A study of the relationship between lithium ion transport and structure and dynamic behavior in polyethylene oxide-melt/LiClO<sub>4</sub> battery electrolytes.
Notice bibliographique
Résumé
An experimental study of the canonical SPE (“solid” polymer electrolyte) for rechargeable “rocking chair” lithium/polymer batteries, viz. LiClO4 dissolved in molten poly(ethylene oxide) (PEO), was carried out under DOE grant FG02-04ER15573. In this study, an improved understanding was obtained of the relationship between lithium ion transport and polymer behavior in these SPEs. Among other applications, these sturdy temperature-tolerant and powerful light-weight batteries would be used in electric and electric-hybrid vehicles to reduce greenhouse gas emissions, to store unused electrical energy for peak demand loads and as compact, light-weight energy sources for aircraft and spacecraft. During the period of the grant, the American/Canadian partnership company “Avestor” fabricated and successfully demonstrated a telecommunications application of shoe-box sized batteries and representatives from Avestor visited our research lab at UNLV. They found our results interesting and relevant to their work and invited us to visit Avestor and present a talk about our efforts at UNLV. Unfortunately Avestor (who was scheduled to build a battery production facility in Apex, Nevada just North of Las Vegas) folded before the visit could be made. In the grant work, two well characterized PEO samples having molar masses distinctly below and distinctly above the melt entanglement molar mass were used and three laser light scattering techniques employed as the principal noninvasive methods of investigating liquid poly(ethylene oxide) (PEO)/LiClO4 SPEs. These investigations considered the effects of temperature, dissolved salt concentration and scattering wavevector on SPE behavior. Classical or “static” light scattering and the dynamic light scattering techniques of photon correlation spectroscopy (PCS) and Fabry-Perot interferometry (FPI) were used to study SPE static, low frequency and high frequency dynamic behaviors, respectively. Static measurements provided information about system structure while low frequency results provided information about slower (0.1-10s) more global behavior and high frequency results provided information about faster (~10-11s) more local behavior. In addition, viscometry, rheometry and thermal analysis provided vital complementary results. It was found that liquid PEO/lithium salt solutions for both PEO molar masses are random transient physical networks with measureable network and intra-network relaxation times using PCS and FPI. Thus novel and informative results addressing both large scale and small scale behavior were obtained. For example, the high sensitivity of liquid PEO electrolytes to the presence of presumably undesirable trace amounts of residual water and/or methanol was clearly evident in PCS measurements. In “unentangled” melts the activation energies for diffusive relaxation in liquid PEO/lithium salt electrolytes measured using PCS and the activation energies for viscous flow in these systems determined by viscometry were identical while thermal analyses detected no phase transitions for these systems. These results reinforced an earlier assumption that the liquid PEO/LiClO4 system is a liquid polymer “bimorph” (to our knowledge the first of its kind to be reported) with the network comprising one form of the polymer while the second form corresponds to that of a viscous damping liquid. At a given temperature, FPI characteristic relaxation times for local, between-chain motions were consistent with PCS results so that increases with increasing salt concentration were accompanied by increases in the elastic modulus and corresponding increases in system stiffness. Note that corresponding decreases in polymer segmental mobility are accompanied by reduced ion diffusivity. For entangled melts, PCS network relaxations were again observed and these systems were also considered to be bimorphs even though diffusion activation energies were distinctly larger than viscous flow activation energies - a difference attributed to the effects of entanglement. Moreover, SLS measurements revealed entangled melts to be “percolation gels” with a measured fractal dimension of about 2 and static correlation lengths that increased gradually from about 500 nm to about 700 nm with increasing salt concentration. Meanwhile, rheological measurements found these polymer/salt melts to behave simply as liquids. FPI measurements have not yet been made on these entangled PEO melts.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,000 |
| Études des sciences et des technologies | 0,000 | 0,000 |
| Communication savante | 0,000 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».