{
  "node": {
    "id": "term:swelling",
    "type": "Term",
    "label": "Swelling",
    "properties": {
      "id": "swelling",
      "name": "Swelling",
      "section": "topic-aging",
      "definition": "Growth in a cell’s thickness, reversibly as the electrodes expand on charge and irreversibly as gas and SEI accumulate. Packs allow for it with compression pads, and a sudden swell in service is a warning sign.",
      "related": [
        "gas-generation",
        "pouch-cell",
        "silicon-anode",
        "stack-pressure",
        "compression-pad",
        "swelling-test"
      ],
      "url": "https://lemonergy.com/learn/glossary/swelling/",
      "mentions": [
        "sei"
      ]
    }
  },
  "edges": [
    {
      "id": "edge:1524",
      "source": "term:swelling",
      "target": "topic:topic-aging",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
      }
    },
    {
      "id": "edge:1525",
      "source": "term:swelling",
      "target": "term:gas-generation",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:1526",
      "source": "term:swelling",
      "target": "term:pouch-cell",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:1527",
      "source": "term:swelling",
      "target": "term:silicon-anode",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:1528",
      "source": "term:swelling",
      "target": "term:stack-pressure",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:1529",
      "source": "term:swelling",
      "target": "term:compression-pad",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:1530",
      "source": "term:swelling",
      "target": "term:swelling-test",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:mentions/swelling/sei",
      "source": "term:swelling",
      "target": "term:sei",
      "type": "mentions",
      "properties": {
        "sourceFile": "terms.json",
        "method": "build_glossary.mention_index + mentions",
        "field": "definition",
        "meaning": "Text mention; not a causal claim"
      }
    },
    {
      "id": "edge:1532",
      "source": "term:swelling",
      "target": "reference:edge-degradation",
      "type": "cites",
      "properties": {
        "sourceFile": "wiki-references.json",
        "scope": "direct technical reference"
      }
    }
  ],
  "neighbors": [
    {
      "id": "topic:topic-aging",
      "type": "Topic",
      "label": "Aging and degradation",
      "properties": {
        "id": "topic-aging",
        "name": "Aging and degradation",
        "lede": "Why a cell loses capacity and gains resistance, and the mechanisms behind it.",
        "context": "Separate mechanisms, observations and fitted models.",
        "example": "Capacity loss and resistance rise can have different causes; a film-growth curve cannot identify both.",
        "lesson_url": "https://lemonergy.com/learn/fundamentals/battery-aging/",
        "lesson_label": "Open aging"
      }
    },
    {
      "id": "term:gas-generation",
      "type": "Term",
      "label": "Gas generation",
      "properties": {
        "id": "gas-generation",
        "name": "Gas generation",
        "aka": [
          "gassing"
        ],
        "section": "topic-aging",
        "definition": "Formation of gases — ethylene, hydrogen, carbon monoxide and carbon dioxide — by electrolyte decomposition, mostly during formation and later under high voltage or temperature. In a pouch cell it shows as swelling; in a can it raises pressure until the vent opens.",
        "related": [
          "swelling",
          "degassing",
          "electrolyte-decomposition",
          "vent",
          "formation"
        ],
        "lesson": "fundamentals/battery-aging/#gas",
        "url": "https://lemonergy.com/learn/glossary/gas-generation/",
        "mentions": [
          "electrolyte",
          "pouch-cell"
        ]
      }
    },
    {
      "id": "term:pouch-cell",
      "type": "Term",
      "label": "Pouch cell",
      "properties": {
        "id": "pouch-cell",
        "name": "Pouch cell",
        "aka": [
          "lithium polymer cell",
          "LiPo"
        ],
        "section": "topic-chemistries",
        "definition": "A cell sealed in a flexible bag of aluminium laminated with plastic, holding stacked electrode sheets in larger cells or a flattened wound roll in many small ones. It is light and easy to cool, but needs outside support and can visibly swell if gas forms inside.",
        "related": [
          "pouch-foil",
          "stacking",
          "swelling",
          "degassing",
          "prismatic-cell"
        ],
        "lesson": "fundamentals/cell-production/#formats",
        "example": {
          "title": "Include mechanical support",
          "text": "A pouch encloses layered electrodes. Support provided by the module is part of the complete design, separate from the active layers."
