{
  "node": {
    "id": "term:polarisation-curve",
    "type": "Term",
    "label": "Polarisation curve",
    "properties": {
      "id": "polarisation-curve",
      "name": "Polarisation curve",
      "aka": [
        "polarization curve",
        "V–I curve",
        "current–voltage curve"
      ],
      "section": "topic-electrochemistry",
      "definition": "A plot of cell voltage against current or current density, showing how far voltage falls below its open-circuit value as load rises. Standard for fuel cells, it shows three regions: a steep early drop from activation losses, a straight ohmic section, and a final collapse when mass transport cannot keep up. For batteries it is built from pulse tests.",
      "related": [
        "polarization",
        "overpotential",
        "concentration-polarization",
        "fuel-cell",
        "pulse-test",
        "open-circuit-voltage"
      ],
      "url": "https://lemonergy.com/learn/glossary/polarisation-curve/",
      "mentions": [
        "cell-voltage"
      ]
    }
  },
  "edges": [
    {
      "id": "edge:6724",
      "source": "term:polarisation-curve",
      "target": "topic:topic-electrochemistry",
      "type": "belongsTo",
      "properties": {
        "sourceFile": "terms.json"
      }
    },
    {
      "id": "edge:6725",
      "source": "term:polarisation-curve",
      "target": "term:polarization",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:6726",
      "source": "term:polarisation-curve",
      "target": "term:overpotential",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:6727",
      "source": "term:polarisation-curve",
      "target": "term:concentration-polarization",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:6728",
      "source": "term:polarisation-curve",
      "target": "term:fuel-cell",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:6729",
      "source": "term:polarisation-curve",
      "target": "term:pulse-test",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:6730",
      "source": "term:polarisation-curve",
      "target": "term:open-circuit-voltage",
      "type": "relatedTo",
      "properties": {
        "sourceFile": "terms.json",
        "meaning": "Related context; not a causal claim"
      }
    },
    {
      "id": "edge:mentions/polarisation-curve/cell-voltage",
      "source": "term:polarisation-curve",
      "target": "term:cell-voltage",
      "type": "mentions",
      "properties": {
        "sourceFile": "terms.json",
        "method": "build_glossary.mention_index + mentions",
        "field": "definition",
        "meaning": "Text mention; not a causal claim"
      }
    }
  ],
  "neighbors": [
    {
      "id": "topic:topic-electrochemistry",
      "type": "Topic",
      "label": "Electrochemistry fundamentals",
      "properties": {
        "id": "topic-electrochemistry",
        "name": "Electrochemistry fundamentals",
        "lede": "The reactions and potentials that make a cell a battery.",
        "context": "Connect reaction sites and transport paths.",
        "example": "A circuit can predict terminal voltage while leaving electrode potentials and reaction kinetics unresolved.",
        "lesson_url": "https://lemonergy.com/learn/fundamentals/cell-anatomy/",
        "lesson_label": "Open cell anatomy"
      }
    },
    {
      "id": "term:polarization",
      "type": "Term",
      "label": "Polarization",
      "properties": {
        "id": "polarization",
        "name": "Polarization",
        "aka": [
          "overvoltage"
        ],
        "section": "topic-charging",
        "definition": "The gap between a cell’s terminal voltage under load and its open-circuit voltage. It has ohmic, charge-transfer and concentration parts, grows with current and falling temperature, and is where delivered energy is lost.",
        "unit": "V",
        "related": [
          "overpotential",
          "ir-drop",
          "concentration-polarization",
          "open-circuit-voltage",
          "polarisation-curve"
        ],
        "url": "https://lemonergy.com/learn/glossary/polarization/",
        "mentions": [
          "voltage",
          "closed-circuit-voltage"
        ]
      }
    },
    {
      "id": "term:overpotential",
      "type": "Term",
      "label": "Overpotential",
      "properties": {
        "id": "overpotential",
        "name": "Overpotential",
        "abbr": "η",
        "section": "topic-electrochemistry",
        "definition": "The extra voltage, beyond the equilibrium potential, needed to drive a reaction at a given rate at one electrode. Activation overpotential pays for charge transfer, concentration overpotential for depleted reactant, and both appear as polarization at the terminals.",
        "unit": "V",
        "related": [
          "polarization",
          "butler-volmer",
          "exchange-current-density",
