Ionics and Electrochemical Reactions in 1D and 3D Crosslinked Porous Electrodes

Lithium ion batteries are a critical component enabling many modern technologies, including portable electronics, hybrid electric vehicles and more. While interest in nanomaterials for lithium ion batteries has been growing in recent years, very few systematic studies have been carried out on controlled architectures to explore of the impact of nanoscale and mesoscale structure on the reaction mechanisms, kinetics and resulting rate performance in these electrodes. Here we utilize a combination of anodized aluminum oxide templates and atomic layer deposition to fabricate a variety of systematically variable electrode architectures. The structural control and electrode design are described in detail. Then, analysis of the rate performance, with a focus on distinguishing between diffusion and charge transfer limited reaction mechanisms, is carried out for two distinct electrode systems, focusing on different issues which face advanced electrode architectures. First, we analyze the impact of nanotube length in 1D structures to establish a quantitative understanding of the balance between the loss of capacity due to resistance increases and improvements due to surface area increases. Second, we analyze the impact of transitioning from arrays of 1D nanostructures to crosslinked electrode networks. While 1D alignment is often considered favorable for reducing defects that may lead to capacity loss and degradation, our results indicate that the 3D structures gain more from increased surface area and mass loading than they lose from the introduction of defects. This observation opens up opportunities for rationally designed advanced electrode architectures to optimize the performance of electrochemical energy storage devices in novel ways that are unavailable to conventional, particle based electrode configurations

Pascalammetry with operando microbattery probes: Sensing high stress in solid-state batteries.

Energy storage science calls for techniques to elucidate ion transport over a range of conditions and scales. We introduce a new technique, pascalammetry, in which stress is applied to a solid-state electrochemical device and induced faradaic current transients are measured and analyzed. Stress-step pascalammetry measurements are performed on operando microbattery probes (Li2O/Li/W) and Si cathodes, revealing stress-assisted Li+ diffusion. We show how non-Cottrellian lithium diffusional kinetics indicates stress, a prelude to battery degradation. An analytical solution to a diffusion/activation equation describes this stress signature, with spatiotemporal characteristics distinct from Cottrell's classic solution for unstressed systems. These findings create an unprecedented opportunity for quantitative detection of stress in solid-state batteries through the current signature. Generally, pascalammetry offers a powerful new approach to study stress-related phenomena in any solid-state electrochemical system

Nurses Alumni Association Bulletin, Fall 1995

1995-1996 Meeting Dates Calendar 1996 Annual Luncheon-Meeting Notice Officers and Committee Chairs Bulletin Publication Committee 1995-1996 Meeting Dates Calendar The President\u27s Message Financial Report What\u27s New Fiftieth Anniversary Resume of Minutes of Alumni Association Meetings Scholarship Funds at Work CAHS Alumni Board/Diploma School Alumni Office News Jefferson Health System Oldest Veteran Dies 1OOth Anniversary Pearl Harbor Remembered Memories Janet Hindson Retires Happy Birthday Scholarship Fund donors for 1994 Committee Reports By-Laws Development Bulletin Relief Fund Satellite Social Scholarship In Memoriam, Names of Deceased Graduates Class News Luncheon Photos Jefferson Alumni Identification Card The Diploma School of Nursing Alumni Association-Mabel C. Prevost Letter of Appreciation Tribute To a Mother An End Must Come Stuff For Senior Citizens to Chuckle Over Membership Application Relief Fund Application To Order: A Chronological History and Alumni Directory From TJU Bookstore Scholarship Fund Application Pins, Transcripts, Class Address List, Change of Address Forms, Alumni Identification Card Campus Map Picture - Class of 1893-189

Probing Porous Structure of Single Manganese Oxide Mesorods with Ionic Current

Characterization of materials in confined spaces, rather than attempting to extrapolate from bulk material behavior, requires the development of new measurement techniques. In particular, measurements of individual meso- or nanoscale objects can provide information about their structure which is unavailable by other means. In this report, we perform measurements of ion currents through a few hundred nanometer long MnO₂ rods deposited in single polymer pores. The recorded current confirms an existence of a meshlike character of the MnO₂ structure and probes the effective size of the mesh voids and the polarity of surface charges. The recorded ion current through deposited MnO₂ structure also suggests that the signal is mostly due to metal cations and not to protons. This is the first time that ionic current measurements have been used to characterize mesoporous structure of this important electrode material

Natural Cellulose Fiber as Substrate for Supercapacitor

Cellulose fibers with porous structure and electrolyte absorption properties are considered to be a good potential substrate for the deposition of energy material for energy storage devices. Unlike traditional substrates, such as gold or stainless steel, paper prepared from cellulose fibers in this study not only functions as a substrate with large surface area but also acts as an interior electrolyte reservoir, where electrolyte can be absorbed much in the cellulose fibers and is ready to diffuse into an energy storage material. We demonstrated the value of this internal electrolyte reservoir by comparing a series of hierarchical hybrid supercapacitor electrodes based on homemade cellulose paper or polyester textile integrated with carbon nanotubes (CNTs) by simple solution dip and electrodeposited with MnO₂. Atomic layer deposition of Al₂O₃ onto the fiber surface was used to limit electrolyte absorption into the fibers for comparison. Configurations designed with different numbers of ion diffusion pathways were compared to show that cellulose fibers in paper can act as a good interior electrolyte reservoir and provide an effective pathway for ion transport facilitation. Further optimization using an additional CNT coating resulted in an electrode of paper/CNTs/MnO₂/CNTs, which has dual ion diffusion and electron transfer pathways and demonstrated superior supercapacitive performance. This paper highlights the merits of the mesoporous cellulose fibers as substrates for supercapacitor electrodes, in which the water-swelling effect of the cellulose fibers can absorb electrolyte, and the mesoporous internal structure of the fibers can provide channels for ions to diffuse to the electrochemical energy storage materials

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The Power of Sunspots: An Experimental Analysis

We present an experiment in which extrinsic signals may generate sunspot equilibria. The game has a unique symmetric non-sunspot equilibrium, which is also risk dominant. Other equilibria can be ordered according to risk dominance. By comparing treatments with different information structure, we measure the force of extrinsic signals. Results indicate that Sunspot equilibria emerge naturally, if there are salient (but extrinsic) public signals. However, salient private signals of high precision may also cause sunspot-like behavior even though this is no equilibrium. The higher the precision of signals and the easier they can be aggregated, the more powerful they are in dragging behavior away from the risk dominant to risk dominated strategies