Formation of Mn-Zn Layered Double Hydroxide - New Insights into the Charge Storage Mechanism of Near-Neutral MnO<sub>2</sub>/Zn Batteries
Bibliographic record
Abstract
A relatively new type of aqueous battery that is based on MnO2/Zn chemistry in near-neutral pH electrolytes is receiving significant attention in the research community for its potential commercial applications. This chemistry offers many advantages such as relatively high cycle life [1], low cost, high natural abundance and availability of the active materials, and environmental friendliness. On the other hand, issues with the formation of parasitic Zn-layered double hydroxide (ZnLDH) creates challenges for the capacity utilization in high mass loading electrodes. Revealing the charge storage mechanism and the products of the discharge reaction would significantly help with the scaling up of this technology. At present, there is a debate on the nature of the reaction mechanism considering proton or zinc intercalation (or co-insertion of both) into the MnO2 structure, and what structural transformations occur during charge/discharge. We present new insights on the reaction mechanism and show that novel, not reported yet, Mn-Zn based layered double hydroxide (MnZnLDH, MnxZny(OH)zSO4 · 5H2O) forms during the first discharge reaction (Figure 1) [2]. MnZnLDH forms through a conversion reaction that occurs between MnO2 and Zn2+ during the first discharge plateau and it is a structural analogue of ZnLDH. Electrochemical experiments in different aqueous/organic electrolytes with and without the presence of Zn ions have shown that protons and water play significant roles in the charge-storage mechanism, while Zn ions form species at the surface rather than intercalating in the bulk of MnO2 structure. Excellent rechargeability was achieved for the ramsdellite (MnO2) and hausmannite (Mn3O4) phases, i.e., over 1000 [1] and 800 [3] cycles, respectively, without considering the formation of MnZnLDH. However, improving the reversibility of MnZnLDH transformation during the cycling will enhance the battery cycle life even further. References [1] I. Stoševski, A. Bonakdarpour, F. Cuadra, & D. P. Wilkinson, Chem. Comm., 2019, 55, 2082-2085. [2] I. Stoševski, A. Bonakdarpour, B. Fang, P. Lo, & D. P. Wilkinson, Electrochim. Acta, 2021, 390, 138852. [3] I. Stoševski, A. Bonakdarpour, B. Fang, S. T. Voon, & D. P. Wilkinson, Int. J. Energy Res., 2021, 45, 220-230. Figure 1. Mechanism of the first discharge reaction Figure 1
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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 | 0.001 |
| 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".