{
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      "id": "thermal-propagation",
      "name": "Thermal propagation",
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      "definition": "Thermal runaway spreading from one cell to its neighbours through conducted heat, hot gas and flame. Pack designs are judged by whether, and how slowly, a single failing cell takes the rest with it.",
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        "lede": "How cells fail dangerously, how that is tested, and what is built in to stop it.",
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        "lesson_url": "https://lemonergy.com/learn/fundamentals/battery-aging/",
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        "section": "topic-safety",
        "definition": "An insulating sheet — aerogel, mica, ceramic fibre or intumescent material — placed between cells or modules to slow heat transfer during a thermal event and buy time for occupants to leave.",
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      "label": "Thermal propagation test",
      "properties": {
        "id": "propagation-test",
        "name": "Thermal propagation test",
        "section": "topic-safety",
        "definition": "Triggering thermal runaway in one cell of a module or pack — by heater, nail or overcharge — and measuring whether and how fast it spreads. Regulations now require at least a warning period, five minutes in several markets, before the cabin is at risk.",
        "related": [
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      "id": "reference:feng-runaway",
      "type": "Reference",
      "label": "Thermal runaway mechanism of lithium ion battery for electric vehicles: A review",
      "properties": {
        "title": "Thermal runaway mechanism of lithium ion battery for electric vehicles: A review",
        "publisher": "Energy Storage Materials",
        "url": "https://doi.org/10.1016/j.ensm.2017.05.013",
        "type": "Review article",
        "scope": "Electrical, mechanical and thermal abuse; thermal-runaway mechanisms and propagation.",
        "year": 2018,
        "authors": [
          "Xuning Feng et al."
        ],
        "accessed": "2026-10-27"
      }
    }
  ]
}