Neutral pH Ion-Conducting Polymer Electrolytes for Solid-state Electrochemical Capacitors
Bibliographic record
Abstract
Thin, solid, flexible, safe, and reliable electrochemical capacitors (ECs) are in demand to power up next generations of wearable electronics and Internet-of-Things devices. Polymer electrolytes are key enablers for the development of solid-state capacitive devices. In this thesis, neutral pH ion-conducting polymer electrolytes (NPPEs) have been developed for ECs using either Li2SO4 or Na2SO4 ionic conductor and polyacrylamide (PAM) host. The optimized NPPEs exhibit: (i) wide electrochemical stability window, (ii) high ionic conductivity with low activation energy for conduction, (iii) long-shelf-life, (iv) good interfaces with EDLC electrodes, and (v) wide-range thermal stability. An in-depth investigation on material properties affecting electrolyte performance has been conducted for NPPEs. Through correlative studies between vibrational spectroscopic and electrochemical measurements, ion hydration was determined as crucial factor affecting ion conductivity and performance stability. Fully solvated ions are necessary to maintain stable performance over time, while smaller hydration shell allows for fast ion mobility. Meanwhile, at low temperatures below freezing point, EDLC interface can only be maintained with NPPE containing fewer crystallized water. Anti-icing additives possessing deep eutectic properties with water, e.g., DMSO, can widen the lower limit of operating temperatures of the NPPE. These correlations are essential considerations for developing future generations of NPPE. In carbon-based solid EDLC devices, both Li2SO4-PAM and Na2SO4-PAM demonstrated a stable 1.8 V cell voltage, much wider than those cells with proton- or hydroxide-ion based electrolytes which allows for significantly higher energy and power densities. Adding DMSO, the ternary system enabled the operating temperature of solid EDLC cells to -20 °C, beyond the typical limit in most aqueous-based systems. The effects of carbon loading on NPPE-based EDLCs were studied using two types of carbon with different pore structures to understand the limitations in designing solid capacitive devices. Although increasing carbon loading leads to higher capacitance, there are two possible adverse effects: (1) lower electrolyte penetration from highly viscous NPPE precursor solution; and (2) increased diffusion limitation, leading to lower material utilization which can be aggravated at faster rates, low temperatures, or with closed micropore-rich materials. These insights can be added to the guiding principle for design and develop solid EDLCs.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.001 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".