In Situ X-ray Diffraction Study of Layered Li–Ni–Mn–Co Oxides: Effect of Particle Size and Structural Stability of Core–Shell Materials
Bibliographic record
Abstract
Lithium-rich Li[Li x M 1– x ]O 2 (M = Ni, Mn, Co) materials have been claimed to be two phase by some researchers and to be one phase by others when all the available lithium is extracted electrochemically. To clear up this confusion, the Li-rich samples [Li[Li 0.12 (Ni 0.5 Mn 0.5 ) 0.88 ]O 2 and Li[Li 0.23 (Ni 0.2 Mn 0.8 ) 0.77 ]O 2 with different particle sizes were synthesized for in situ X-ray diffraction experiments. In situ X-ray diffraction measurements revealed two-phase behavior of 10 μm particles and one-phase behavior for samples with submicrometer particles. The phase separation in samples with large particles agrees with literature proposals of oxygen release from a surface layer and the observation of distinct surface and bulk phases. The small particle samples are so small that they are entirely composed of the surface phase found in the large particle samples. These results strongly suggest that the size of particles can significantly affect the structural evolution testing and electrochemical performance of the Li- and Mn-rich materials. It is proposed that the surface phase continuously grows during charge–discharge cycling, which leads to voltage fade in large particle samples. Meanwhile, in situ X-ray diffraction measurements were also performed for the layered Li–Ni–Mn–Co oxides with varying nickel contents, including NMC811 (LiNi 0.8 Mn 0.1 Co 0.1 O 2 ), NMC442 (LiNi 0.42 Mn 0.42 Co 0.16 O 2 ), [Li[Li 0.12 (Ni 0.5 Mn 0.5 ) 0.88 ]O 2, and Li[Li 0.23 (Ni 0.2 Mn 0.8 ) 0.77 ]O 2 . Samples with higher nickel content showed much faster contraction of unit cell volume as a function of cell voltage, which suggests that the core–shell structures with a nickel-rich core (e.g., NMC811) and a Mn-rich shell (e.g., Li 1.23 Ni 0.154 Mn 0.616 O 2 ) should not crack during charge–discharge cycling.
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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".