Insights into Mg<sup>2+</sup> Intercalation in a Zero-Strain Material: Thiospinel Mg<sub><i>x</i></sub>Zr<sub>2</sub>S<sub>4</sub>
Bibliographic record
Abstract
The Mg battery cathode material, thiospinel Mg x Zr 2 S 4 (0 ≤ x ≤ 1), exhibits negligible volume change (ca. 0.05%) during electrochemical cycling, providing valuable insight into the limiting factors in divalent cation intercalation. Rietveld refinement of XRD data for Mg x Zr 2 S 4 electrodes at various states of charge,, coupled with EDX analysis, demonstrates that Mg 2+ can be inserted into Zr 2 S 4 at 60 °C up to x = 0.7 at a C/10 rate (up to x = 0.9 at very slow rates) and cycled with a high Coulombic efficiency of 99.75%. HAADF-STEM studies provide clear visual evidence of Mg-ion occupation in the lattice, whereas XAS studies show that Zr 4+ was reduced upon Mg 2+ intercalation. Operando and synchrotron XRD studies reveal the creation of two phases during the latter stages of discharge ( x > 0.5) as the lattice fills and Mg 2+ ions begin occupying tetrahedral (8a) sites in addition to octahedral (16c) interstitial sites. Compared to the isostructural Ti 2 S 4 thiospinel, Zr 2 S 4 presents a slightly larger cell volume and hence an almost ideal zero-strain lattice on Mg 2+ insertion. Nonetheless, its 4-fold lower electronic conductivity results in a diffusion coefficient for Mg 2+ ions ( D Mg; 1 × 10 –10 to 1 × 10 –9 cm 2 /s) that is more than a factor of 10 lower than in Ti 2 S 4 . This shows that delocalization of the electron charge carriers in the framework is a very important factor in governing multivalent ion diffusivity in the thiospinel framework and, by extension, in other materials.
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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".