Probing Electrochemically Induced Structural Evolution and Oxygen Redox Reactions in Layered Lithium Iridate
Bibliographic record
Abstract
In order to exploit electrochemical capacity beyond the traditionally utilized transition-metal redox reactions in lithium-metal-oxide cathode materials, it is necessary to understand the role that oxygen ions play in the charge compensation mechanisms, that is, to know the conditions triggering electron transfer on the oxygen ions and whether this transfer is correlated with battery capacity. Theoretical and experimental investigations of a model cathode material, Li-rich layered Li 2 IrO 3, have been performed to study the structural and electronic changes induced by electrochemical delithiation in a lithium-ion cell. First-principles density functional theory (DFT) calculations were used to compute the voltage profile of a Li/Li 2– x IrO 3 cell at various states of charge, and the results were in good agreement with electrochemical data. Electron energy loss spectroscopy (EELS), X-ray absorption near-edge spectroscopy (XANES), resonant/nonresonant X-ray emission spectroscopy (XES), and first-principles core-level spectra simulations using the Bethe–Salpeter Equation (BSE) approach were used to probe the change in oxygen electronic states over the x = 0–1.5 range. The correlated Ir M 3 -edge XANES and O K-edge XANES data provided evidence that oxygen hole states form during the early stage of delithiation at ∼3.5 V because of the interaction between O p and Ir d states, with Ir-oxidation being the dominant source of electrochemical capacity. At higher potentials, the charge capacity was predominantly attributed to oxidation of the O 2– ions. It is argued that the emergence of oxygen holes alone is not necessarily indicative of electrochemical capacity beyond transition-metal oxidation because oxygen hole states can appear as a result of enhanced mixing of O p and Ir d states. Prevailing mechanisms accounting for the oxygen redox mechanism in Li-rich materials were examined by theoretical and experimental X-ray spectroscopy; however, no unambiguous spectroscopic signatures of oxygen dimer interactions or nonbonding oxygen states were identified.
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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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".