        },
        "url": "https://lemonergy.com/learn/glossary/pouch-cell/",
        "mentions": [
          "electrode"
        ]
      }
    },
    {
      "id": "term:silicon-anode",
      "type": "Term",
      "label": "Silicon anode",
      "properties": {
        "id": "silicon-anode",
        "name": "Silicon anode",
        "aka": [
          "silicon-graphite",
          "SiOx"
        ],
        "section": "topic-components",
        "definition": "A negative electrode that uses silicon, which alloys with lithium and stores roughly ten times more charge per gram than graphite but swells by up to 300 %. Today it is blended into graphite at a few percent to limit the swelling.",
        "related": [
          "graphite",
          "alloying",
          "particle-cracking",
          "swelling",
          "self-healing-binder"
        ],
        "example": {
          "title": "Read the mixture basis",
          "text": "A silicon-containing electrode may be a blend rather than pure silicon. A silicon percentage needs a clear mass basis."
        },
        "url": "https://lemonergy.com/learn/glossary/silicon-anode/",
        "mentions": [
          "electrode",
          "negative-electrode"
        ]
      }
    },
    {
      "id": "term:stack-pressure",
      "type": "Term",
      "label": "Stack pressure",
      "properties": {
        "id": "stack-pressure",
        "name": "Stack pressure",
        "section": "topic-manufacturing",
        "definition": "Pressure applied to a cell stack, in production or in use, to keep its layers in contact. Solid-state cells depend on it, because ions can only cross where two solids touch.",
        "unit": "MPa",
        "related": [
          "solid-state-battery",
          "solid-electrolyte",
          "compression-pad",
          "swelling"
        ],
        "lesson": "fundamentals/solid-state-cell-production/#contact",
        "url": "https://lemonergy.com/learn/glossary/stack-pressure/",
        "mentions": [
          "cell-stack"
        ]
      }
    },
    {
      "id": "term:compression-pad",
      "type": "Term",
      "label": "Compression pad",
      "properties": {
        "id": "compression-pad",
        "name": "Compression pad",
        "aka": [
          "foam pad",
          "swelling pad"
        ],
        "section": "topic-pack",
        "definition": "A foam sheet between pouch or prismatic cells that keeps a defined pressure on them as they breathe on charge and swell with age. It also provides some thermal separation between neighbours.",
        "related": [
          "swelling",
          "stack-pressure",
          "thermal-barrier",
          "pouch-cell"
        ],
        "url": "https://lemonergy.com/learn/glossary/compression-pad/",
        "mentions": []
      }
    },
    {
      "id": "term:swelling-test",
      "type": "Term",
      "label": "Swelling test",
      "properties": {
        "id": "swelling-test",
        "name": "Swelling test",
        "aka": [
          "constant-pressure swelling test",
          "constant-volume swelling test",
          "swelling force test",
          "thickness growth test"
        ],
        "section": "topic-testing",
        "definition": "Measuring how a cell grows during cycling or storage in one of two fixtures: constant pressure, where springs or a pneumatic press hold a set force and the thickness change is logged, or constant volume, where rigid plates fix the gap and the rising force is logged. Module designers need both to size end plates and compression pads.",
        "related": [
          "swelling",
          "stack-pressure",
          "compression-pad",
          "pouch-cell",
          "gas-generation"
        ],
        "url": "https://lemonergy.com/learn/glossary/swelling-test/",
        "mentions": []
      }
    },
    {
      "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": "reference:edge-degradation",
      "type": "Reference",
      "label": "Lithium ion battery degradation: what you need to know",
      "properties": {
        "title": "Lithium ion battery degradation: what you need to know",
        "publisher": "Physical Chemistry Chemical Physics",
        "url": "https://doi.org/10.1039/D1CP00359C",
        "type": "Review article",
        "scope": "Degradation mechanisms, modes, operational effects and their interactions.",
        "year": 2021,
        "accessed": "2026-10-27"
      }
    }
  ]
}