and yet\nhave not been much appreciated in the main literature on electrolytes or polyelectrolytes. The first effect is the Born solvation\nenergy or more generally the self-energy of salt ions. The preference of an ion to be solvated by the more polarizable\ncomponent in a liq. mixt. creates a significant driving force for phase sepn. and is responsible for the nonuniform salt concn. and\ncharge sepn. near an interface. The preferential solvation effect is used to explain the dramatic increase in the order-disorder\ntransition temp. of Polyethylene Oxide-Polystyrene diblock copolymer upon the addn. of small amts. of lithium salts. I also\npresent a simple theory for explaining the long-standing Jones-Ray and ion size effects in the interfacial tension for electrolyte\nsolns. The second effect is the Donnan potential effect in biol. systems. The presence of mostly neg. charged macromols. in\nthe cellular milieu generates a substantial neg. potential relative to a monovalent salt soln. I present a theory that argues that\nthis Donnan potential explains the prevalence of neg. overcharged RNA viruses in Nature.", "publisher": "Caltech Library", "publication_date": "2013-09" }, { "id": "authors:s2mt4-pca18", "collection": "authors", "collection_id": "s2mt4-pca18", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130715-084014607", "type": "conference_item", "title": "Effects of Image Charges on Double Layer Structure and Forces", "author": [ { "family_name": "Wang", "given_name": "Rui", "clpid": "Wang-Rui" }, { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" } ], "abstract": "The study of the electrical double layer lies at the heart of soft matter physics and biophysics. Here, we address the effects of\nthe image charges on the double layer structure and forces using a weak coupling theory. For electrolyte solutions between\ntwo neutral plates, we show that depletion of the salt ions by the image charge repulsion results in short-range attractive and\nlong-range repulsive forces. If cations and anions are of different valency, the asymmetric depletion leads to the formation of\nan induced electrical double layer. In comparison to a 1:1 electrolyte solution, both the attractive and the repulsive parts of the\ninteraction are stronger for the 2:1 electrolyte solution. For two charged plates, the competition between the surface charge\nand the image charge effect can give rise to like-charge attraction and charge inversion. These results are in stark contrast\nwith predictions from the Poisson-Boltzmann theory.", "publisher": "Caltech Library", "publication_date": "2013-06" } ]