Structural View of Li Ion and Electron Correlation in Li<sub>2</sub>FeSiO<sub>4</sub> Cathode
Bibliographic record
Abstract
Orthosilicates, Li2 M SiO4, where M = Fe, Mn, Co, Ni, are characterized by a theoretical specific capacity that is twice that of LiFePO4, namely 340 vs. 170 mAh/g. In this presentation, we have probed the structural evolution and charge compensation of Li2FeSiO4 cathode using both in-situ/postmortem synchrotron XRD/XANES and first-principle calculations1-3. The results demonstrate that the formation of Li-Fe antisite defects play a key role in destabilizing the Li2FeSiO4 structure and “catalyzing” the monoclinic-to-orthorhombic transition. Then the charge compensation for the first Li extraction does not come solely from the ferrous to ferric conversion due to the strong electron correlation of Fe 3d orbitals, but interestingly from prominent participation of lattice oxygen as well that appears to destabilize the cycled structure. Using scanning transmission X-ray microscopy, it is revealed that the electrochemical lithiation/delithiation of Li2FeSiO4 electrode does not proceed uniformly but it exhibits an unusual solid solution pattern4 with the stored Li content varying locally possibly arising from a combination of inherent LFS material and electrode properties like poor conductivities, variable particle size/distribution and extent of electrolyte penetration. All these findings should have a thought-provoking influence on the study of the material itself and the broader Li-ion battery research community as well. References 1. Lu, X.; Wei, H. J.; Chiu, H. C.; Gauvin, R.; Hovington, P.; Guerfi, A.; Zaghib, K.; Demopoulos, G. P. Rate-dependent phase transitions in Li2FeSiO4 cathode nanocrystals. Sci Rep-Uk 2015, 5, 8599. 2. Arthur, Z.; Chiu, H.-C.; Lu, X.; Chen, N.; Emond, V.; Zaghib, K.; Jiang, D.-T.; Demopoulos, G. P. Spontaneous reaction between uncharged lithium iron silicate cathode and LiPF6-based electrolyte Chem Commun 2015, accpeted, DOI: 10.1039/C5CC07197F. 3. Lu, X.; Chiu, H.-C.; Bevan, H. K.; Jiang, D.-T.; Zaghib, K.; Demopoulos, P. G. Density functional theory insight into the structure stability and Li diffusion properties of monoclinic and orthorhombic Li2FeSiO4 cathodes. J Power Sources 2015, In revision. 4. Lu, X.; Chiu, H.-C.; Arthur, Z.; Zhou, J. G.; Wang, J.; Chen, N.; Jiang, D.-T.; Zaghib, K.; Demopoulos, G. P. Quasi-equilibrium Li storage in metastable Li2FeSiO4 cathode. 2015, Under review.
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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) | 0.002 | 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".