{
  "node": {
    "id": "term:homo-lumo",
    "type": "Term",
    "label": "HOMO–LUMO gap",
    "properties": {
      "id": "homo-lumo",
      "name": "HOMO–LUMO gap",
      "aka": [
        "HOMO",
        "LUMO",
        "frontier orbitals",
        "highest occupied molecular orbital",
        "lowest unoccupied molecular orbital"
      ],
      "section": "topic-electrochemistry",
      "definition": "The energy gap between a molecule’s highest occupied and lowest unoccupied orbitals, used to screen electrolyte components. A solvent whose LUMO lies below the negative electrode’s Fermi level is reduced, and one whose HOMO lies above the positive electrode’s is oxidised; additives such as vinylene carbonate are chosen to reduce before the main solvent and build the SEI.",
      "related": [
        "electrochemical-stability-window",
        "sei",
        "electrolyte-additive",
        "vc",
        "electrolyte-decomposition"
      ],
      "url": "https://lemonergy.com/learn/glossary/homo-lumo/",
      "mentions": [
        "electrode",
        "negative-electrode",
        "positive-electrode",
        "electrolyte"
      ]
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      "target": "term:electrochemical-stability-window",
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        "meaning": "Related context; not a causal claim"
      }
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      "id": "edge:6716",
      "source": "term:homo-lumo",
      "target": "term:sei",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
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      "id": "edge:6717",
      "source": "term:homo-lumo",
      "target": "term:electrolyte-additive",
      "type": "relatedTo",
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        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
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      "id": "edge:6718",
      "source": "term:homo-lumo",
      "target": "term:vc",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:6719",
      "source": "term:homo-lumo",
      "target": "term:electrolyte-decomposition",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:mentions/homo-lumo/electrode",
      "source": "term:homo-lumo",
      "target": "term:electrode",
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      "id": "edge:mentions/homo-lumo/negative-electrode",
      "source": "term:homo-lumo",
      "target": "term:negative-electrode",
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      "id": "edge:mentions/homo-lumo/positive-electrode",
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        "field": "definition",
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      "id": "edge:mentions/homo-lumo/electrolyte",
      "source": "term:homo-lumo",
      "target": "term:electrolyte",
      "type": "mentions",
      "properties": {
        "sourceFile": "terms.json",
        "method": "build_glossary.mention_index + mentions",
        "field": "definition",
        "meaning": "Text mention; not a causal claim"
      }
    }
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    {
      "id": "topic:topic-electrochemistry",
      "type": "Topic",
      "label": "Electrochemistry fundamentals",
      "properties": {
        "id": "topic-electrochemistry",
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        "lede": "The reactions and potentials that make a cell a battery.",
        "context": "Connect reaction sites and transport paths.",
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        "lesson_url": "https://lemonergy.com/learn/fundamentals/cell-anatomy/",
        "lesson_label": "Open cell anatomy"
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      "id": "term:electrochemical-stability-window",
      "type": "Term",
      "label": "Electrochemical stability window",
      "properties": {
        "id": "electrochemical-stability-window",
        "name": "Electrochemical stability window",
        "section": "topic-electrochemistry",
        "definition": "The potential range within which an electrolyte is neither reduced nor oxidised. Carbonate electrolytes are only stable from about 1 V to 4.3 V vs Li/Li⁺; graphite operates below that, which is why the SEI, not thermodynamics, keeps the cell alive.",
        "unit": "V",
        "related": [
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          "sei",
          "voltage-window",
          "lnmo",
          "homo-lumo"
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        "url": "https://lemonergy.com/learn/glossary/electrochemical-stability-window/",
        "mentions": [
          "graphite",
          "electrolyte"
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    },
    {
      "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"
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        "url": "https://lemonergy.com/learn/glossary/sei/",
        "mentions": [
          "electrode",
          "graphite",
          "electrolyte"
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    {
      "id": "term:electrolyte-additive",
      "type": "Term",
      "label": "Electrolyte additive",
      "properties": {
        "id": "electrolyte-additive",
        "name": "Electrolyte additive",
        "aka": [
          "VC",
          "FEC"
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        "section": "topic-electrolytes",
        "definition": "A compound added to the electrolyte at a few percent to improve one property — vinylene carbonate and fluoroethylene carbonate build a tougher SEI, others suppress gassing or overcharge. Additive packages are among a cell maker’s closest secrets.",
        "related": [
          "electrolyte",
          "sei",
          "formation",
          "gas-generation",
          "libob"
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        "mentions": [
          "overcharge",
          "vc",
          "fec"
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      }
    },
    {
      "id": "term:vc",
      "type": "Term",
      "label": "Vinylene carbonate",
      "properties": {
        "id": "vc",
        "name": "Vinylene carbonate",
        "abbr": "VC",
        "section": "topic-electrolytes",
        "definition": "The most common SEI-forming additive, used at 1–3 %. It is reduced before the solvent on the first charge and polymerises into a thinner, more flexible SEI that lengthens cycle life.",
        "related": [
          "electrolyte-additive",
          "sei",
          "fec",
          "formation"
        ],
        "url": "https://lemonergy.com/learn/glossary/vc/",
        "mentions": [
          "cycle-life"
        ]
      }
    },
    {
      "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"
        ],
        "url": "https://lemonergy.com/learn/glossary/electrolyte-decomposition/",
        "mentions": [
          "electrode",
          "negative-electrode",
          "electrolyte",
          "oxidation",
          "reduction"
        ]
      }
    },
    {
      "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"
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        "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"
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    },
    {
      "id": "term:negative-electrode",
      "type": "Term",
      "label": "Negative electrode",
      "properties": {
        "id": "negative-electrode",
        "name": "Negative electrode",
        "section": "topic-components",
        "definition": "The electrode at the lower potential, usually graphite on copper foil in a lithium-ion cell. It holds the lithium when the cell is charged and releases it on discharge, and industry calls it the anode.",
        "related": [
          "anode",
          "graphite",
          "positive-electrode",
          "copper-foil"
        ],
        "lesson": "fundamentals/cell-anatomy/#anode-cathode",
        "example": {
          "title": "Keep the polarity name",
          "text": "Graphite remains the negative electrode during charge and discharge, while the anode/cathode reaction labels change with operating direction."
        },
        "url": "https://lemonergy.com/learn/glossary/negative-electrode/",
        "mentions": [
          "electrode"
        ]
      }
    },
    {
      "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"
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      }
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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",
          "ionic-liquid-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"
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    }
  ]
}