{
  "node": {
    "id": "term:hydrofluoric-acid",
    "type": "Term",
    "label": "Hydrofluoric acid",
    "properties": {
      "id": "hydrofluoric-acid",
      "name": "Hydrofluoric acid",
      "abbr": "HF",
      "section": "topic-safety",
      "definition": "Formed when LiPF₆ electrolyte meets water, or when a fluorinated cell burns. Inside a cell traces of it attack the positive electrode and SEI; in a fire it is the most dangerous component of the vented gas.",
      "related": [
        "lithium-salt",
        "off-gas",
        "transition-metal-dissolution",
        "dry-room"
      ],
      "url": "https://lemonergy.com/learn/glossary/hydrofluoric-acid/",
      "mentions": [
        "electrode",
        "positive-electrode",
        "electrolyte",
        "sei",
        "lipf6"
      ]
    }
  },
  "edges": [
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      "id": "edge:1782",
      "source": "term:hydrofluoric-acid",
      "target": "topic:topic-safety",
      "type": "belongsTo",
      "properties": {
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    {
      "id": "edge:1783",
      "source": "term:hydrofluoric-acid",
      "target": "term:lithium-salt",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:1784",
      "source": "term:hydrofluoric-acid",
      "target": "term:off-gas",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:1785",
      "source": "term:hydrofluoric-acid",
      "target": "term:transition-metal-dissolution",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:1786",
      "source": "term:hydrofluoric-acid",
      "target": "term:dry-room",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
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      "id": "edge:mentions/hydrofluoric-acid/electrode",
      "source": "term:hydrofluoric-acid",
      "target": "term:electrode",
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      "id": "edge:mentions/hydrofluoric-acid/positive-electrode",
      "source": "term:hydrofluoric-acid",
      "target": "term:positive-electrode",
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        "sourceFile": "terms.json",
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      "id": "edge:mentions/hydrofluoric-acid/electrolyte",
      "source": "term:hydrofluoric-acid",
      "target": "term:electrolyte",
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      "id": "edge:mentions/hydrofluoric-acid/sei",
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      "target": "term:sei",
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        "sourceFile": "terms.json",
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        "meaning": "Text mention; not a causal claim"
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      "id": "edge:mentions/hydrofluoric-acid/lipf6",
      "source": "term:hydrofluoric-acid",
      "target": "term:lipf6",
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        "sourceFile": "terms.json",
        "method": "build_glossary.mention_index + mentions",
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      "id": "topic:topic-safety",
      "type": "Topic",
      "label": "Safety and abuse",
      "properties": {
        "id": "topic-safety",
        "name": "Safety and abuse",
        "lede": "How cells fail dangerously, how that is tested, and what is built in to stop it.",
        "context": "Connect mechanisms with appropriate test evidence.",
        "example": "A low normal-load temperature does not demonstrate thermal-runaway containment.",
        "lesson_url": "https://lemonergy.com/learn/fundamentals/battery-aging/",
        "lesson_label": "Open degradation mechanisms"
      }
    },
    {
      "id": "term:lithium-salt",
      "type": "Term",
      "label": "Lithium salt",
      "properties": {
        "id": "lithium-salt",
        "name": "Lithium salt",
        "aka": [
          "LiPF₆",
          "LiFSI"
        ],
        "section": "topic-electrolytes",
        "definition": "The dissolved salt that supplies the mobile lithium ions in a liquid electrolyte, almost always lithium hexafluorophosphate, LiPF₆, at about one mole per litre. It reacts with traces of water to form hydrofluoric acid, which is why cells are filled in a dry room.",
        "related": [
          "electrolyte",
          "carbonate-solvent",
          "dry-room",
          "hydrofluoric-acid"
        ],
        "url": "https://lemonergy.com/learn/glossary/lithium-salt/",
        "mentions": [
          "lipf6"
        ]
      }
    },
    {
      "id": "term:off-gas",
      "type": "Term",
      "label": "Off-gas",
      "properties": {
        "id": "off-gas",
        "name": "Off-gas",
        "aka": [
          "vent gas"
        ],
        "section": "topic-safety",
        "definition": "The mixture released when a cell vents: electrolyte vapour, hydrogen, carbon monoxide, carbon dioxide and hydrocarbons, with hydrogen fluoride. It is flammable and toxic, and gas sensors detect it before smoke or heat in a storage container.",
        "related": [
          "venting",
          "hydrofluoric-acid",
          "gas-detection",
          "thermal-runaway"
        ],
        "url": "https://lemonergy.com/learn/glossary/off-gas/",
        "mentions": [
          "electrolyte"
        ]
      }
    },
    {
      "id": "term:transition-metal-dissolution",
      "type": "Term",
      "label": "Transition-metal dissolution",
      "properties": {
        "id": "transition-metal-dissolution",
        "name": "Transition-metal dissolution",
        "section": "topic-aging",
        "definition": "Manganese, nickel or cobalt ions leaching from the positive electrode into the electrolyte, especially at high voltage and temperature or when HF is present. They migrate to the negative electrode and poison the SEI there, accelerating lithium loss.",
        "related": [
          "lmo",
          "hydrofluoric-acid",
          "sei",
          "loss-of-active-material",
          "crosstalk"
