{
  "node": {
    "id": "term:fourier-transform-infrared-spectroscopy",
    "type": "Term",
    "label": "Fourier-transform infrared spectroscopy",
    "properties": {
      "id": "fourier-transform-infrared-spectroscopy",
      "name": "Fourier-transform infrared spectroscopy",
      "abbr": "FTIR",
      "aka": [
        "infrared spectroscopy",
        "IR spectroscopy",
        "ATR-FTIR"
      ],
      "section": "topic-analysis",
      "definition": "Identifying chemical bonds from the infrared wavelengths a sample absorbs. Battery labs use it to fingerprint electrolyte solvents and their ratios, organic SEI species such as lithium alkyl carbonates, and binders; the attenuated-total-reflectance mode probes electrode surfaces directly, and gas cells analyse vent gas online.",
      "related": [
        "x-ray-photoelectron-spectroscopy",
        "sei",
        "electrolyte",
        "electrolyte-decomposition",
        "off-gas"
      ],
      "url": "https://lemonergy.com/learn/glossary/fourier-transform-infrared-spectroscopy/",
      "mentions": [
        "electrode"
      ]
    }
  },
  "edges": [
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      "id": "edge:5577",
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    {
      "id": "edge:5578",
      "source": "term:fourier-transform-infrared-spectroscopy",
      "target": "term:x-ray-photoelectron-spectroscopy",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5579",
      "source": "term:fourier-transform-infrared-spectroscopy",
      "target": "term:sei",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
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    {
      "id": "edge:5580",
      "source": "term:fourier-transform-infrared-spectroscopy",
      "target": "term:electrolyte",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5581",
      "source": "term:fourier-transform-infrared-spectroscopy",
      "target": "term:electrolyte-decomposition",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:5582",
      "source": "term:fourier-transform-infrared-spectroscopy",
      "target": "term:off-gas",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
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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:x-ray-photoelectron-spectroscopy",
      "type": "Term",
      "label": "X-ray photoelectron spectroscopy",
      "properties": {
        "id": "x-ray-photoelectron-spectroscopy",
        "name": "X-ray photoelectron spectroscopy",
        "abbr": "XPS",
        "aka": [
          "ESCA",
          "photoelectron spectroscopy"
        ],
        "section": "topic-analysis",
        "definition": "Shining X-rays on a surface and measuring the energies of the electrons knocked out, which identify each element and its chemical bonding in the top few nanometres. It is the main tool for SEI and CEI composition — LiF, Li₂CO₃, organic carbonates — and, combined with argon-ion sputtering, for depth profiles.",
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          "sei",
          "cei",
          "time-of-flight-sims",
          "post-mortem",
          "fourier-transform-infrared-spectroscopy"
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      "id": "term:sei",
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      "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"
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        "url": "https://lemonergy.com/learn/glossary/sei/",
        "mentions": [
          "electrode",
          "graphite",
          "electrolyte"
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      "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",
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        "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: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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        "url": "https://lemonergy.com/learn/glossary/electrolyte-decomposition/",
        "mentions": [
          "electrode",
          "negative-electrode",
          "electrolyte",
          "oxidation",
          "reduction"
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      }
    },
    {
      "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: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"
        ]
      }
    }
  ]
}