Improving lithium-ion battery safety through separators with thermal shutdown characteristics induced by thermal expansion microspheres
Bibliographic record
Abstract
Battery separators with thermal shutdown capabilities have been developed to improve battery safety. The developed separators incorporate thermally expansive microspheres and have been produced based on poly(vinylidene fluoride-co-hexafluoropropylene), PVDF-HFP, with different amounts (0 wt%, 5 wt%, 10 wt% and 15 wt%) of thermally expansive microspheres. The preparation of the separators involves solvent casting with thermally induced phase separation at different temperatures: 20 °C and 80 °C. The processing conditions allow to tune membranes degree of porosity between 54 % and 5 % depending on the microspheres content. Further, microspheres addition leads to a decrease in the Young modulus from 474 MPa for neat PVDF-HFP membranes to 365 MPa for the membrane with 15 wt% of microspheres. The PVDF-HFP membrane with 15 wt% microsphere content and evaporated at room temperature shows values of 84 %, 0.08 mS cm −1 , 0.37, 2.7, and 145 and for electrolyte uptake, ionic conductivity, lithium transference number, tortuosity, and MacMullin number, respectively. In a half-cell Li/C–LiFePO 4 , the electrochemical performance of these separators shows reversible cyclability and suitable rate capability with discharge capacity value of 146 mAh.g −1 at C/8-rate. After 100 cycles, the PVDF-HFP membrane with 15 wt% microsphere content shows a capacity value of 44 mAh.g −1 at C-rate, with a 5 % capacity fading and a ∼100 % coulomb efficiency. The thermal shutdown capabilities were verified in charge-discharge tests with applied temperature. The thermal shutdown effect is confirmed at 100 °C, temperature at which the microspheres increase in size and collapse the structure of the separator, decreasing battery discharge capacity (C/5-rate) from 120 mAh.g −1 to 0 mAh.g −1 . The presented approach allows to improve battery safety by properly addressing thermal runaway. • Battery thermal shutdown has been implemented in separator membranes. • Thermal shutdown is achieved through the expansion of microspheres. • These separators are based on PVDF-HFP with different amounts of microspheres. • PVDF-HFP/15 wt% of microspheres show excellent cycling behavior and thermal shutdown.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 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 teacher head, 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".