          "concentration-polarization"
        ],
        "url": "https://lemonergy.com/learn/glossary/overpotential/",
        "mentions": [
          "electrode",
          "charge-transfer"
        ]
      }
    },
    {
      "id": "term:concentration-polarization",
      "type": "Term",
      "label": "Concentration polarization",
      "properties": {
        "id": "concentration-polarization",
        "name": "Concentration polarization",
        "section": "topic-electrochemistry",
        "definition": "Voltage loss that arises when reactant is consumed faster than diffusion can replace it, so the concentration at the surface differs from the bulk. It dominates at high current and low temperature and recovers slowly when current stops.",
        "related": [
          "polarization",
          "diffusion",
          "overpotential",
          "relaxation",
          "concentration-gradient"
        ],
        "url": "https://lemonergy.com/learn/glossary/concentration-polarization/",
        "mentions": []
      }
    },
    {
      "id": "term:fuel-cell",
      "type": "Term",
      "label": "Fuel cell",
      "properties": {
        "id": "fuel-cell",
        "name": "Fuel cell",
        "section": "topic-other-chemistries",
        "definition": "An electrochemical converter that makes electricity from a fuel, usually hydrogen, and oxygen as long as both are supplied, rather than storing energy in its electrodes. Fuel-cell vehicles still carry a battery to buffer power.",
        "related": [
          "flow-battery",
          "hybrid-vehicle",
          "redox-reaction"
        ],
        "url": "https://lemonergy.com/learn/glossary/fuel-cell/",
        "mentions": []
      }
    },
    {
      "id": "term:pulse-test",
      "type": "Term",
      "label": "Pulse test",
      "properties": {
        "id": "pulse-test",
        "name": "Pulse test",
        "aka": [
          "current pulse test",
          "DC pulse"
        ],
        "section": "topic-testing",
        "definition": "Applying a current step of defined size and duration and recording the voltage response. The instant voltage step gives the ohmic resistance, the following curve the slower polarization; HPPC is a standardised sequence of such pulses across state of charge.",
        "related": [
          "hppc",
          "dcir",
          "internal-resistance",
          "relaxation",
          "equivalent-circuit-model"
        ],
        "url": "https://lemonergy.com/learn/glossary/pulse-test/",
        "mentions": [
          "polarization",
          "state-of-charge"
        ]
      }
    },
    {
      "id": "term:open-circuit-voltage",
      "type": "Term",
      "label": "Open-circuit voltage",
      "properties": {
        "id": "open-circuit-voltage",
        "name": "Open-circuit voltage",
        "abbr": "OCV",
        "section": "topic-state",
        "definition": "The voltage across a cell’s terminals when no current flows and the cell has rested long enough for the voltage to settle. It depends on state of charge and temperature, and a cell whose open-circuit voltage falls unusually fast in storage may have an internal short.",
        "unit": "V",
        "related": [
          "ocv-soc-curve",
          "relaxation",
          "voltage-hysteresis",
          "k-value",
          "internal-short-circuit"
        ],
        "lesson": "fundamentals/cell-production/#finishing",
        "url": "https://lemonergy.com/learn/glossary/open-circuit-voltage/",
        "mentions": [
          "state-of-charge"
        ]
      }
    },
    {
      "id": "term:cell-voltage",
      "type": "Term",
      "label": "Cell voltage",
      "properties": {
        "id": "cell-voltage",
        "name": "Cell voltage",
        "aka": [
          "electromotive force",
          "EMF"
        ],
        "section": "topic-electrochemistry",
        "definition": "The difference between the positive and negative electrode potentials at equilibrium: for NMC against graphite about 3.7 V. It is set by the chemistry, and the difference in Gibbs free energy of the cell reaction per unit charge.",
        "formula": "E = E₊ − E₋ = −ΔG / nF",
        "unit": "V",
        "related": [
          "electrode-potential",
          "gibbs-free-energy",
          "open-circuit-voltage",
          "nominal-voltage"
        ],
        "example": {
          "title": "Subtract equilibrium electrode potentials",
          "text": "If two illustrative electrode potentials are 4.0 V and 0.2 V versus the same reference, their equilibrium cell voltage is 3.8 V. Under load, resistance and polarization change the measured terminal voltage."
        },
        "url": "https://lemonergy.com/learn/glossary/cell-voltage/",
        "mentions": [
          "electrode",
          "negative-electrode",
          "graphite"
        ]
      }
    }
  ]
}