{
  "node": {
    "id": "term:gas-chromatography-mass-spectrometry",
    "type": "Term",
    "label": "Gas chromatography–mass spectrometry",
    "properties": {
      "id": "gas-chromatography-mass-spectrometry",
      "name": "Gas chromatography–mass spectrometry",
      "abbr": "GC-MS",
      "aka": [
        "gas chromatography",
        "GC"
      ],
      "section": "topic-analysis",
      "definition": "Separating the volatile components of a sample in a heated column and identifying each by its mass spectrum. It measures electrolyte composition and aging products such as transesterified solvents and oligomers; with thermal-conductivity detection it also quantifies hydrogen, carbon monoxide, carbon dioxide and hydrocarbons in cell and vent gas.",
      "related": [
        "electrolyte-decomposition",
        "off-gas",
        "gas-generation",
        "differential-electrochemical-mass-spectrometry",
        "post-mortem"
      ],
      "url": "https://lemonergy.com/learn/glossary/gas-chromatography-mass-spectrometry/",
      "mentions": [
        "electrolyte"
      ]
    }
  },
  "edges": [
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    {
      "id": "edge:5585",
      "source": "term:gas-chromatography-mass-spectrometry",
      "target": "term:electrolyte-decomposition",
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      "source": "term:gas-chromatography-mass-spectrometry",
      "target": "term:gas-generation",
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      "source": "term:gas-chromatography-mass-spectrometry",
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      "source": "term:gas-chromatography-mass-spectrometry",
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      "id": "topic:topic-analysis",
      "type": "Topic",
      "label": "Materials analysis and post-mortem",
      "properties": {
        "id": "topic-analysis",
        "name": "Materials analysis and post-mortem",
        "lede": "The laboratory techniques that look inside electrodes, interphases and electrolytes to see what a cell is made of and how it aged.",
        "context": "Connect results with scale and specimen preparation.",
        "example": "Surface and bulk measurements may find different compositions in the same electrode without contradiction.",
        "lesson_url": "https://lemonergy.com/learn/labs/battery-materials-lab/",
        "lesson_label": "Open materials lab"
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    {
      "id": "term:electrolyte-decomposition",
      "type": "Term",
      "label": "Electrolyte decomposition",
      "properties": {
        "id": "electrolyte-decomposition",
        "name": "Electrolyte decomposition",
        "section": "topic-aging",
        "definition": "Reduction of the electrolyte at the negative electrode and oxidation at the positive, outside its stability window. A little is useful — it builds the SEI — but continued decomposition consumes lithium, dries the cell and makes gas.",
        "related": [
          "sei",
          "cei",
          "electrochemical-stability-window",
          "gas-generation",
          "electrolyte-dry-out"
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          "electrode",
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          "electrolyte",
          "oxidation",
          "reduction"
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      "id": "term:off-gas",
      "type": "Term",
      "label": "Off-gas",
      "properties": {
        "id": "off-gas",
        "name": "Off-gas",
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          "vent gas"
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        "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"
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        "mentions": [
          "electrolyte"
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    {
      "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",
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          "vent",
          "formation"
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        "url": "https://lemonergy.com/learn/glossary/gas-generation/",
        "mentions": [
          "electrolyte",
          "pouch-cell"
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    },
    {
      "id": "term:differential-electrochemical-mass-spectrometry",
      "type": "Term",
      "label": "Differential electrochemical mass spectrometry",
      "properties": {
        "id": "differential-electrochemical-mass-spectrometry",
        "name": "Differential electrochemical mass spectrometry",
        "abbr": "DEMS",
        "aka": [
          "OEMS",
          "online electrochemical mass spectrometry"
        ],
        "section": "topic-analysis",
        "definition": "Feeding gas from an operating cell straight into a mass spectrometer, so each species is identified and quantified as it forms. It shows ethylene from ethylene carbonate reduction during formation, and the oxygen and carbon dioxide released by layered oxides at high state of charge, tying each gas to the voltage that made it.",
        "related": [
          "gas-generation",
          "off-gas",
          "electrolyte-decomposition",
          "formation",
          "operando-measurement",
          "gas-chromatography-mass-spectrometry"
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        "url": "https://lemonergy.com/learn/glossary/differential-electrochemical-mass-spectrometry/",
        "mentions": [
          "state-of-charge",
          "reduction",
          "ec"
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    {
      "id": "term:post-mortem",
      "type": "Term",
      "label": "Post-mortem analysis",
      "properties": {
        "id": "post-mortem",
        "name": "Post-mortem analysis",
        "aka": [
          "teardown"
        ],
        "section": "topic-analysis",
        "definition": "Opening an aged or failed cell in an inert glovebox and examining its electrodes by microscopy, diffraction and chemical analysis. It confirms which degradation mechanisms actually occurred rather than inferring them from voltage.",
        "related": [
          "aging-mechanism",
          "scanning-electron-microscopy",
          "x-ray-diffraction",
          "differential-voltage-analysis",
          "nuclear-magnetic-resonance"
        ],
        "url": "https://lemonergy.com/learn/glossary/post-mortem/",
        "mentions": []
      }
    },
    {
      "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"
        ]
      }
    }
  ]
}