Interrogation of the Reaction Mechanism in a Na–O<sub>2</sub> Battery Using <i>In Situ</i> Transmission Electron Microscopy
Bibliographic record
Abstract
Critical factors that govern the composition and morphology of discharge products are largely unknown for Na–O 2 batteries. Here we report a reversible oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) process in a sodium–oxygen battery observed using in situ environmental-transmission electron microscopy (TEM) experiment. The reaction mechanism and phase evolution are probed using in situ electron diffraction and TEM imaging. The reversible ORR and OER cycling lies upon the nanosized copper clusters that were formed in situ by sodiation of CuS. In situ electron diffraction revealed the formation of NaO 2 initially, which then disproportionated into orthorhombic and hexagonal Na 2 O 2 and O 2 . Na 2 O 2 was the major final ORR product that uniformly covered the whole wire-shape cathode. This uniform product morphology largely increased the application feasibility of Na–O 2 batteries in industry. In the following OER process, the Na 2 O 2 transformed to NaO 2, which resulted in volume expansion at first, and then the NaO 2 decomposed to sodium ions and O 2 gas. Galvanostatic charge/discharge profiles of CuS in real Na–O 2 cells revealed a maximum capacity over 3 mAh cm –2 with a discharge cutoff voltage of 1.8 V and high cycling stability. The nanosized copper catalyst plays a dominating role in controlling the morphology, chemical composition of discharge products, and reversibility of this Na–O 2 battery. Our finding shines light on the exploration of effective catalysts for the Na–O 2 battery.
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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 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
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".