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        "lesson": "fundamentals/battery-aging/#crystals",
        "url": "https://lemonergy.com/learn/glossary/transition-metal-dissolution/",
        "mentions": [
          "electrode",
          "negative-electrode",
          "positive-electrode",
          "electrolyte",
          "cobalt",
          "leaching",
          "manganese"
        ]
      }
    },
    {
      "id": "term:dry-room",
      "type": "Term",
      "label": "Dry room",
      "properties": {
        "id": "dry-room",
        "name": "Dry room",
        "section": "topic-manufacturing",
        "definition": "A production room whose air is kept extremely dry — dew points around −30 °C to −60 °C — so that no moisture reaches the cell while the electrolyte goes in. Water would react with the salt LiPF₆ to form hydrofluoric acid.",
        "related": [
          "dew-point",
          "vacuum-drying",
          "electrolyte-filling",
          "lithium-salt"
        ],
        "lesson": "fundamentals/cell-production/#assembly",
        "url": "https://lemonergy.com/learn/glossary/dry-room/",
        "mentions": [
          "electrolyte",
          "hydrofluoric-acid",
          "lipf6"
        ]
      }
    },
    {
      "id": "term:electrode",
      "type": "Term",
      "label": "Electrode",
      "properties": {
        "id": "electrode",
        "name": "Electrode",
        "section": "topic-components",
        "definition": "A solid conductor where the cell’s reaction happens, in contact with the electrolyte. A lithium-ion cell has a negative electrode and a positive electrode, each a porous coating on a metal foil.",
        "related": [
          "negative-electrode",
          "positive-electrode",
          "porous-electrode",
          "current-collector"
        ],
        "lesson": "fundamentals/cell-anatomy/#components",
        "example": {
          "title": "Two transport paths",
          "text": "Electrons need connected solid paths to the collector; ions need electrolyte paths to reaction sites. More of one constituent displaces others at fixed volume."
        },
        "url": "https://lemonergy.com/learn/glossary/electrode/",
        "mentions": [
          "electrolyte",
          "coating"
        ]
      }
    },
    {
      "id": "term:positive-electrode",
      "type": "Term",
      "label": "Positive electrode",
      "properties": {
        "id": "positive-electrode",
        "name": "Positive electrode",
        "section": "topic-components",
        "definition": "The electrode at the higher potential: a lithium metal oxide or phosphate coated on aluminium foil. It is the lithium source when a cell is built, and industry calls it the cathode.",
        "related": [
          "cathode",
          "cathode-active-material",
          "negative-electrode",
          "aluminium-foil"
        ],
        "lesson": "fundamentals/cell-anatomy/#anode-cathode",
        "example": {
          "title": "Polarity and reaction",
          "text": "The positive electrode retains its polarity label while its electrochemical reaction reverses between charge and discharge."
        },
        "url": "https://lemonergy.com/learn/glossary/positive-electrode/",
        "mentions": [
          "electrode"
        ]
      }
    },
    {
      "id": "term:electrolyte",
      "type": "Term",
      "label": "Electrolyte",
      "properties": {
        "id": "electrolyte",
        "name": "Electrolyte",
        "section": "topic-electrolytes",
        "definition": "The ion-conducting medium between the electrodes. In a liquid-electrolyte cell it fills the pores of both electrodes and the separator, so it is not a separate structural layer.",
        "related": [
          "lithium-salt",
          "carbonate-solvent",
          "electrolyte-additive",
          "ionic-conductivity",
          "solid-electrolyte",
          "ionic-liquid-electrolyte"
        ],
        "lesson": "fundamentals/cell-architecture/#electrolyte",
        "example": {
          "title": "Ions and electrons",
          "text": "Electrolyte carries ions between electrodes; the external circuit carries electrons. The two paths serve different roles."
        },
        "url": "https://lemonergy.com/learn/glossary/electrolyte/",
        "mentions": [
          "separator"
        ]
      }
    },
    {
      "id": "term:sei",
      "type": "Term",
      "label": "Solid–electrolyte interphase",
      "properties": {
        "id": "sei",
        "name": "Solid–electrolyte interphase",
        "abbr": "SEI",
        "section": "topic-aging",
        "definition": "A film of electrolyte reaction products on the negative-electrode particles — graphite, and also silicon or lithium metal. It protects the electrode from further reaction but grows slowly for the whole life of the cell, consuming cyclable lithium.",
        "related": [
          "passivation",
          "formation",
          "calendar-aging",
          "loss-of-lithium-inventory",
          "cei"
        ],
        "lesson": "fundamentals/battery-aging/#sei",
        "url": "https://lemonergy.com/learn/glossary/sei/",
        "mentions": [
          "electrode",
          "graphite",
          "electrolyte"
        ]
      }
    },
    {
      "id": "term:lipf6",
      "type": "Term",
      "label": "Lithium hexafluorophosphate",
      "properties": {
        "id": "lipf6",
        "name": "Lithium hexafluorophosphate",
        "abbr": "LiPF₆",
        "section": "topic-electrolytes",
        "definition": "The lithium salt in nearly every commercial electrolyte, chosen for conductivity, aluminium passivation and cost rather than stability: it decomposes above about 60 °C and reacts with water to form HF.",
        "related": [
          "lithium-salt",
          "hydrofluoric-acid",
          "lifsi",
          "dry-room",
          "aluminium-foil"
        ],
        "url": "https://lemonergy.com/learn/glossary/lipf6/",
        "mentions": [
          "electrolyte",
          "passivation"
        ]
      }
    }
  ]
}