Assessment of critical biological resources, La Plata County, Colorado

Prepared for: La Plata County, Durango, Colorado.Includes bibliographical references

Conjugated Imine Polymer Synthesized via Step-Growth Metathesis for Highly Stable Silicon Nanoparticle Anodes in Lithium-Ion Batteries

This work reports a new method to synthesize polyphenylmethanimine (polyPMI) as a linear or a hyperbranched, conjugated polymer using an aldehyde-imine metathesis reaction. This work details the reaction mechanisms of this polymerization by characterizing a red-shift in its absorption spectrum as polymer conjugation length increases and verifies that this optical shift results from extended π-condensation using density functional theory. This new synthetic approach provides a polymer that can potentially be depolymerized for facile recyclability and is compatible with air- and water-sensitive chemistries. As an example of the utility of this new approach, this work demonstrates that this polymer can be directly grown on silicon nanoparticles to create silicon anodes for lithium-ion batteries with a high degree of electrochemical interfacial passivation. These silicon anodes exhibit Coulombic efficiencies above 99.9% and can accommodate silicon nanoparticle expansion and contraction during lithiation and delithiation as demonstrated by stable reversible capacities for 500 cycles. Finally, this work demonstrates that polyPMI facilitates the formation of a lithium fluoride rich solid electrolyte interphase that remains chemically and mechanically stable after long term cycling

Characterizing Solid Electrolyte Interphase on Sn Anode in Lithium Ion Battery

Tin (Sn) nanoparticle electrodes have been prepared and battery cycling performance has been investigated with 1.2 M LiPF6 in ethylene carbonate (EC) / diethyl carbonate (DEC) electrolyte (1:1, w/w) with and without added vinylene carbonate (VC) or fluoroethylene carbonate (FEC). Incorporation of either VC or FEC improves the capacity retention of Sn nanoparticle electrodes although incorporation of VC also results in a significant increase in cell impedance. The best electrochemical performance was observed with electrolyte containing 10% of added FEC. In order to develop a better understanding of the role of the electrolyte in capacity retention and solid electrolyte interface (SEI) structure, ex-situ surface analysis has been performed on cycled electrodes with infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Hard XPS (HAXPES). The ex-situ analysis reveals a correlation between electrochemical performance, electrolyte composition, and SEI structure

Effect of Vinylene Carbonate and Fluoroethylene Carbonate on SEI Formation on Graphitic Anodes in Li-Ion Batteries

Binder free (BF) graphite electrodes were utilized to investigate the effect of electrolyte additives fluoroethylene carbonate (FEC) and vinylene carbonate (VC) on the structure of the solid electrolyte interface (SEI). The structure of the SEI has been investigated via ex-situ surface analysis including X-ray Photoelectron spectroscopy (XPS), Hard XPS (HAXPES), Infrared spectroscopy (IR) and transmission electron microscopy (TEM). The components of the SEI have been further investigated via nuclear magnetic resonance (NMR) spectroscopy of D2O extractions. The SEI generated on the BF-graphite anode with a standard electrolyte (1.2 M LiPF6 in ethylene carbonate (EC) / ethyl methyl carbonate (EMC), 3/7 (v/v)) is composed primarily of lithium alkyl carbonates (LAC) and LiF. Incorporation of VC (3% wt) results in the generation of a thinner SEI composed of Li2CO3, poly(VC), LAC, and LiF. Incorporation of VC inhibits the generation of LAC and LiF. Incorporation of FEC (3% wt) also results in the generation of a thinner SEI composed of Li2CO3, poly(FEC), LAC, and LiF. The concentration of poly(FEC) is lower than the concentration of poly(VC) and the generation of LAC is inhibited in the presence of FEC. The SEI appears to be a homogeneous film for all electrolytes investigated

Physiological Correlates of Volunteering

We review research on physiological correlates of volunteering, a neglected but promising research field. Some of these correlates seem to be causal factors influencing volunteering. Volunteers tend to have better physical health, both self-reported and expert-assessed, better mental health, and perform better on cognitive tasks. Research thus far has rarely examined neurological, neurochemical, hormonal, and genetic correlates of volunteering to any significant extent, especially controlling for other factors as potential confounds. Evolutionary theory and behavioral genetic research suggest the importance of such physiological factors in humans. Basically, many aspects of social relationships and social activities have effects on health (e.g., Newman and Roberts 2013; Uchino 2004), as the widely used biopsychosocial (BPS) model suggests (Institute of Medicine 2001). Studies of formal volunteering (FV), charitable giving, and altruistic behavior suggest that physiological characteristics are related to volunteering, including specific genes (such as oxytocin receptor [OXTR] genes, Arginine vasopressin receptor [AVPR] genes, dopamine D4 receptor [DRD4] genes, and 5-HTTLPR). We recommend that future research on physiological factors be extended to non-Western populations, focusing specifically on volunteering, and differentiating between different forms and types of volunteering and civic participation

X-Ray-Induced Changes to Passivation Layers of Lithium-Ion Battery Electrodes

The surface sensitivity available to photoelectron spectroscopies (PESs) makes them popular techniques for characterization of chemical environments at shallower depths than other, more bulk-sensitive techniques and because they are generally thought to be nondestructive. Variable energy, synchrotron radiation (SR), permits access to information not available to common lab-based radiation sources, making high-energy PES studies extremely useful for understanding thin films and interfaces. High-SR photon flux has been useful for developing models of soft X-ray-induced effects, but hard X-ray SR-induced effects are less well studied and will be increasingly important as popularity and availability of SR for thin film analysis continues to grow. We report here on observed modification of the solid electrolyte interphase of a lithium-ion battery electrode during prolonged exposure to 4 keV SR. The effects can be summarized by desorption of oxygen-containing species from the sample surface and by reactions within the film. Also presented is an estimate of the layer thickness’ time evolution during the prolonged SR exposure

Thermal stability of lithium-ion battery electrolytes

The thermal decomposition of LiPF6 in the solid state and as solutions in dialkylcarbonates has been investigated. The thermal decomposition of LiPF6 was investigated with differential scanning calorimatry (DSC) suggesting decomposition to LiF and PF5. In solution, PF5 reacts with dialkylcarbonates to form a variety of decomposition products including carbon dioxide (CO2), ethers (R2O), alkylfluorides (RF), phosphorus oxyfluoride (OPF3), and fluorophosphates (OPF2OR, OPF(OR)2). The structure of the decomposition products are supported by nuclear magnetic resonance (NMR) spectroscopy and gas chromatography with mass selective detection (GC-MS). © 2003 Elsevier Science B.V. All rights reserved

Additives for stabilizing LiPF6-based electrolytes against thermal decomposition

Thermal stability of lithium-ion battery electrolytes composed of LiPF 6 in a mixture of organic carbonates was probed. Generation of PF5 via the thermal dissociation of LiPF6 is the primary source of thermal decomposition. It was found that the addition of low concentrations (3-12%) of Lewis basic additives provides a dramatic increase in the thermal stability of the electrolyte. The increased stability is linked to the formation of base: PF5 complexes which reversibly sequester PF5, preventing the decomposition of the electrolyte. Lewis bases investigated include pyridine, hexamethoxycyclotriphosphazene, and hexamethylphosphoramide. Our results can serve as a valuable model for stabilizing organic electrolytes against thermal decomposition initiated by Lewis acids. © 2005 The Electrochemical Society. All rights reserved