Understanding the Self-Discharge Redox Shuttle Mechanism of Dimethyl Terephthalate in Lithium-Ion Batteries
Bibliographic record
Abstract
Recent studies showed that LFP/graphite cells without additives show higher reversible self-discharge after 500 h of open-circuit voltage (OCV) storage at 40 or 60°C than NMC811/graphite cells.1 Furthermore, cells with lithium hexafluorophosphate (LiPF6), the most commonly used conducting salt in lithium-ion batteries, show higher self-discharge than cells with lithium bis(fluorosulfonyl)imide (LiFSI), an alternative salt with higher temperature stability.2 Recently, dimethyl terephthalate (DMT) was identified as the redox shuttle molecule responsible for the unwanted self-discharge of these lithium-ion batteries.3 In a lithium-ion cell, a reversible shuttle can gain an electron at the negative electrode by reduction, diffuse to the positive electrode, lose the electron by oxidation, and then repeat the process many times (see Figure 1). Adamson et al.4 proved that DMT is created in-situ as a breakdown product of polyethylene terephthalate (PET), which is a surprisingly common polymer for the adhesive tapes found in commercial batteries. The exact redox potential and electrochemical stability of DMT, as well as its shuttling mechanism across electrodes passivated with a solid-electrolyte interphase (SEI) however were not understood. Based on an optimized coin cell cyclic voltammetry setup, ultra high precision coulometry measurements, OCV storage, and GC-MS experiments, we present new insights on the self-discharge redox shuttle mechanism of DMT in LFP/graphite pouch cells, investigate if this redox shuttle can account for the self-discharge differences in LiPF6 and LiFSI cells, and explore the stability of DMT in pouch cells. References: E. R. Logan, A. Eldesoky, E. Eastwood, H. Hebecker, C. P. Aiken, M. Metzger and J. R. Dahn, J Electrochem Soc, 2022, 169, 040560. E. R. Logan, A. Eldesoky, E. Eastwood, H. Hebecker, C. P. Aiken, M. Metzger and J. R. Dahn, J Electrochem Soc, 2022, 169, 040560. S. Buechele, A. Adamson, A. Eldesoky, T. Boetticher, L. Hartmann, T. Boulanger, S. Azam, M. B. Johnson, T. Taskovic, E. Logan and M. Metzger, J Electrochem Soc, 2023, 170, 010511. A. Adamson, T. Bötticher, K. Tuul, M. Garayt, S. Azam and M. Metzger, Manuscript in Preparation, 2023. 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) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.003 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".