{ "node": { "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" ] } }, "edges": [ { "id": "edge:1127", "source": "term:polarization", "target": "topic:topic-charging", "type": "belongsTo", "properties": { "sourceFile": "terms.json" } }, { "id": "edge:1128", "source": "term:polarization", "target": "term:overpotential", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:1129", "source": "term:polarization", "target": "term:ir-drop", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:1130", "source": "term:polarization", "target": "term:concentration-polarization", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:1131", "source": "term:polarization", "target": "term:open-circuit-voltage", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:1132", "source": "term:polarization", "target": "term:polarisation-curve", "type": "relatedTo", "properties": { "sourceFile": "terms.json", "meaning": "Related context; not a causal claim" } }, { "id": "edge:mentions/polarization/voltage", "source": "term:polarization", "target": "term:voltage", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:mentions/polarization/closed-circuit-voltage", "source": "term:polarization", "target": "term:closed-circuit-voltage", "type": "mentions", "properties": { "sourceFile": "terms.json", "method": "build_glossary.mention_index + mentions", "field": "definition", "meaning": "Text mention; not a causal claim" } }, { "id": "edge:1135", "source": "term:polarization", "target": "visual:rc", "type": "illustratedBy", "properties": { "sourceFile": "visual-pages.json" } } ], "neighbors": [ { "id": "topic:topic-charging", "type": "Topic", "label": "Charging and discharging", "properties": { "id": "topic-charging", "name": "Charging and discharging", "lede": "How current goes in and comes out, and the limits that stop it.", "context": "Separate regulation from availability.", "example": "The same CC–CV law can operate overnight or during a short depot stop.", "lesson_url": "https://lemonergy.com/learn/fundamentals/capacity-and-c-rate/", "lesson_label": "Open charging quantities" } }, { "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:ir-drop", "type": "Term", "label": "IR drop", "properties": { "id": "ir-drop", "name": "IR drop", "aka": [ "ohmic drop", "voltage sag" ], "section": "topic-charging", "definition": "The instant step in terminal voltage when current starts or stops, equal to current times internal resistance. It is lost as heat and is the reason a cell’s voltage under load sits below its open-circuit voltage.", "formula": "ΔV = I × R", "unit": "V", "related": [ "internal-resistance", "ohms-law", "polarization", "open-circuit-voltage" ], "example": { "title": "Distinguish a current step from SOC change", "text": "When discharge current jumps from 0 A to 10 A through an illustrative 20 mΩ resistance, terminal voltage immediately drops by 0.2 V. Slower polarization and SOC change are separate effects." }, "url": "https://lemonergy.com/learn/glossary/ir-drop/", "mentions": [ "voltage", "closed-circuit-voltage" ] } }, { "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: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: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" ] } }, { "id": "term:voltage", "type": "Term", "label": "Voltage", "properties": { "id": "voltage", "name": "Voltage", "aka": [ "terminal voltage" ], "section": "topic-units", "definition": "The potential difference between a cell’s two terminals. It comes from the chemical difference between the electrodes, moves with state of charge, and sags under load because of internal resistance.", "unit": "V", "related": [ "open-circuit-voltage", "nominal-voltage", "internal-resistance", "ir-drop" ], "lesson": "fundamentals/cell-anatomy/#voltage", "url": "https://lemonergy.com/learn/glossary/voltage/", "mentions": [ "state-of-charge" ] } }, { "id": "term:closed-circuit-voltage", "type": "Term", "label": "Closed-circuit voltage", "properties": { "id": "closed-circuit-voltage", "name": "Closed-circuit voltage", "abbr": "CCV", "aka": [ "loaded voltage", "voltage under load" ], "section": "topic-units", "definition": "The terminal voltage while current flows, lower than the open-circuit voltage by the polarization. It is what the system actually sees, and the difference between the two is a direct measure of the cell’s resistance.", "unit": "V", "related": [ "open-circuit-voltage", "polarization", "ir-drop", "voltage" ], "url": "https://lemonergy.com/learn/glossary/closed-circuit-voltage/", "mentions": [] } }, { "id": "visual:rc", "type": "Visual", "label": "Voltage response and relaxation", "properties": { "title": "Voltage response and relaxation", "summary": "One time constant completes about 63% of a first-order voltage change.", "readout": "At τ = 20 s, 63.2% of the step response is complete; a relaxation retains 36.8%.", "formula": "τ = RC; step response = 1 − e^(−t/τ)", "note": "Two separate analytical experiments; normalized voltage, not measured data.", "software": { "status": "reference", "label": "Reference concept", "body": "An analytical RC response explains polarization and relaxation. It is not an identified RC network or a native Studio battery capability.", "href": "../chapter-1/" }, "html": "
First-order voltage response
First-order voltage responseTime (s) versus Fraction of voltage change. Step response; Separate relaxation experiment. Interpretation follows the graphs.000.263450.525900.7881351.05180Time (s)Fraction of voltagechange
Step responseSeparate relaxation experiment (dashed)
" } } ] }